Hi all,
So I took delivery of 2 trophy prisms from Crystal Factory a couple of weeks ago. I took the ptae1000u off the ceiling and set it up on a table the same distance as my ceiling mount and projected it on my 2.37 BOC screen. I put the prisms in front of the lens and fooled with it for about an hour or so. It really was quite a simple process to get the stretch correct.

The problem was the focus. In pass-through mode, the focus was crystal clear, but when the wedges get aligned to stretch the image, everything goes blurry. Nothing I did with the wedges or focusing the projector could bring the image into focus.

Granted the 1000u is not the sharpest image to start with, but at my seating distance (12ft, same as my throw) there has never been an issue with the smoothscreen causing an unfocused image.

Am I just seeing an accentuated smoothscreen focus issue, due to the stretch or am I missing something here. Anyone else experience anything like this?

My screen is 36"x85" with a throw of 12' if these specs will help with a solution.

Thanks,

Darryl

A couple of things to consider -

These prisms are trophies and were never intended to be used as a optical component. Granted they are smooth and appear flawless to the eye and may even be finished to a "comercial optical grade", but they are far from the true optical correctness needed for a lens.

Your projector's smoothscreen is by default a softening filter, and the displaced prisms only add to that effect.

If your pixels start out as 1 x 1 mm squares, they become 1.33 x 1mm after the anamorphic stretch. The problem with a 2 prisms lens goes beyond that in that the prisms tend to keep stretching the light beyond the desired 1.33x. Your pixel could be as wide as 1.5 x 1 at the very edges.

Without a correction element, there is nothing you can do short of reducing the amout of stretch which then means you do not have geometric correct images in the centre of the screen...

Mark

Thanks for your reply Mark.
I didn't expect perfection from these prisms, but I dont hear anyone talking about major focus shifts when using them, so I thought I was doing something wrong.

It is likely as you say, the stretch is accentuating the smoothscreen. When trying to focus a stretched image I can get vertical lines (on a focus chart) close, but any horizontal lines are brutal. When I focus to a point where the horizontal line are acceptable, the vertical lines are awful.

If it was purely the poor quality of the prisms though, I dont think I would be able to focus it as well as I can in pass-through alignment. Focus in this alignment appears as if there are no prisms between the projector and the screen.

I have a cheap lcd projector at work where the screen door effect is seen at its best, maybe I will bring the prisms in and do a test stretch to see if the focus is affected as well.

Thanks again,

Darryl

Thanks for your reply Mark.
I didn't expect perfection from these prisms, but I dont hear anyone talking about major focus shifts when using them, so I thought I was doing something wrong.

The concept works and it is quite an experience to project Scope the way it was meant to be seen, but the truth is, it is far from perfect. Many, including myself have been living in dream if we think this is optimal...

When trying to focus a stretched image I can get vertical lines (on a focus chart) close, but any horizontal lines are brutal. When I focus to a point where the horizontal line are acceptable, the vertical lines are awful.And, dare I say, is about the best you can do with out adding addional elements...

If it was purely the poor quality of the prisms though, I dont think I would be able to focus it as well as I can in pass-through alignment. Focus in this alignment appears as if there are no prisms between the projector and the screen.In pass mode, you have two parrallel faces, so in essence, the light passes right through unaltered. Non coated prisms may or may not add a slight reflection or reflect light away from the screen...

I have a cheap lcd projector at work where the screen door effect is seen at its best, maybe I will bring the prisms in and do a test stretch to see if the focus is affected as well.It will be an interesting test for sure, but I am guessing you will see the same thing there too.

Not to sound negative, but there is way more to good optics...

Mark

Not to sound negative, but there is way more to good optics...


Agreed. But even back in the day when you guys first discovered these prisms, I never read anything that would make me pause because of comments about debilitating focus.

I guess I will test on the cheap lcd, just for kicks, but the reality is I have a decision to make. Live with the poor focus (in live action, it isnt as noticable as on the focus chart) or go back to zooming.

Thanks for your help Mark

Darryl

I guess I will test on the cheap lcd, just for kicks, but the reality is I have a decision to make. Live with the poor focus (in live action, it isnt as noticable as on the focus chart) or go back to zooming.

Thanks for your help Mark

Darryl

Not a hard one though Darryl. Use the full panel or throw away 25% of the vertical rez? I'll take the softened image thanks ;)

Mark

Thanks for your reply Mark.
I didn't expect perfection from these prisms, but I dont hear anyone talking about major focus shifts when using them, so I thought I was doing something wrong.

It is likely as you say, the stretch is accentuating the smoothscreen. When trying to focus a stretched image I can get vertical lines (on a focus chart) close, but any horizontal lines are brutal. When I focus to a point where the horizontal line are acceptable, the vertical lines are awful.

If it was purely the poor quality of the prisms though, I dont think I would be able to focus it as well as I can in pass-through alignment. Focus in this alignment appears as if there are no prisms between the projector and the screen.
I´ve used a commercial anamorphic lens for over a year now. When I changed my 720p projector for the Panasonic AE2000 which I have now I noticed this same flaw in my setup that you mentioned earlier. Seems like this problem occurs whether its a DIY or commercial lens. 1,78:1 is very sharp but 2,35:1 is not. I remember noticing it also with the older projector but it was then my first projector and I didn´t have the hearth (or experience) to admit to myself that my expensive lens made Cinemascope soft. I surely notice the out of focus thing with 2,35:1 now that my Panasonic has a focusing picture and produces a razor sharp image in 16:9. Sadly I notice this also with movies. It bugs me and I´m going to have to add a front element to in front of the lens. If I buy one from Prismasonic it´s going to cost me hundreds of euros. :mad: This cost is something that I feel I shouln´t have to spend on a lens that cost me almost 2000 euros.

I don´t believe that people haven´t noticed this big of a flaw in their own picture and I don´t understand why there hasn´t been more widespread talk of this.

I´ve used a commercial anamorphic lens for over a year now. When I changed my 720p projector for the Panasonic AE2000 which I have now I noticed this same flaw in my setup that you mentioned earlier. Seems like this problem occurs whether its a DIY or commercial lens. 1,78:1 is very sharp but 2,35:1 is not. I remember noticing it also with the older projector but it was then my first projector and I didn´t have the hearth (or experience) to admit to myself that my expensive lens made Cinemascope soft. I surely notice the out of focus thing with 2,35:1 now that my Panasonic has a focusing picture and produces a razor sharp image in 16:9. Sadly I notice this also with movies. It bugs me and I´m going to have to add a front element to in front of the lens. If I buy one from Prismasonic it´s going to cost me hundreds of euros. :mad: This cost is something that I feel I shouln´t have to spend on a lens that cost me almost 2000 euros.

I don´t believe that people haven´t noticed this big of a flaw in their own picture and I don´t understand why there hasn´t been more widespread talk of this.

Well there are quite a few of us out here who have not bought into the anamorphic lens hype for the very reason that you have stated. The simple fact is that sticking any A-lens in front of your projector is going to produce some softening of focus and some loss of contrast, as well as pin cushion distortion. The A-lens crowd don't want to hear this because they have sold themselves the idea that using the full panel height of the projector actually enhances the 2.35 image. But that advantage is more than offset by the optical problems induced by the A-lens. The fact is, If you want the sharpest possible image across the full 2.35 screen you stay with zooming, which introduces none of the A-lens artifacts. The only selling point for the A-lens, in my opinion, is convenience - it is sometimes logistically simpler to slide in an A-lens than do a zooming and lens shift operation, and there may be a 15% brightness advantage in using a lens. But even that advantage is disappearing with the latest projectors now providing remote zooming and shift capability, and stacks of reserve brightness.

Some rooms may not be long enough to get the width you need unless an anamorphic lens is used.

And not all projectors have the zoom requirements either, so an anamorphic lens is the only way to go in these cases for Scope...

Mark

taffman

I´m sure you are right with zooming being the way to go for the sharpest possible picture. Unfortunately it doesn´t seem to be the best in all the other ways.

I look for the best in both picture and convenience and because of that I don´t want to throw away my A-lens. I think that brightness is about as important as sharpness. My Panasonic can´t light 110" of 2,35:1 SmX-screen the way I want it to without the lens. I also want the biggest picture area with 2,35:1 not 1,78:1. This is because my eyes are beside each other horizontally not vertically. I can´t watch an overly tall picture because it just doesn´t fit in my view. I want to always watch as BIG a picture as I can comfortably and that makes me want to keep the height the biggest I want in all the movies and change only the picture width. So I need to keep the height constant and I can accomplish that with the lens but not with zooming.

Because of using a curved screen I have virtually no pincushion distortion. My image is sharp with 1,78:1. I can change aspect ratios with a push of a button. The over all picture is very good. Soft focus for 2,35:1 is the only issue I have with this setup. I have gotten the impression that a frontal element like the one that Prismasonic sells will solve this problem. If it does then great. I will be completely happy with the PQ. Still I´m pretty amazed that this issue didn´t come up while reading AVS (or other home theater sites) before buying the lens. Also I would like to solve this flaw with only a few dollars not many hundreds` of dollars

I think it all depends on your particular equipment and room set up. For my particular set up I have a shelf mounted Panny at the rear of the room. Changing to 2.35 with constant image height involves 1) zooming out the picture to the full width of the 2.35 screen 2) electronically raising the vertical position of the picture to center it on the 2.35 screen. This operation takes me less than 30 seconds, and is usually accomplished by the time the films studio logo has faded out. There is no focus adjustment required.
If you have a ceiling mounted projector which does not have the 2 X zoom range and remote picture centering feature, that the Panny's have, then I can certainly appreciate that a sliding anamorphic lens is more convenient, but let us not say that it is necessarily better in terms of picture quality. For myself, I would much more accept a slightly less bright picture (with zooming)than one with a softer focus (with A-lens). We are only talking about a 15% increase in brightness with the A-lens compared with zooming, so the brightness isue is really not a big deal and can easily be solved by switching the prohectors lamp from the LOW LAMP mode to NORMAL.
Your particular posts on this issue have been very honest - you clearly see a degradation in picture focus using your A-lens, even though you still like its convenience, which is fine. I just wish other A-lens users would be as honest, and quit propogating the misconception that A-lenses boost picture quality compared with simple zooming.

I understand and respect the reasons why you have chosen the Way of the Zooming Cinemasope. I´ll probably try it out also when I take out my A-lens for the front-element install. :D Seriously. I don´t want to compromise with brightness because that was the main reason that made me want to give the previous Sony projector away. I don´t feel that my AE-2000 has left over brightness for zooming in it´s best mode (colour1) even though I don´t have it in low mode. But. If the front element doesn´t make Cinemascope sharp I´m going to have to lower my opinion of (at least some) anamorphic lenses.

Ok, so what can we do to add a correction element to these prism based lenses? :confused:
I know Mark did come up with "CAVX Corrector" with pretty excellent results, but is not pursuing it anymore??? :confused:
There has to be a DIY path to put this focusing issue behind us once and for all :)

Come on Mark!, please tell us what we can use to get this focusing issue resolved :D

What can I say except that there is no CHEAP solution here, and why I have not continued the project. The type of lens you need has to be manufactured by a lens company...

Mark

I'm really glad this thread was revived after the database crash. This is the type of thread I was looking for before I purchased my prisms. I too will be zooming, as the PQ degredation far outweighs the drop in brightness, according to myself and everyone I have done the demonstration to. Thanks to all for your candid and honest statement.

Darryl

Test patterns absolutely show the softening of the image and focus problems. I have tended not to notice that much when I am watching a movie, however. Fact is, we don't sit and watch test patterns for two hours.

But this is not to say that one is wrong to reject the lens because of these issues - especially in pursuit of perfection.

DIY stands for Do It Yourself and should not always be assumed as low cost...

Mark

An interesting discussion. What could be the reasons for the soft focus issue of the DIY lenses. Is it the less than perfect glass surface ot prism material? Is it related to engineering precision or the fundamental design? Have any of you seen similar issues with main brands?

I think you find that ALL 2 prisms lenses suffer from this...

Mark

I think you find that ALL 2 prisms lenses suffer from this...

Mark

Does that mean this focus issue relates to the two prism optical design rather than the material precision etc?

Does that mean this focus issue relates to the two prism optical design rather than the material precision etc?

I can't comment on other 2 prisms lenses on the market, but the Aussiemorphic Lens used BK7 glass prisms finished to a commercial optical grade. The design had no correction for CA, grid distortion or astigmatism, so yes I would say the limits of the design, not the materials used...

Mark

I think you find that ALL 2 prisms lenses suffer from this...

Mark
This would be my assumption also.

Thanks guys.

Does the focus issue relates mainly to astigmatism of 2 prism design. Are there other factors that contribute to the focus issue? So, I expect, an optically corrected design for astigmatism (e.g. expensive brands), should totally eliminate the soft focus issue.

Thanks guys.

Does the focus issue relates mainly to astigmatism of 2 prism design. Are there other factors that contribute to the focus issue? So, I expect, an optically corrected design for astigmatism (e.g. expensive brands), should totally eliminate the soft focus issue.

I have seen some very expensive and cpmplex lenses and the common point they all have is correction elements for CA, GD, Astigmatism. I don't think you can truly correct Astigmatism with a prism lens simply because the prisms faces are flat, therefore they have no focal length and are not focal distance dependant...

Mark

Just want to throw something out there if my math is right... it is actually a gain of more then 24% in brightness as opposed to 15% that taffman has indicated... I think. :)

Full panel 1920 x 1080 = 2,073,000 pixels
If 1920 / 1.78 = 1078
then
1920 / 2.35 = 817
then
1920 x 817 = 1,568,640 pixels
Leaving the difference between them
2,073,000 - 1,568,640 = 504,360 pixels
For a loss of 24.3% of pixels
Pixels = Light

Is that right? I lack confidence in this, though I know I've posted it more then once.

Now does a 24% gain in brightness mean more to you then 15%? I don't know, I'm still zooming because I'm too lazy to build something to put my prisms on :)

All lenses that just comprise 2 prisms will suffer from differential focus between the horizontal and vertical planes. It's inevitable and - at HT throws and throw ratios - can never be fixed by twiddling the angles betwwen prisms, or making them fatter or skinnier. There is no secret forula. It just won't work.

In other words, if you have a test pattern comprising horizontal lines and verticals lines, you can get either focused, but not both at the same time.

The longer the throw ratio and the longer the absolute throw, the less this difference is and hence the best focus you get. Long throws and large throw ratios are typical of commercial cinemas. This is why Panavision was so successful witht heir initial product: a two-prism (color-corrected) system. But even they had to offer corrector lenses for "short" throws. Panavision's definition of "short"? 70 feet and under!

A corrector lens is a very weak cylindrical lens (say outside radius of curvature 1000mm, inside radius of curvature 998mm) which pre- or post-astigmatises the beam (depending on whether it's before or after the prisms in the beam) in the opposite direction to that which the prisms astigmatise the beam. The astigmatism factors - one positive, one negative - then cancel each other out.

However, this only works for fixed throws. Change the throw, and you have to change the focus correction required.

However, the loss of focus is not knife-edged (i.e. it doesn't fall off the instant you change throw by even a millimetre) so you have a bit of tolerance back and forth in your throw before you need a new corrector lens. Which is why Panamorph offer a series of correctors, each one pre-set for a certain throw distance range. I'm surprised Prismasonic don't offer this option too.

Consider a piece of plate glass or Lexan and (assuming it's flat and without lumps) imagine warping it just short of the shattering point.

If the glass or Lexan is 5mm thick, any bending will force the inside radius of curvature to be 5mm less than the outside radius of curvature. The trick is to be able to bend the glass or Lexan to the extent that the 5mm difference in radii of curvatures, as well as the absolute curvatures themselves, is also what is needed to de-astigmatize the image on screen.

Say for example you could bend the glass/Lexan so that the outside radius of curvature was 1000mm. The inside radius would be 995mm (assuming the plate is 5mm thick). If the 1000mm/995mm radii are what's needed to correct astigmatism then you've got a somewhat corrected prism system. I say "somewhat" because this technique is ultimately just a "suck it and see" process..

A whole bunch of caveats follow:

1. It will be hard to bend your pane of glass or Lexan into a symmetrical curve. Be prepared for the focus on one side to be different than the other side.

2. Do not confuse a blurred image due to color aberration with a blurred image due to astigmatism (they can look the same with fine detail). Use a coarse test pattern, not a fine one.

3. You might have to bend the glass past the shatter point. In which case your project is doomed from the start. Or else you can use Lexan, which is more malleable, but may distort or "craze" during bending.

4. Correction will be an improvement on what you had before, but never as good as a properly ground glass corrector lens with precise radii. This is because warping a flat pane of glass/Lexan into a curved pane of glass/Lexan is really just a sort of trick, in that the optics of the system will see this a almost the same as just the original flat pane of glass/Lexan. The reason it sort-of works is contained in the word "almost" (in the previous sentence).

5. This does nothing at all to correct for color aberration or grid distortion.

6. I think Panamorph have a patent on this process (they've patented just about everything else to do with prism lenses).

7. You WILL drive yourself crazy trying this, so don't blame me when your wife has you committed to the Funny Farm.

8. Wear leather protective gloves to prevent lacerations from broken glass, if glass is used, or else she'll know you went mad... why else would you slash your wrists?

9. Each system will be different, so please don't ask me for any more details. This is a DIY Forum, right? So DIY away. I offer no guarantees of success, as there are too many variables out there to do so.

Just want to throw something out there if my math is right... it is actually a gain of more then 24% in brightness as opposed to 15% that taffman has indicated... I think. :)

Full panel 1920 x 1080 = 2,073,000 pixels
If 1920 / 1.78 = 1078
then
1920 / 2.35 = 817
then
1920 x 817 = 1,568,640 pixels
Leaving the difference between them
2,073,000 - 1,568,640 = 504,360 pixels
For a loss of 24.3% of pixels
Pixels = Light

Is that right? I lack confidence in this, though I know I've posted it more then once.

Now does a 24% gain in brightness mean more to you then 15%? I don't know, I'm still zooming because I'm too lazy to build something to put my prisms on :)

Your calculations are correct, but they do not take into account the change in relative aperture (F number) of the projector lens when you use the zooming method and zoom out to a larger 2.35 picture. As you zoom out the projector lens for a 2.35 screen, the f number of the lens decreases and you are letting more light out of the projector. The amount depends on the set up but a 10% gain is a typical figure. So the 24% advantage of using an A-lens is reduced in practice ,by about 10%, to about 14%. So most people are not going to see any significant difference in brightness between the two methods

So most people are not going to see any significant difference in brightness between the two methods
I didn't do it for brightness, but rather being able to use the FULL vertical rez, not sacrifice 25%...

Mark

Your calculations are correct, but they do not take into account the change in relative aperture (F number) of the projector lens when you use the zooming method and zoom out to a larger 2.35 picture. As you zoom out the projector lens for a 2.35 screen, the f number of the lens decreases and you are letting more light out of the projector. The amount depends on the set up but a 10% gain is a typical figure. So the 24% advantage of using an A-lens is reduced in practice ,by about 10%, to about 14%. So most people are not going to see any significant difference in brightness between the two methods

I learn more from this site every day... honest :) Thanks!

I'm glad it was you who explained that this time, Taffman.

But saying "you are letting more light out of the projector" might get people thinking the image is brighter the more it is zoomed out. I've seen this misconception a few times here.

So, just a quibble, it's probably better to say that, when you zoom out, more light from each pixel reaches the projector lens optics because of the lower F number at the wider zoom. So, for a wider zoom, the larger (but inevitably dimmer) image just doesn't get quite as dim as you'd think it would on a screen size comparison alone.

I'm glad it was you who explained that this time, Taffman.

But saying "you are letting more light out of the projector" might get people thinking the image is brighter the more it is zoomed out. I've seen this misconception a few times here.

So, just a quibble, it's probably better to say that, when you zoom out, more light from each pixel reaches the projector lens optics because of the lower F number at the wider zoom. So, for a wider zoom, the larger (but inevitably dimmer) image just doesn't get quite as dim as you'd think it would on a screen size comparison alone.

Right on Aussie Bob, there is no way of getting around that inverse square law!
This is why statements like " you get a brighter picture with an anamorphic lens" are so confusing and misleading. All things being equal, a CIH scope image (using the whole projector panel by vertical stretching) is theoretically going to be only about half as bright (58% to be exaact) as a 16:9 picture of the same height. And thats not taking into account the light absorption of the A-lens, probably a few more percent. On the other hand , a zoomed up letterboxed 2.35 image will be 35% as bright as a 16:9 picture of the same height, but because of the F number decrease as you zoom out the lens, you will pick up an additional 10-15% in screen brightness. This gives a zoomed 2.35 image about 45-49% the brightness of the 16:9 image of the same height.
Less bright than the A-lens method for sure, but not by a whole lot, and nothing that cannot be overcome by switching the lamp to the higher brightness mode.
Bottom line, a 2.35 scope image in a CIH set up is always going to be much much less bright than your 16:9 and 4:3 image, no matter what you do. There is simply no way around this.

And your evidence to support this in a real world application is?

Mark

Don't agree with you there, Taffy.

You seem to be assuming that the image expansion of an anamorphic lens is 4/3 in both directions. If this was the case then the brightness of the expanded image would be 3/4 x 3/4 = 9/16 = 56.25%.

However, this is not the case. The expansion is in one direction only, so the formula is 1 x 3/4 = 3/4 = 75%. Multiply by 0.95 to account for an (average) 5% light loss through the lens and the final figure is 0.95 x 0.75 = 71.25% of the brightness of the original 16x9 image, not the (roughly) 58% less 5% or so (for light loss through the lens) you claim.

Alternatively, looking at the "zoom method" scenario, your 58% formula is roughly correct (it's actually 56.25%), as the image is expanded in both horizontal and vertical directions... it is a straight zoom out to a larger size.

However, a simple application of the Inverse Square Rule does not apply. As the image is zoomed out the aperture of the projector becomes more efficient. This is because, effectively, the "hole" that forms the aperture is moved closer to the imaging chip, thus allowing the gathering of more light rays bounced off (in the case of DLP systems) or transmitted through (in the case of LCD systems) the imaging chip.

Why does this happen?

Think of standing outside a window with a candle in your hand. If you stand 10 feet away from the window, only a small amount of the light from the candle will get through the window (the rest will disappear into the night sky). Now move closer, to 3 feet. Much more of the light from the candle will now reach and pass through the window. The "window" in this case is analogous to the "aperture" of the projection lens. As a projection lens is zoomed (i.e. the lens's focal length is reduced) the effective distance of the lens to the imaging chip decreases, in a similar way to our friend with the candle moving closer to the window. Hence, more light from the imaging chip enters the projection lens optics, increasing the lens's light transmission efficiency.

(The complex optical systems of projectors are not as simple as in my "candle and window" illustration above, but the general principle I described applies, to greater or lesser extents, to all projection systems)

The end result of all this is that the application of the Inverse Square Rule is somewhat reduced by the greater efficiency of the projection lens at wider zooms. This extra efficiency must be compounded with the 56.25% figure derived from the Inverse Square Rule: the increase in efficiency is multiplied by the decrease in brightness to give an overall higher final brightness figure than you'd expect at first glance.

Let's say the projection lens becomes 12% more efficient at passing light with a 4/3 zoom applied to it. This would increase our 56.25% to 56.25 x 1.12 = 63.0%. Now, divide the anamorphic lens figure of 71.25% by the 63.0% figure and the result is 113.1%.

The anamorphic lens screen brightness, in this scenario, is 13.1% brighter than the zoom method. This percentage varies depending on projector optics, zoom positions (start and finish) used with the zoom method, screen gain and the transmissive qualities of the anamorphic lens.

So (sorry to contradict, Taffy) you do generally get a brighter image with an anamorphic lens, compared to the "zoom method". In my personal case (an AX-100, 120" 'scope screen, at a TR of 2.1, with an anamorphic lens of my own design) the figure is slightly less than 20%.

You are correct in saying that switching on the "high gain" function of the lamp system while using the "zoom method" would overcome the brightness difference between anamorphic lens and "zoom method" techniques. But what's good for the goose is good for the gander: doing the same thing with ananamorphic lens in place would stretch the brightness gap out again.

Just want to throw something out there if my math is right... it is actually a gain of more then 24% in brightness as opposed to 15% that taffman has indicated... I think. :)

Full panel 1920 x 1080 = 2,073,000 pixels
If 1920 / 1.78 = 1078
then
1920 / 2.35 = 817
then
1920 x 817 = 1,568,640 pixels
Leaving the difference between them
2,073,000 - 1,568,640 = 504,360 pixels
For a loss of 24.3% of pixels
Pixels = Light

Is that right? I lack confidence in this, though I know I've posted it more then once.

Now does a 24% gain in brightness mean more to you then 15%? I don't know, I'm still zooming because I'm too lazy to build something to put my prisms on :)

Prior to compensating for the impact of the zooming mechanism, your gain is about 33% not 25%. The pixel loss is about 25% - correct. But you need a reverse calculation to workout the gain. For example, 25% reduction of 100 is 75. And about 33% increase of 75 is 100.

So the zoom impact, say 10%, should be removed from 33%. So the net light gain is about 23% and it is not insignificant.:) This is correct assuming the final size (area) of the picture of the zoom method and the lens method is the same.

Don't forget to subtract a further (about) 5% for light loss through the lens.

So, the light gain would be about 20% due to an anamorphic lens unless projector position is changed to compensate for the light loss due to the change in zooming ratio. (I have read somewhere that the light loss of UH480 is about 3%).

Thanks Aussie Bob, I can see that my calculation was screwed up, and the correct number is indeed about a 13% brightness advantage of the A-lens method over the zooming method. Not really a huge difference, and the trade off between the two methods is probably not so much brightness but other factors, such as convenience of the A-lens method versus the possibly sharper field focus and better contrast of the zoom method.
Of course the new Panasonic PT-AE3000, with programmable focus,zoom, and vertical position memory, is going to totally eliminate the convenience advantage of the A-lens, so then the choice really will all come down to the relative picture quality of the two methods. And I have yet to see a convincing conclusion on that question.

Of course the new Panasonic PT-AE3000, with programmable focus,zoom, and vertical position memory, is going to totally eliminate the convenience advantage of the A-lens, so then the choice really will all come down to the relative picture quality of the two methods. And I have yet to see a convincing conclusion on that question.

Nothing like placing all your eggs in one basket...

Mark

In case of an anamorphic lens, there is a perceivable resolution increase. The impact of res increase due to anamorphic stretch cannot be fully discounted just saying that the resolution was not there to start with. The original resolution of 2.35:1 picture is about 1920x810. The lens method will not increase this to 1920x1080, however, there would be a perceivable resolution increase - the end result would be some where between 1920x810 and 1920x1080 depending on the quality (extrapolation capability) of the scaler.

If this is not the case, DVDs will not benefit from the upscaling DVD players - but the perception is indeed there is a benefit in upscaling DVDs. The same applies to the anamorphic upscaling which would increase perceivable resolution of the original 2.35:1 image.

In case of an anamorphic lens, there is a perceivable resolution increase. The impact of res increase due to anamorphic stretch cannot be fully discounted just saying that the resolution was not there to start with. The original resolution of 2.35:1 picture is about 1920x810. The lens method will not increase this to 1920x1080, however, there would be a perceivable resolution increase - the end result would be some where between 1920x810 and 1920x1080 depending on the quality (extrapolation capability) of the scaler.

If this is not the case, DVDs will not benefit from the upscaling DVD players - but the perception is indeed there is a benefit in upscaling DVDs. The same applies to the anamorphic upscaling which would increase perceivable resolution of the original 2.35:1 image.

I think that whether or not upscaling improves the image depends on the image content. Images with low frequency spatial detail will look better with upscaling due to reduced 'jagginess' while high spatial frequency images may be susceptible to softening/moire artifacts, resulting in loss of detail.

For DVD, everything is low frequency compared to 1080p/720p, so pretty much always looks better upscaled.

I think that whether or not upscaling improves the image depends on the image content. Images with low frequency spatial detail will look better with upscaling due to reduced 'jagginess' while high spatial frequency images may be susceptible to softening/moire artifacts, resulting in loss of detail.

For DVD, everything is low frequency compared to 1080p/720p, so pretty much always looks better upscaled.

Okay. Good point. Who to decide the low frequency range, the high frequency range; and the cutoff points. Since this is a perception related matter, human factors scientific experiments are needed to determine the impact of frequency spatial details to perceptions. Do we have the results of any such controlled scientific experiments?

Okay. Good point. Who to decide the low frequency range, the high frequency range; and the cutoff points. Since this is a perception related matter, human factors scientific experiments are needed to determine the impact of frequency spatial details to perceptions. Do we have the results of any such controlled scientific experiments?

Good question. It seems like a straighforward experiment: show a bunch of people a bunch of single frequency test patterns and get their opinions at which frequency things start to look weird.

Should be simple (for someone else to do, not me :))

But to be serious, my interest is only academic. I'm not picky enough to care about upscaling artifacts. Price and ease of use are more important factors to me.

Just a thought...The original DIY lenses that moved to DIY Audio were VC. They progressed to HE after a few years. So, if these single frequency lines are vertical, then with a VC (even a DIY lens), there should be no change across the horizontal, but may exhibit some shift in the vertical...

Mark