Isco3 - Prismasonic HD-5000R - DIY lens - Zooming method - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #1 of 41 Old 09-28-2010, 02:06 AM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
INTRODUCTION

This is a comparison test between the three different level anamorphic lenses and the zooming method for creating a cinemascope picture. The lenses in a test are Isco3/Schneider Cine-digitar XL, Prismasonic HD-5000R and the uncoated single prisms.

Isco3 has two achromatic, ar-coated cylindrical lenses with a focus correction ring. This lens is widely considered as a reference to all lenses, and this is also the reason why it was taken into this test.

Prismasonic HD-5000R has two ar-coated achromatic prisms combined with the focus correction element.

The third 'lens' is two single prisms with no ar-coatings. It represent the DIY approach, and in addition to zooming method, for many it is the first step towards to scope world.

A common assumption is that the all prism based lenses loose to cylindrical design both in sharpness and CA performance, as well as the brightness and contrast performance. This test shows how the good quality prism lens challenges the 'king' isco3. Also this test shows is it worth to start with a ‘DIY’ route, and how is zooming method managing with the lens setups.



OTHER EQUIPMENTS IN A TEST

The projector in this test is a high brightness Panasonic PT-DW6300ES WXGA DLP projector with 2 lamps. It has specified to have maximum brightness around 6000 ansi lumens. In this test it was running with only one lamp in a high contrast mode (mechanical iris close). This was enough to form a picture of good brightness in a pretty small testing room (throw distance 3.3 meters). On the other hand the light output is good to be high enough so that especially with the contrast measurements, the slight room condition changes, if such happen, will not affect to the results. The right side of a projected picture was used in screen shots. It is very clean and absolutely free from any kind of color fringing. On the other hand, since the chromatic aberration of lens attachments mainly occurs on horizontal sides, this area instead of the horizontal center shows the differences best .

The test pictures were thrown to the matte painted white wall. Because the light meter is measuring the values in front of the ‘screen’, it does not matter what are the screen properties.

The room is an ambient light controlled, but the walls are not very dark. This makes the ANSI contrast results worse than in the room of black walls. However, this test is not for defining projector’s absolute performance, but comparing the different scope setups to each other.

The used light meter is AMPROBE LM-120 with specified resolution of 0.01 lux.


BRIGHTNESS, CONTRAST (on/off), CONTRAST (ansi)

All of these measurements are very sensitive to the following things, and the extra attention was paid for them. Optics has to be absolutely free from dirt and especially from grease. Before the tests all the optics were carefully cleaned with Isopropanol, which is a very good solvent for the grease. Secondly, in order results to be comparable, the room, projector and the light meter conditions have to be unchangeable during and between all the tests and setups. The room and projector’s conditions were tested to be unchangeable every time after changing the setup from one to another. This was done by measuring both full ON and full OFF values from the same spot of the same test pictures (without the lens and with same throw ratio).

Brightness

The brightness (full ON) measurements were done with the following test picture.

http://www.prismasonic.com/images/te...FWFwguages.jpg

There are 9 spots from where the results are collected, and the mean (average) is calculated from the samples. In order results to be most comparable to each other, the final results are presented in lux*m^2=lumen. Due to this the mean value of light meter result is yet multiplied by the active picture area. The standard deviation of the 9 sample values is informed similarly in lumen.

In order to get the scope aspect to all 4 setups, for the zooming method measurements the picture was vertically compressed 33% by the projector. Also since Prismasonic can be internally adjusted to ‘pass mode’, this was added to the measurements. As for a reference to this also the uncompressed 16:9 picture without the lens (pass mode for isco+sled) was tested.

The Projector’s throw distance is the same for all measurements (3.3 meters). All the lens setups were measured with a 2.4 throw ratio (zoom factor). The used throw ratio for zooming method was 1.8, because with this ratio the active picture size is about the same as with the lens setups.

Here are the results of the brightness measurements

Isco 3 (TR 2.4)
Mean: 444 lm
Standard deviation: 38 lm

Prismasonic HD-5000R (TR 2.4)
Mean: 427 lm
Standard deviation: 38 lm

DIY lens (TR 2.4)
Mean: 364 lm
Standard deviation: 41 lm

Zooming method (TR 1.8)
Mean: 415 lm
Standard deviation: 53 lm
--------------------------------

Pass mode, ISCO+SLED (TR 2.4)
Mean: 453 lm
Standard deviation: 32 lm

Pass mode, HD-5000R (TR 2.4)
Mean: 438 lm
Standard deviation: 31 lm

Contrast (ON/OFF)

The ON/OFF contrast is defined by the ratio of the maximum brightness and the minimum brightness. This measurement uses the mean results of brightness measurements as ON values in lux. In addition to this, with each setup the full OFF values are measured from the full black picture.

The three measurement points in picture diagonal were taped to the wall. These measure spots for each setup are determined from the 3 squares (left-down, middle, and up-right) of the corresponding brightness measurements setup. The mean OFF value is calculated from the samples, after which the contrast (on-off) can be calculated.

The results are as follows:

Isco 3 (TR 2.4)
Contrast (ON/OFF): 944

Prismasonic HD-5000R (TR 2.4)
Contrast (ON/OFF): 964

DIY LENS (TR 2.4)
Contrast (ON/OFF): 917

Zooming method: (TR 1.8)
Contrast (ON/OFF): 839
--------------------------------

Pass mode, ISCO+SLED (TR 2.4)
Contrast (ON/OFF): 870

Pass mode, HD-5000R (TR 2.4)
Contrast (ON/OFF): 915


Contrast (ANSI)

The ANSI contrast is defined by the ratio of maximum brightness again divided by the minimum brightness. However, this time the minimum brightness is measured from the following picture, where there are both white and black areas in a picture.

http://www.prismasonic.com/images/te...erboard4x4.jpg

The values of white areas were so close to the values measured from the full white picture so that this once again uses the mean results of brightness measurements as full ON values in lux. However, the measures of black areas differ much from the full OFF values due to many reasons, which are for example the projector's technology, projector’s optics, wall and ceiling reflections, the reflections introduced by the anamorphic lens. In this measurement we only are interested in the reflections introduced by the anamorphic lens, supposing that everything else maintains constant during the measurements of all setups.

There are four measurement points from left-down to up-right (black boxes in picture diagonal). While measuring these blocks one has to be very careful in trying to avoid blocking the white blocks as little as possible. It is also important to position oneself with a light meter as similarly as possible in each setup. The mean value is again calculated from the 4 samples, before defining the ratio.

The results are as follows:

Isco 3 (TR 2.4)
Contrast (ANSI): 86

Prismasonic HD-5000R (TR 2.4)
Contrast (ANSI): 87

DIY LENS (TR 2.4)
Contrast (ANSI): 76

Zooming method: (TR 1.8)
Contrast (ANSI): 88
--------------------------

Pass mode, ISCO+SLED (TR 2.4)
Contrast (ANSI): 99

Pass mode, HD-5000R (TR 2.4)
Contrast (ANSI): 98


Conclusions

Due to 33% extra active resolution a good quality anamorphic lens increases the brightness to the scope picture. The brightness increase would have been more significant if the 2.4 ratio would also be used with the zooming method measurement. However, since it is ZOOMING method, it was reasoned to use the throw ratio, which introduces the same height to the scope picture as to full panel 16:9 picture without zooming. Also as mentioned before, with 1.8 throw ratio, the picture size from the same throw distance was about the same as with the lens setups.

The on/off contrast was better with all the lens setups compared to the zooming method. However, in the ansi contrast measurement the zooming method was a winner with a very small margin to Prismasonic and Isco.

In the lens setups the Isco 3 and Prismasonic HD-5000R were very equal in all measurements. Isco created a brighter picture but in the contrast measurements Prismasonic was slightly better. However, the results were so close to each other so that the margin of error could have flipped the results, especially in case of ansi contrast measurement. The ‘DIY’ lens was performing clearly worse in every section.

The following graph represents the measured air-glass reflection curves in % for the 4 samples of Prismasonic HD-5000 series prisms, picked from the manufacturing batch after the AR-coating process.




GEOMETRICAL DISTORTION AND GRID DISTORTION

With all a-lens setups the geometrical as well as the grid distortion (side-to-side linearity) are very much the same. The geometrical distortion for the horizontal expansion lenses is a pincushion type distortion (sides are taller than the center). These both distortions are directly dependent on the throw ratio. With the throw ratio of 2.4 the geometrical distortion for all lenses is around 1.8 %, while with the throw ratio of 1.8 it is around 2.7%. Accordingly with throw ratio of 2.4, the grid distortion for all lenses is around 9%, and with the throw ratio of 1.8 it is 17%. A curved screen with an appropriate curvature radius corrects both of these distortions, and that is why there is a good reason to use one with the lens.


SCREEN SHOTS

The screen shots of 4 different setups are shown below. The source material is the following 1280 x 720 picture.

http://www.prismasonic.com/images/te... shot eye2.jpg

The 'eye box' is located to the horizontal side of the screen, where the chromatic aberration mostly appears. The throw ratio for the lens setups was again 2.4, thus allowing to use enough zoom for zooming method to enlarge the picture to the same size as with the lens setups. Also for the zooming method, the test picture was compressed vertically 33% by the projector.

The isco screen shot shows, why the lens is considered as a very good product. The absence of CA combined with a great sharpness can well be observed from the shot. However, the amount of an anamorphic stretch is dependent on the throw ratio and the throw distance. Thus the focus sweet spot for this setup resulted only around 1.3x stretch instead of intended 1.33x. That is the reason why the 'eye box' is narrower than with the other setups. The correct 1.33x stretch factor was achieved with the throw ratio of 1.8 from this projection distance.

Prismasonic HD-5000R screen shot shows a very good sharpness as well. There exist a small amount of chromatic aberration, which can be seen in white vertical board bars next to black background (max contrast edge), but not very well inside the real picture area, (which also has pretty high contrast edges). It is good to note that LCD projectors normally have more color fringing than this due to the panel misalignment. Prismasonic lens is variable so the correct aspect ratio can always be adjusted.

The DIY lens screen shot differs most from the others. This amount of softness and CA clearly affects to the picture clarity. Without the focus correction optics the horizontal and vertical lines cannot be focused simultaneously, and the sweet spot locates in between thus compromising both the vertical and horizontal sharpness. Also without the proper CA correction the amount of color fringing makes a clear degrease not only to the white board bar but to real picture area as well. However, it is good to note that the test picture window locates on the side, where CA mostly appears. On the horizontal center the picture would be cleaner.

The zooming method represents as the reference for the lenses, when it comes to CA and sharpness. The pixel grid can be noticed better mostly because the vertical pixel density is now around 33% smaller. It is good to note that seeing the pixel structure better does not necessarily mean sharper picture. The fact is that there is no information in a pixel border even if it looks very precise.

Isco 3

Isco 3
------------------------------------
Prismasonic HD-5000R

Prismasonic HD-5000R
----------------------------------------
'DIY' Lens

‘DIY’ Lens
-------------------------------------
Zooming method

Zooming method
--------------------------------------


EDITED 29.9: The Brightness units are now correct, Thanks HogPilot!

Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
Sponsored Links
Advertisement
 
post #2 of 41 Old 09-28-2010, 02:36 AM
AVS Addicted Member
 
Franin's Avatar
 
Join Date: Aug 2007
Location: Western Australia
Posts: 17,091
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 184
Thanks for that Anssi Leppanen. The D.I.Y. lens is it a known lens?

_________________________

Frank

Franin is online now  
post #3 of 41 Old 09-28-2010, 03:58 AM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Franin View Post

Thanks for that Anssi Leppanen. The D.I.Y. lens is it a known lens?

The 'diy' prisms are the same as are used in our most economical H-850 model but without the AR-coatings.

Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
post #4 of 41 Old 09-28-2010, 04:41 AM
AVS Addicted Member
 
Franin's Avatar
 
Join Date: Aug 2007
Location: Western Australia
Posts: 17,091
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 184
Quote:
Originally Posted by prismasonic View Post

The 'diy' prisms are the same as are used in our most economical H-850 model but without the AR-coatings.


Thanks for that.

It's good to see there is good quality lenses out there cylindrical and prisim.

_________________________

Frank

Franin is online now  
post #5 of 41 Old 09-28-2010, 05:45 AM
Advanced Member
 
ilsiu's Avatar
 
Join Date: Jul 2004
Location: Minnesota
Posts: 867
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
First, many thanks to prismasonic for his efforts in objectively characterizing differences between lenses/zooming. Very well done.

I was very surprised to see that on/off CR improves with lenses, and at 12% ~ 14% it's seems to be well outside the measuring instruments margin of error. Do you know if the projector has a constant aperture lens?


Edit: upon further reflection, I think I can answer my own question. The brightness for zoom, 1.8 TR is 415, the brightness for zoom, 2.4 TR (ISCO+sled pass mode) is 453. Since there's a 10% brightness difference by zooming from 1.8 to 2.40 TR, the projector lens must be variable aperture.
ilsiu is offline  
post #6 of 41 Old 09-28-2010, 06:04 AM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by ilsiu View Post

First, many thanks to prismasonic for his efforts in objectively characterizing differences between lenses/zooming. Very well done.

I was very surprised to see that on/off CR improves with lenses, and at 12% ~ 14% it's seems to be well outside the measuring instruments margin of error. Do you know if the projector has a constant aperture lens?


Edit: upon further reflection, I think I can answer my own question. The brightness for zoom, 1.8 TR is 415, the brightness for zoom, 2.4 TR (ISCO+sled pass mode) is 453. Since there's a 10% brightness difference by zooming from 1.8 to 2.40 TR, the projector lens must be variable aperture.

In fact the brightness of zooming method was only 350 lm (-21% from isco) with TR of 2.4. For optical reasons, with the TR of 1.8 the brightness*area becomes higher.

The brightness*area in pass mode (compared to zooming result 415 lm) is better, because now the picture is not compressed and full panel is ON.

Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
post #7 of 41 Old 09-28-2010, 06:46 AM
Advanced Member
 
taffman's Avatar
 
Join Date: Nov 2007
Posts: 651
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Thanks to Prismasonic for that great test report - someone has finally done some meaningful scientific measurements of the A-lens versus the zooming method. As a zoomer I find the results very comforting. The best A-lens only gives about a 7% increase in screen brightness compared with zooming, and zooming has a better Ansi contrast than even the top rated Isco 3. Kind of confirms what many of us zoomers have thought all along.
taffman is offline  
post #8 of 41 Old 09-28-2010, 06:54 AM
AVS Addicted Member
 
Franin's Avatar
 
Join Date: Aug 2007
Location: Western Australia
Posts: 17,091
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 184
Quote:
Originally Posted by taffman View Post

Thanks to Prismasonic for that great test report - someone has finally done some meaningful scientific measurements of the A-lens versus the zooming method. As a zoomer I find the results very comforting. The best A-lens only gives about a 7% increase in screen brightness compared with zooming, and zooming has a better Ansi contrast than even the top rated Isco 3. Kind of confirms what many of us zoomers have thought all along.

Your right Taffman it just shows it's not worth getting a primasonic after all.

_________________________

Frank

Franin is online now  
post #9 of 41 Old 09-28-2010, 07:21 AM
AVS Special Member
 
b curry's Avatar
 
Join Date: Feb 2002
Location: on the way to Hell, Michigan USA
Posts: 2,632
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 31
Would you prefer to have your net worth decrease by 7% or increase by 7%?
b curry is offline  
post #10 of 41 Old 09-28-2010, 07:23 AM
AVS Club Gold
 
HogPilot's Avatar
 
Join Date: Jun 2006
Location: Good Ol' US of A
Posts: 2,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Anssi,

A couple questions about your test:

1. I am confused by your units "lux/m^2" - my understanding is that 1 lux = 1 lumen/m^2, which already takes area into account, so I'm not sure what your unit of lux/m^2 means. You later said that "Due to this the mean value of light meter result is yet multiplied by the active picture area." If you multiply lux by screen area, this gives you lumens - so are you saying your numbers are presented in lux or lumens? Did you mean to say lux * m^2 instead of lux/m^2?

2. Why was the Panasonic PT-DW6300ES - a 1200x800 16:10 business projector with a 0.65" DLP chip - chosen as the test projector? Its poor contrast ratio (rated 2,000:1, measured less) isn't indicative of the much higher CRs available in home theater projectors, and thus doesn't allow you to test lens performance at the very low light levels that we are likely to experience in our home theaters. In addition, business projector optics are generally not nearly as high quality as those offered in even mid-priced home theater projectors - being that this is an optical test, I would expect that you'd want to use something better in terms of chip size/quality and optical properties. Having a quality imaging chip and projector optics are crucial when trying to compare the amount of CA and optical distortion introduced by an anamorphic lens, if we are to test them at their limits. In fact, the no-lens screen shot that you provide shows large amounts of red CA - almost one full pixel width on the left and about a half on top, which is much larger than either the ISCO III or the HD5000R will produce under these conditions! The ISCO III clearly reproduces the red fringe of CA seen in the no-lens picture, whereas the HD5000R shot shows no such fringe. If the screen shots are accurate reproductions of what the lenses are actually doing (i.e. none are out of focus or temporally blurred), this means that the ISCO is simply passing the projector's CA to the screen, whereas the HD5000R is introducing CA which happens to compensate for the projector's CA. Any thoughts on this?

3. Breaking down the numbers behind your on/off contrast measurements, I find the results odd. If I worked the math correctly (based on your throw ratio and distance), your 16:9 screen was 1.375 m X 0.77 m, giving it an area of 1.06 m^2. As I said before, multiplying measured lux by screen area yields lumen output of the projector - from here on out I'll work in lumens since it's a more common unit amongst FP users.

For no lens in place - the "reference measurement" - you measured 481.7 lumens at full brightness and 0.55 lumens at "full black" (rather abysmal black level performance), for an on/off CR of 870:1. With the ISCO III in place, you measured 472.1 lumens at full brightness (1.99% decrease from reference), and 0.50 lumens at "full black" (9.67% decrease from reference) for a CR of 944:1. With the HD5000R in place, you measured 454.1 lumens at full brightness (5.74% decrease from reference) and 0.47 lumens at "full black" (14.93% decrease from reference) for a CR of 964:1.

These numbers don't seem to make sense, in that measured on/off CR actually went up with the lenses in place, and that the black floor dropped with the lenses in place - in both cases, more so with the HD5000R than the ISCO III! Also, the ISCO "lost" almost 5x more light at full black than it did at full white; the HD5000R only "lost" about 2.6x more. Maybe there's some underlying optical mechanism at work here that I don't understand?

4. You readily admitted that your room is already poorly suited for ANSI measurements, which are notoriously hard to accurately attain and reproduce. Things like the light, reflective walls in the room, coupled with the relatively poor optical quality of the business projector you used, don't lend themselves to accurate or useful ANSI measurements. As with the on/off CR measurements, there are plenty of HT owners who have rooms capable of much higher performance than the one you used to perform your measurements. Again, if we are to test these lenses at their limits, controlling all of these variables are important; illustrating that any lens of respectable quality is capable of upholding already poor ANSI CR performance isn't useful to those of us who have rooms and projectors capable of significantly higher performance. Would you agree with this?

Overall it's clear that "bargain" lenses offer significantly poorer performance than more expensive lenses designed and treated to avoid CR and high levels of reflectance. However it seems that your tests aren't conclusive when looking at absolute performance levels of the ISCO III and HD5000R due to the issues I've pointed out above. It seems that you agree with this given your closing remarks, however a more in-depth discussion from you would certainly be welcome!

There are 10 types of people: those who understand binary, and those who don't.

HogPilot is offline  
post #11 of 41 Old 09-28-2010, 07:25 AM
AVS Club Gold
 
HogPilot's Avatar
 
Join Date: Jun 2006
Location: Good Ol' US of A
Posts: 2,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Quote:
Originally Posted by taffman View Post

Thanks to Prismasonic for that great test report - someone has finally done some meaningful scientific measurements of the A-lens versus the zooming method. As a zoomer I find the results very comforting. The best A-lens only gives about a 7% increase in screen brightness compared with zooming, and zooming has a better Ansi contrast than even the top rated Isco 3. Kind of confirms what many of us zoomers have thought all along.

Not quite - see my points above.

There are 10 types of people: those who understand binary, and those who don't.

HogPilot is offline  
post #12 of 41 Old 09-28-2010, 01:06 PM
AVS Special Member
 
Vern Dias's Avatar
 
Join Date: Jun 1999
Location: Allen TX USA
Posts: 4,978
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Sounds like the lower resolution projector was chosen to mask the possible differences between the lenses. The lowest common denominator effect makes these tests suspect, at least in my eyes. Let's see these tests rerun with a 4K projector .

Vern
Vern Dias is offline  
post #13 of 41 Old 09-28-2010, 01:12 PM
Advanced Member
 
ilsiu's Avatar
 
Join Date: Jul 2004
Location: Minnesota
Posts: 867
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Vern Dias View Post

Sounds like the lower resolution projector was chosen to mask the possible differences between the lenses. The lowest common denominator effect makes these tests suspect, at least in my eyes. Let's see these tests rerun with a 4K projector .

Vern

I agree the results would be more relevant if a popular projector had been used (JVC, Epson, etc), but I still give a lot of credit to Annsi for laying out the ground work for a very thorough, controlled, and objective comparison. Bravo.
ilsiu is offline  
post #14 of 41 Old 09-28-2010, 01:24 PM
AVS Special Member
 
Oliver Klohs's Avatar
 
Join Date: Aug 2001
Location: Leipzig, Germany
Posts: 2,528
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Quote:
Originally Posted by HogPilot View Post

Maybe there's some underlying optical mechanism at work here that I don't understand?

Usually consumer projectors show decreased ANSI and increased on/off contrast with bigger throw ratios.

So changing the throw ratio from 1.8 to 2.4 would account for the difference in on/off measurements.

Regarding ANSI contrast the ultimate test would be a DLP with an ANSI contrast of more than 600:1 in a dark room - that would probably give results that give a better impression of what one loses with the anamorphic attachments.
Oliver Klohs is offline  
post #15 of 41 Old 09-28-2010, 01:29 PM
AVS Special Member
 
Gary Lightfoot's Avatar
 
Join Date: Jun 2000
Location: Surrey, UK
Posts: 4,451
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Liked: 38
Hi Anssi,

Thanks for going to the trouble of doing the testing.

When I measured the on/off CR through a Prismasonic H1000 lens a few years ago I found no change between having the lens in place or not. My room was pretty dark (black and dark grey) and with no ambient. The on/off of the pj I had at the time was 2707:1 IIRC, and that figure was the same with and without the lens. The lux measurement at the screen was 101 for the pj without the lens, and 99 with the H1000 in place and in pass through mode. So only a small amount of light loss (around 2% seems normal).

However, I don't understand how having no lens in place could have less on/off contrast than having a lens in the light path:

Quote:
Originally Posted by prismasonic View Post


Isco 3 (TR 2.4)
Contrast (ON/OFF): 944

--------------------------------

Pass mode, ISCO+SLED (TR 2.4)
Contrast (ON/OFF): 870

I assume the ISCO pass mode is the sled removing the lens from the light path?


Either the lenses are making the black blacker without affecting the white, or making the white brighter without affecting the black. Neither is likely but something seems to be changing somewhere. Just seems a bit odd. If a lens does change anything, being passive devices they should alter the black and white levels equally so the on/off should remain the same (I would expect the black and white levels to change equally as a percentage). You should see a small drop in ANSI CR with a lens in place though.

I did measure an ANSI contrast of around 400:1 with an ISCO lens in place in my room after covering around 80% of the screen with black velvet. That in effect cut down on a lot of reflected light and took a lot of the room effect out of the measurements. Before doing that I was getting a lot less (maybe 150:1 IIRC)

Gary

Quote:
Originally Posted by elmalloc
Who says Cameron is "right" and why do we care about him so much - lol!

I trust Gary Lightfoot more than James Cameron.
Gary Lightfoot is offline  
post #16 of 41 Old 09-28-2010, 01:37 PM
AVS Addicted Member
 
R Harkness's Avatar
 
Join Date: May 2001
Location: Toronto, Ontario, Canada
Posts: 11,912
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 49 Post(s)
Liked: 266
Quote:
Originally Posted by HogPilot View Post


These numbers don't seem to make sense, in that measured on/off CR actually went up with the lenses in place, and that the black floor dropped with the lenses in place - in both cases, more so with the HD5000R than the ISCO III!

Makes sense actually (as far as I know).

Most projector lenses have lower contrast the more you zoom the picture out. Using the zoom method to zoom out the image to fill the screen, contrast would decrease. Putting an A-lens in the path means you don't have to zoom the projector's lens out, preserving higher contrast from the projector.

(That's actually one of the things that keeps me intrigued by the thought of getting an A-lens).
R Harkness is online now  
post #17 of 41 Old 09-28-2010, 02:36 PM
AVS Special Member
 
Oliver Klohs's Avatar
 
Join Date: Aug 2001
Location: Leipzig, Germany
Posts: 2,528
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Quote:
Originally Posted by HogPilot View Post

4. You readily admitted that your room is already poorly suited for ANSI measurements, which are notoriously hard to accurately attain and reproduce. Things like the light, reflective walls in the room, coupled with the relatively poor optical quality of the business projector you used, don't lend themselves to accurate or useful ANSI measurements. As with the on/off CR measurements, there are plenty of HT owners who have rooms capable of much higher performance than the one you used to perform your measurements. Again, if we are to test these lenses at their limits, controlling all of these variables are important; illustrating that any lens of respectable quality is capable of upholding already poor ANSI CR performance isn't useful to those of us who have rooms and projectors capable of significantly higher performance. Would you agree with this?

The Isco 3 does reduce ANSI contrast only by a very small amount in my experience. So if the Prismasonic has an even higher measured value I would think that this indicates a very good ANSI contrast for the 5000M, too.

Still it would be interesting to compare these with a better projector.
Oliver Klohs is offline  
post #18 of 41 Old 09-28-2010, 04:01 PM
AVS Club Gold
 
HogPilot's Avatar
 
Join Date: Jun 2006
Location: Good Ol' US of A
Posts: 2,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Quote:
Originally Posted by ilsiu View Post

I agree the results would be more relevant if a popular projector had been used (JVC, Epson, etc), but I still give a lot of credit to Annsi for laying out the ground work for a very thorough, controlled, and objective comparison. Bravo.

I agree, I certainly wasn't trying to downplay what Anssi has done here, I applaud that he's willing to measure his product against what's considered a superior performer (granted, that costs several times more). However it seems that variables that could significantly affect the results weren't well accounted for - most notably the choice of a projector with relatively poor home theater performance in a less than suitable room.

Quote:
Originally Posted by Oliver Klohs View Post

Usually consumer projectors show decreased ANSI and increased on/off contrast with bigger throw ratios.

So changing the throw ratio from 1.8 to 2.4 would account for the difference in on/off measurements.

Absolutely - except the measurements I quoted/questioned above were ALL taken at a TR of 2.4, both with and without a lens in place. The only numbers attained at a TR of 1.8 were those for the zooming comparison, which I didn't really address.

Quote:
Originally Posted by Oliver Klohs View Post

Regarding ANSI contrast the ultimate test would be a DLP with an ANSI contrast of more than 600:1 in a dark room - that would probably give results that give a better impression of what one loses with the anamorphic attachments.

I completely agree that a much better DLP projector and a better suited room would yield more useful results given the capabilities of both Prismasonic's and ISCO's lenses.

Quote:
Originally Posted by R Harkness View Post

Makes sense actually (as far as I know).

Most projector lenses have lower contrast the more you zoom the picture out. Using the zoom method to zoom out the image to fill the screen, contrast would decrease. Putting an A-lens in the path means you don't have to zoom the projector's lens out, preserving higher contrast from the projector.

(That's actually one of the things that keeps me intrigued by the thought of getting an A-lens).

I understand what you're saying, but in this case Anssi took contrast measurements all at a TR of 2.4 with 1) no lens in place, 2) the ISCO III in place, and 3) the HD5000R in place. The contrast measurements went up with the lenses in place, which doesn't make sense since the projector wasn't moved, and the only way to increase contrast is to increase brightness or decrease black level. Both measurements show that the black level decreased by a significantly larger margin than did the max light output with the lens in place as opposed to no lens, which explains the increase in CR. This seems to indicate that the percentages of light a lens transmits and scatters is dependent upon the amount of light fed to it. In this case, both lenses scattered a greater percentage of light when they were fed lower intensities of light. I wouldn't think that the percentage of light lost through a lens should depend on the volume of light being fed to the lens, but I'm not an expert in optics so maybe there's something at work here that I don't understand. However the numbers don't seem jive on a "common sense" level.

Quote:
Originally Posted by Oliver Klohs View Post

The Isco 3 does reduce ANSI contrast only by a very small amount in my experience. So if the Prismasonic has an even higher measured value I would think that this indicates a very good ANSI contrast for the 5000M, too.

Still it would be interesting to compare these with a better projector.

I'm not saying that one is better than the other, only that the ANSI CR numbers presented here carry little to no weight because of the poor conditions under which they were measured.

There are 10 types of people: those who understand binary, and those who don't.

HogPilot is offline  
post #19 of 41 Old 09-28-2010, 10:37 PM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:


A couple questions about your test:

1. I am confused by your units "lux/m^2" - my understanding is that 1 lux = 1 lumen/m^2, which already takes area into account, so I'm not sure what your unit of lux/m^2 means. You later said that "Due to this the mean value of light meter result is yet multiplied by the active picture area." If you multiply lux by screen area, this gives you lumens - so are you saying your numbers are presented in lux or lumens? Did you mean to say lux * m^2 instead of lux/m^2?

Yes you are correct. It naturally should be lux * m^2.
I made correction to the report. Thanks!

Quote:


2. Why was the Panasonic PT-DW6300ES - a 1200x800 16:10 business projector with a 0.65" DLP chip - chosen as the test projector? Its poor contrast ratio (rated 2,000:1, measured less) isn't indicative of the much higher CRs available in home theater projectors, and thus doesn't allow you to test lens performance at the very low light levels that we are likely to experience in our home theaters. In addition, business projector optics are generally not nearly as high quality as those offered in even mid-priced home theater projectors - being that this is an optical test, I would expect that you'd want to use something better in terms of chip size/quality and optical properties. Having a quality imaging chip and projector optics are crucial when trying to compare the amount of CA and optical distortion introduced by an anamorphic lens, if we are to test them at their limits. In fact, the no-lens screen shot that you provide shows large amounts of red CA - almost one full pixel width on the left and about a half on top, which is much larger than either the ISCO III or the HD5000R will produce under these conditions! The ISCO III clearly reproduces the red fringe of CA seen in the no-lens picture, whereas the HD5000R shot shows no such fringe. If the screen shots are accurate reproductions of what the lenses are actually doing (i.e. none are out of focus or temporally blurred), this means that the ISCO is simply passing the projector's CA to the screen, whereas the HD5000R is introducing CA which happens to compensate for the projector's CA. Any thoughts on this?

The main reason for taking this projector to the test was that with this resolution you can better have a photo with a somehow visible pixel grid, so that the sharpness differences could be seen. Anyone who has taken screen shots (especially close ups) knows that it is not an easy task.

Also for me the projector is very clean from color fringing compared to the many other HT projectors. It is good to note that the camera also may add some CA. Generally, in my opinion the test shots shows pretty well what they should show -> sharpness and CA performance.

Quote:


3. Breaking down the numbers behind your on/off contrast measurements, I find the results odd. If I worked the math correctly (based on your throw ratio and distance), your 16:9 screen was 1.375 m X 0.77 m, giving it an area of 1.06 m^2. As I said before, multiplying measured lux by screen area yields lumen output of the projector - from here on out I'll work in lumens since it's a more common unit amongst FP users.

For no lens in place - the "reference measurement" - you measured 481.7 lumens at full brightness and 0.55 lumens at "full black" (rather abysmal black level performance), for an on/off CR of 870:1. With the ISCO III in place, you measured 472.1 lumens at full brightness (1.99% decrease from reference), and 0.50 lumens at "full black" (9.67% decrease from reference) for a CR of 944:1. With the HD5000R in place, you measured 454.1 lumens at full brightness (5.74% decrease from reference) and 0.47 lumens at "full black" (14.93% decrease from reference) for a CR of 964:1.

These numbers don't seem to make sense, in that measured on/off CR actually went up with the lenses in place, and that the black floor dropped with the lenses in place - in both cases, more so with the HD5000R than the ISCO III! Also, the ISCO "lost" almost 5x more light at full black than it did at full white; the HD5000R only "lost" about 2.6x more. Maybe there's some underlying optical mechanism at work here that I don't understand?

This what happened. Here are the measurement values in lux (for ratio they do not have to me multiplied with the area) Prismasonic get better value in lux compared to the ISCO because the front element decreases the picture a small amount.

isco 3 (TR 2.4): ON (mean): 321 lux - OFF (mean): 0.34 lux
HD5000R (TR 2.4): ON (mean): 328 lux - OFF (mean): 0.34 lux
Pass mode, ISCO+SLED (TR 2.4): ON (mean) :426 lux - OFF (mean): 0.49 lux

Now it is good to note that Isco and the Prismasonic results are well inside the margin of error, By increasing Prismasonic OFF (mean) value to 0.35 lux the contrast ratio would be already worse than with the Isco

Quote:


4. You readily admitted that your room is already poorly suited for ANSI measurements, which are notoriously hard to accurately attain and reproduce. Things like the light, reflective walls in the room, coupled with the relatively poor optical quality of the business projector you used, don't lend themselves to accurate or useful ANSI measurements. As with the on/off CR measurements, there are plenty of HT owners who have rooms capable of much higher performance than the one you used to perform your measurements. Again, if we are to test these lenses at their limits, controlling all of these variables are important; illustrating that any lens of respectable quality is capable of upholding already poor ANSI CR performance isn't useful to those of us who have rooms and projectors capable of significantly higher performance. Would you agree with this?

Overall it's clear that "bargain" lenses offer significantly poorer performance than more expensive lenses designed and treated to avoid CR and high levels of reflectance. However it seems that your tests aren't conclusive when looking at absolute performance levels of the ISCO III and HD5000R due to the issues I've pointed out above. It seems that you agree with this given your closing remarks, however a more in-depth discussion from you would certainly be welcome!

Yes I fully agree you. Especially with the ansi contrast measurements with a top performing projector, the room conditions should be very very ideal. The room walls and ceiling should be preferable covered by black velvet.

If someone has a good room and wants to arrange a test, I would be happy to borrow our lens to get along.

Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
post #20 of 41 Old 09-28-2010, 11:09 PM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Gary Lightfoot View Post


However, I don't understand how having no lens in place could have less on/off contrast than having a lens in the light path:

I assume the ISCO pass mode is the sled removing the lens from the light path?

I was thinking this too, and ended up to the following.
The lens zooms the picture (only to one direction, but anyway). This decreases the throw ratio, which makes the ON/OFF contrast better.

This may also be the answer to question 3 from HogPilot below

Quote:


These numbers don't seem to make sense, in that measured on/off CR actually went up with the lenses in place, and that the black floor dropped with the lenses in place - in both cases, more so with the HD5000R than the ISCO III! Also, the ISCO "lost" almost 5x more light at full black than it did at full white; the HD5000R only "lost" about 2.6x more. Maybe there's some underlying optical mechanism at work here that I don't understand?


Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
post #21 of 41 Old 09-29-2010, 03:42 AM
AVS Special Member
 
Highjinx's Avatar
 
Join Date: Dec 2002
Location: Australia
Posts: 1,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 23
When standing away from the monitor so as not to be able to 'see' the pixel structure, I find the zoomed image has more depth.

An A-Lens produced 2.35:1 images On/Off CR should be equal to the non optically stretched 16:9 image prior to optical stretching. The stretched image will be 33% less bright than the non stretched section.

The A-Lens produced image will have better on/offcontrast than a zoomed image of the same size, but less ANSI CR for reasons mentioned by Richard above.

The primary lens beam spot is smaller when using an A-Lens Vs Zooming, hence the findings that A-Lens On/Off Cr is better with an A-Lens Vs zooming for a same sized image.

May the success of a Nation be judged not by its collective wealth nor by its power, but by the contentment of its people.
Hiran J Wijeyesekera - 1985.
Highjinx is offline  
post #22 of 41 Old 09-29-2010, 03:50 AM
AVS Special Member
 
Highjinx's Avatar
 
Join Date: Dec 2002
Location: Australia
Posts: 1,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 23
The CR differences here are so small that the eye will not pick up the differences, '4x the difference to see a doubling/halving.

The important 'measurement' would be sharpness/detail loss and MTF differences when using an A-Lens and not.

May the success of a Nation be judged not by its collective wealth nor by its power, but by the contentment of its people.
Hiran J Wijeyesekera - 1985.
Highjinx is offline  
post #23 of 41 Old 09-29-2010, 03:54 AM
AVS Special Member
 
Oliver Klohs's Avatar
 
Join Date: Aug 2001
Location: Leipzig, Germany
Posts: 2,528
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Quote:
Originally Posted by HogPilot View Post

Absolutely - except the measurements I quoted/questioned above were ALL taken at a TR of 2.4, both with and without a lens in place. The only numbers attained at a TR of 1.8 were those for the zooming comparison, which I didn't really address.

Oh I missed that one of the measurements without the lens was made with a 2.4 throw ratio and you are of course right that this one value (870:1 on/off) at 2.4 TR is surprising.

Regarding the ANSI contrast comparison: I just wanted to point out that even with a more ideal environment the ISCO 3 loses little ANSI contrast (in the order of about 10% give or take a few) and that with the Prismasonic being on par with the ISCO here or a little bit better we could expect similar values from the Prismasonic lens.

But of course ideally we would want to start out at a much higher ANSI contrast to start with in order to verify this assumption.
Oliver Klohs is offline  
post #24 of 41 Old 09-29-2010, 05:28 AM
AVS Club Gold
 
HogPilot's Avatar
 
Join Date: Jun 2006
Location: Good Ol' US of A
Posts: 2,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Quote:
Originally Posted by prismasonic View Post

The main reason for taking this projector to the test was that with this resolution you can better have a photo with a somehow visible pixel grid, so that the sharpness differences could be seen. Anyone who has taken screen shots (especially close ups) knows that it is not an easy task.

Also for me the projector is very clean from color fringing compared to the many other HT projectors. It is good to note that the camera also may add some CA. Generally, in my opinion the test shots shows pretty well what they should show -> sharpness and CA performance.

I definitely understand how difficult it is to take screen shots - I've taken multiple shots of pixel grids up close on 1080p projectors, and you definitely have to have a camera that's up to the task. I have found that using a macro setting definitely helps, and as long as you get close enough the camera optics don't have to be superb in order to take a good screen shot. In fact, the closer you get, the less the camera optics matters as it will introduce much less CA than is induced by the projector and/or lens.

Just so I understand you, you said that the screen shots do accurately represent the amount of CA present in each scenario? If this is the case, I'd have to disagree that the projector is free of CA as there is a noticable amount of red pixel fringing on the top and left. If this is actually from the projector, you probably want to get a different projector. If this is due to the camera, then you might want to try to either get a closer shot or use a better quality camera - either way that much CA is far from acceptable for a single chip projector for home theater use.

Quote:
Originally Posted by prismasonic View Post

This what happened. Here are the measurement values in lux (for ratio they do not have to me multiplied with the area) Prismasonic get better value in lux compared to the ISCO because the front element decreases the picture a small amount.

isco 3 (TR 2.4): ON (mean): 321 lux - OFF (mean): 0.34 lux
HD5000R (TR 2.4): ON (mean): 328 lux - OFF (mean): 0.34 lux
Pass mode, ISCO+SLED (TR 2.4): ON (mean) :426 lux - OFF (mean): 0.49 lux

Now it is good to note that Isco and the Prismasonic results are well inside the margin of error, By increasing Prismasonic OFF (mean) value to 0.35 lux the contrast ratio would be already worse than with the Isco

Thanks for the raw data! It's good to see that I was wrong about the black floor changing, and it makes total sens that with a lens in the path that the light per unit area would decrease since you're increasing the image size by 33%. However the one thing that doesn't make sense is that, in the brightness test, you measured the ISCO as passing more light than the HD5000R at 100%, yet in this test it passed less than the HR5000R at 100%. This is definitely conflicting information. Why did you re-measure a max brightness for the CR test instead of just using the results from the original max brightness test? I understand that you're saying that the measurements are well within the margin of error, but we have two different tests with two different results here. Ultimately this leaves us with no useful results from either the max brightness test or the on/off CR test until we can get results for both that agree with each other.

Quote:
Originally Posted by prismasonic View Post

Yes I fully agree you. Especially with the ansi contrast measurements with a top performing projector, the room conditions should be very very ideal. The room walls and ceiling should be preferable covered by black velvet.

If someone has a good room and wants to arrange a test, I would be happy to borrow our lens to get along.

Anyone from Anssi's neck of the woods have a suitable room and want to step up? I would volunteer but I don't think he's willing to fly all the way to the US just for one test

There are 10 types of people: those who understand binary, and those who don't.

HogPilot is offline  
post #25 of 41 Old 09-29-2010, 05:51 AM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by HogPilot View Post

Why did you re-measure a max brightness for the CR test instead of just using the results from the original max brightness test? I understand that you're saying that the measurements are well within the margin of error, but we have two different tests with two different results here. Ultimately this leaves us with no useful results from either the max brightness test or the on/off CR test until we can get results for both that agree with each other.

I did not remeasure the max brightness. Prismasonic get better value in lux compared to the ISCO because the front element decreases the picture a small amount. When taking into account the area (lux*m^2), the brightness results are as informed (444 lm and 427 lm)

Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
post #26 of 41 Old 09-29-2010, 07:03 AM
Senior Member
 
alex_t's Avatar
 
Join Date: May 2006
Location: France
Posts: 297
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 19
Quote:
Originally Posted by HogPilot View Post


[...]
Anyone from Anssi's neck of the woods have a suitable room and want to step up? I would volunteer but I don't think he's willing to fly all the way to the US just for one test

I live in France near Paris. I own an ISCO II and I have an ISCO III L for few weeks.

I have a room completely dark and a screen in 2.37 format ( 3.6m x 1.52m) ! I'm looking for a 5000R to do some comparison .......

I'm french .... sorry for my english
alex_t is online now  
post #27 of 41 Old 09-29-2010, 09:25 PM - Thread Starter
Senior Member
 
prismasonic's Avatar
 
Join Date: Oct 2004
Location: Helsinki, Finland
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by HogPilot View Post

I definitely understand how difficult it is to take screen shots - I've taken multiple shots of pixel grids up close on 1080p projectors, and you definitely have to have a camera that's up to the task. I have found that using a macro setting definitely helps, and as long as you get close enough the camera optics don't have to be superb in order to take a good screen shot. In fact, the closer you get, the less the camera optics matters as it will introduce much less CA than is induced by the projector and/or lens.

I would be interested in seeing your shots as a reference. Could you please post them here. Thanks!


Quote:


I live in France near Paris. I own an ISCO II and I have an ISCO III L for few weeks.

I have a room completely dark and a screen in 2.37 format ( 3.6m x 1.52m) ! I'm looking for a 5000R to do some comparison .......

Thank you for your interest in this. However, unfortunately I already promised this to Oliver Klohs.

Anssi Leppanen

PRISMASONIC
www.prismasonic.com
prismasonic is offline  
post #28 of 41 Old 09-29-2010, 10:44 PM
Senior Member
 
alex_t's Avatar
 
Join Date: May 2006
Location: France
Posts: 297
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 19
Quote:
Originally Posted by prismasonic View Post


Thank you for your interest in this. However, unfortunately I already promised this to Oliver Klohs.

OK.

My throw ratio is 1.58 and I would like to reduce GEOMETRICAL DISTORTION.

My isco II gives good results. I think ISCO III L will be much better.

What about prismasonic 5000R ?

Regards

I'm french .... sorry for my english
alex_t is online now  
post #29 of 41 Old 09-30-2010, 02:14 AM
AVS Club Gold
 
HogPilot's Avatar
 
Join Date: Jun 2006
Location: Good Ol' US of A
Posts: 2,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Quote:
Originally Posted by prismasonic View Post

I would be interested in seeing your shots as a reference. Could you please post them here. Thanks!

From the "film-like" thread over in the $3K-plus projector forum:





These were photos of a Sim2 HT3000E (top) and BenQ W20K (bottom) taken to illustrate the difference that graded DMDs and optics can make in a projector image.

There are 10 types of people: those who understand binary, and those who don't.

HogPilot is offline  
post #30 of 41 Old 09-30-2010, 02:23 AM
AVS Club Gold
 
HogPilot's Avatar
 
Join Date: Jun 2006
Location: Good Ol' US of A
Posts: 2,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Quote:
Originally Posted by prismasonic View Post

I did not remeasure the max brightness. Prismasonic get better value in lux compared to the ISCO because the front element decreases the picture a small amount. When taking into account the area (lux*m^2), the brightness results are as informed (444 lm and 427 lm)

Ah, so the HD5000R is actually shrinking the image as compared to the ISCO III? By how much is it doing this?

With a smaller image but similar black levels in lux, that means that either 1) the HD5000R is scattering some light so that the black level reads the same as with the ISCO III in place (which would require a re-calibration), or 2) the light meter was at it's 0.01 lux threshold and and not registering the difference between the two black levels. Either way it definitely seems that this bears more investigating.

There are 10 types of people: those who understand binary, and those who don't.

HogPilot is offline  
Reply 2.35:1 Constant Image Height Chat

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off