What is the reason to do 2.35:1 constant height - Page 7 - AVS Forum
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post #181 of 208 Old 04-28-2009, 03:27 PM
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Can't watch it now. Too boring for words.

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post #182 of 208 Old 04-28-2009, 05:26 PM
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Coldmachine, you seem to have a habit of editing your posts long afer you originally wrote them and it makes it really hard to keep track. Just to be clear, you are now saying it's just the new installs that are virtually all 2.40:1 ish constant height? I didn't get that from your orginal post which is why I posted the lists. I know Keith said that when they re-did their screening room they deliberately went for constant width for quality reasons but beyond that I don't have any data on new installs. The thing that puzzels me is why wouldn't they (screening rooms) just go for a screen (with variable masking) that fills the wall like they have always done (custom ratio)? The only thing that has changed is more digital and with DCI you don't need to use anamorphic lenses to display the film. Anyway you are right, time to move on.

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post #183 of 208 Old 04-28-2009, 05:27 PM
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Originally Posted by LilGator View Post

CAVX, you keep saying that, but making up data in a scaler doesn't make the source 1080 lines of vertical resolution all of the sudden. It's just convenient for your lens setup.

No but it uses the full resolution of the panel (both vertically and horizontally) this shows up as a significantly less coarse looking image. I've gone back and forth here using both techniques and it is no contest.

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post #184 of 208 Old 04-28-2009, 05:38 PM
 
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Originally Posted by Art Sonneborn View Post

No but it uses the full resolution of the panel (both vertically and horizontally) this shows up as a significantly less coarse looking image. I've gone back and forth here using both techniques and it is no contest.

Art

Only for exactly 2.37 material, Art. 2.35 gets cropped in the stretch (817 vertical pixels X 1.333... = 1089.33 with only 1080 being available) and anything less than 2.35 does not use full horizontal resolution when the lens is kept in place. Anything greater than 2.35 doesn't use full vertical resolution (2.40 is only 1067 pixels when vstretched).

By the way, the largest thread in this sub-forum debates lens vs. zooming, so it's far from a decided conclusion. Both have their advantages.
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post #185 of 208 Old 04-28-2009, 05:48 PM
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Originally Posted by LilGator View Post

Only for exactly 2.37 material, Art. 2.35 gets cropped in the stretch and anything less than 2.35 does not use full horizontal resolution when the lens is kept in place. Anything greater than 2.35 doesn't use full vertical resolution.

Oh my god ,you are comparing that to the massive jettisoning of pixels you get with zooming ! I hope you aren't going there with a straight face.

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post #186 of 208 Old 04-28-2009, 05:54 PM
 
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Originally Posted by Art Sonneborn View Post

Oh my god ,you are comparing that to the massive jettisoning of pixels you get with zooming ! I hope you aren't going there with a straight face.

Art

You really want to go there in this thread? You are "jettisoning" exactly...

ZERO

... pixels from the source by zooming.

You have to take into account scaling artifacts, a second lens the image has to pass through, contrast loss... before you can say zooming is inferior.

With the most expensive video processors and lenses the advantage may be there; projector scaling and budget lenses ... it may not.

I don't see the relevance to a CIH vs CIA debate though.
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post #187 of 208 Old 04-28-2009, 05:58 PM
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Originally Posted by LilGator View Post

You really want to go there in this thread? You are "jettisoning" exactly...

ZERO

... pixels from the source by zooming.

You have to take into account scaling artifacts, a second lens the image has to pass through, contrast loss... before you can say zooming is inferior.

With the most expensive video processors and lenses the advantage may be there; projector scaling and budget lenses ... it may not.

I don't see the relevance to a CIH vs CIA debate though.

I'll go there any time ,at least I've looked at it head to head on a very high quality set up. I knew you were a zoomer all along.

My comment had only a tangental applicability but you were the one saying that there was no more loss of pixels,which of course there is, This is much much more cogent in a discussion regarding what we see on our screens than the film resolution which is in excess of what we can present with our 1080p projectors, in any case ,if it is 35mm or greater.

This explains a lot regarding your zeal for CIA ; this is one of those come clean moments.



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post #188 of 208 Old 04-28-2009, 06:12 PM
 
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Originally Posted by Art Sonneborn View Post

I'll go there any time ,at least I've looked at it head to head on a very high quality set up. I knew you were a zoomer all along. This explains a lot regarding your zeal for CIA ; this is one of those come clean moments.



Art

If it was cut and dried, the largest thread here wouldn't be a never-ending debate.

Chris Dallas's setup: http://www.avsforum.com/avs-vb/showp...&postcount=852

12.5ft wide.

Zooming.

Since you have a CineSlide, do you move the lens out of the path for 1.85 material?
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post #189 of 208 Old 04-28-2009, 07:48 PM
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Quote:
Originally Posted by LilGator View Post

CAVX, you keep saying that, but making up data in a scaler doesn't make the source 1080 lines of vertical resolution all of the sudden. It's just convenient for your lens setup.

With 1.78 being a glass of beer, and 2.35 being a half glass of beer ... pissing in your half glass doesn't make it a full glass of beer.

It works because 1080 x 0.75 = 810 and 810 x 1.3333333 = 1080. What you see on screen is an image made up of 1080 vertical pixels at a given size in relation to that screen. As soon as you zoom, (CIH or CIA) you change the height of the pixels. You can't deney that.

I don't drink beer, so I certainly don't piss in it

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post #190 of 208 Old 04-28-2009, 08:46 PM
 
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Originally Posted by CAVX View Post

It works because 1080 x 0.75 = 810 and 810 x 1.3333333 = 1080. What you see on screen is an image made up of 1080 vertical pixels at a given size in relation to that screen. As soon as you zoom, (CIH or CIA) you change the height of the pixels. You can't deney that.

I don't drink beer, so I certainly don't piss in it

It's still the same source pixels stretched out over the 1080. Adding pixel density only helps if you'd otherwise see pixel structure. If pixel structure isn't visible, how does adding another lens in the path make it look better than zooming? Now I've had the projector you're using, and as ridiculously sharp as it is, it takes about 0.5x screen width seating to see pixel structure- and even then only if you're actually looking for it.

This is still the classic zooming vs lens debate, which hasn't been concluded and never will (unless we see anamorphic HD someday), and has no bearing on a CIH vs CIA debate.

CIA setups can use lenses and CIH setups can use zooming.

To get back to what we were discussing, to say that CIH is superior because you can stretch ratios to fit 1080 pixels tall is false. You haven't acquired a 1080 source, you still only have 800 pixels to work with, stretched over 1080.

At best, 720p on a 1080p display will only hope to look as good as 720p on a 720p display. All things being equal (display specs-wise, contrast etc...) 720p source on a 720p display will look the same or better.

If you're claiming a scaler adding 200 pixels via stretching adds detail over the 800p source, submit photographic evidence. This is completely subjective; you can't say that it IS better, only that *you* PREFER it.

And I don't mean marketing BS like the "screenshots" selling your lenses:



How can anyone take that seriously?

"It really is simple mathematics. 1,080 lines will show more detail over 810 lines (used with the zoom method). The result is an image utilising the full pixel count which will yield a more detailed image.

Lens VS zooming. This is a closeup shot. Lens is the left shot, zooming is the right hand shot."
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post #191 of 208 Old 04-28-2009, 11:04 PM
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Quote:
Originally Posted by LilGator View Post

It's still the same source pixels stretched out over the 1080. Adding pixel density only helps if you'd otherwise see pixel structure. If pixel structure isn't visible, how does adding another lens in the path make it look better than zooming?

I actually did a demo for JVC recently using two of their HD 1080 projectors and projected the same size image side by side. There were several engineers in the room and all agreed that even though the anamorphic lens produced pincushion, the image from the lens was preferred over the zoomed image becuase it had 1080 pixels and not enlarged 810 pixels.

The photos on the site were a simulation to demonstrate the difference. This is very difficult to do given most cameras have compression when storing the image as a JPEG.

Have you actually experienced CIH with a lens?

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post #192 of 208 Old 04-29-2009, 01:58 AM
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There is absolutely no question that using full panel and a lens produces a superior performance to zooming. I've demonstrated this many times in back to back, and simultaneous, demos..

Many people, myself included, have reported findings on the $20k forum. Also, if you use significantly better machines than the JVCs, the difference can be even more marked. PJs with outstanding pixel noise performance ( eg from the HT5000 and upwards) show this very well indeed. Units with the highest subpixel performance, highest fill and best optics...ie DCI units...when using auto zoom and focus, still don't match the pixel visibility performance of full panel utilization with a lens. My own experience, and that of many others, is actually without the use of an external scaler, admittedly thats with PJs who's custom onboard VP, especially scaling, wipes the floor with most external units anyway. Exceptional scaling is neither expensive, nor difficult, to do. Nasty scaling artifact haven't been an issue, on quality units, for some time now. Thats not to say that some consumer level machines dont perform badly in this respect, but plenty do.

Increased use of domestic 4k machines will certainly make zooming a great option. At that level, the zooming can also be accompanied by the required auto focus system (currently absent domestically) that is seen in DCI units. This will certainly be a requirement for large high-end installs. Current 4k machines, especially the Meridian 810, have more serious problems to contend will before they begin to look at that. Recent discussions, at CEDIA, showed all high end manufactures have no interest in providing zoom solutions, as AP provided the best image on their units, these decisions are based solely on PQ considerations alone.

As an aside....There has also been much misleading talk, by those without direct knowledge or experience, regarding the performance of the ISCOIII in terms of light loss and ANSI performance. The ISCOIII being the unit of choice in high end installs. Recent work with ISCO on this and the numbers obtained were always the same.

Light loss= 2%

ANSI loss= less than 5%. That number being primarily due to minute dust particles. Class 1 Cleanroom performance hit was less than 1%

With lens in place a Lumis was still able to deliver ANSI of 1000.

As always, I hope this helps, and is of interest.

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post #193 of 208 Old 04-29-2009, 03:00 AM
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Originally Posted by JeffY View Post

with DCI you don't need to use anamorphic lenses to display the film.

Thats, potentially, a very misleading statement. No projector "needs" an A lens to display a film.

DCI units have a higher fill factor on the larger DMD, this gives rise to less visible structure.

Also, and of more relevance, if you had any real knowledge and experience of DCI machines, you would know that the reduction in pixel count, leading to structure visibility, is mitigated by the use of defocus presets.

Also, on a lesser note, lumens are not a so much of a premium with DCI units as they are generally powerful and have a low fL target to meet (though that number will be changing).

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post #194 of 208 Old 04-29-2009, 03:01 AM
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Originally Posted by JeffY View Post

Anyway you are right, time to move on.

PS Don't feel you need to answer. I'll stay out of this post now.

Thank you.

As I said before, my intent was simply to inform. I clearly explained the use of legacy geometry in current CIH app.

Any time I can help again, just let me know. PM would be best.

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post #195 of 208 Old 04-29-2009, 05:18 AM
 
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Quote:
Originally Posted by coldmachine View Post

There is absolutely no question that using full panel and a lens produces a superior performance to zooming. I've demonstrated this many times in back to back, and simultaneous, demos..

Many people, myself included, have reported findings on the $20k forum. Also, if you use significantly better machines than the JVCs, the difference can be even more marked. PJs with outstanding pixel noise performance ( eg from the HT5000 and upwards) show this very well indeed. Units with the highest subpixel performance, highest fill and best optics...ie DCI units...when using auto zoom and focus, still don't match the pixel visibility performance of full panel utilization with a lens. My own experience, and that of many others, is actually without the use of an external scaler, admittedly thats with PJs who's custom onboard VP, especially scaling, wipes the floor with most external units anyway. Exceptional scaling is neither expensive, nor difficult, to do. Nast scaling artefact havent been an issue, on quality units, for some time now. Thats not to say that some consumer level machines dont perform badly in this respect, but plenty do.

Increased use of domestic 4k machines will certainly make zooming a great option. At that level, the zooming can also be accompanied by the required auto focus system (currently absent domestically) that is seen in DCI units. This will certainly be a requirement for large high-end installs. Current 4k machines, especially the Meridian 810, have more serious to contend will before they begin to look at that. Recent discussions, at CEDIA, showed all high end manufactures have no interest in providing zoom solutions, as AP provided the best image on their units, these decisions are based solely on PQ considerations alone.

As an aside....There has also been much misleading talk, by those without direct knowledge or experience, regarding the performance of the ISCOIII in terms of light loss and ANSI performance. The ISCOIII being the unit of choice in high end installs. Recent work with ISCO on this and the numbers obtained were always the same.

Light loss= 2%

ANSI loss= less than 5%. That number being primarily due to minute dust particles. Class 1 Cleanroom performance hit was less than 1%

With lens in place a Lumis was still able to deliver ANSI of 1000.

As always, I hope this helps, and is of interest.

I think it should be noted that the light loss you talk of at 2% is being compared to the non lens 16:9 LB image which is in fact 77% smaller than the resulting cinemascope image. (It's not 2% duller than the zoomed image of the same size)

So you lose 2% of your light, but the image is now 77% larger..... 1.78 X .75 = 1.33 squares. 1.33 into 2.37 goes 1.77 times. (scope films on 1.78 screens share the same area as a 4:3 film...1.335 squares)

Even if the light loss was 10% compared to the smaller non lens image, it's still 77% larger.

I think some people compare and comment on light loss etc without realising the images are completely different sizes.

The zoomed image is even worse again, noticeable light loss, contrast loss and 33% larger vertical pixels. 810 X 1.33 = 1077.3

I too have demoed this time and time again and not one single person, collegue or friend has said zooming looked better than a decent A lens.
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post #196 of 208 Old 04-29-2009, 06:31 AM
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I was talking about the light loss due to the typical 98% transmittance of the ISCOIII. Simply, that 2% of light lost by virtue of passing through the glass. A properly installed and adjusted (and cleaned....very important, as dust is the enemy of ANSI) ISCOIII has essentially no effect on the image, and absolutely no significant effect.

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post #197 of 208 Old 04-29-2009, 07:24 AM
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Quote:
Originally Posted by coldmachine View Post

There is absolutely no question that using full panel and a lens produces a superior performance to zooming. I've demonstrated this many times in back to back, and simultaneous, demos..

[snip]

...when using auto zoom and focus, still don't match the pixel visibility performance of full panel utilization with a lens.

I'm curious: What, subjectively, was better in side-by-side tests with zooming vs lens? You seem to be talking here about pixel visibility. But if one is zooming and can't see the pixels anyway (which is the case for many) then what is the benefit of adding the lens, subjectively? It wouldn't seem to help the pixel visibility issue.

I know it has long been purported that you get an increase in light output by using the full projector's panel with an A-lens set up, but more recently there have been discussions, and measurements, playing this down insofar as the light increase (due to things like different projector zoom positions in a lens vs non lens scenario) is fairly minimal.

It seems to me that adding a lens is more on the "Do No Harm" level to the signal - helping people get a wider image when throw challenged and/or adding the convenience of the lens/scaler method over zooming, but doing so with less deterioration/distortion the better your A-lens.

BTW, even though I'll be starting off using only the zoom on my projector, I'm an Anamorphic Lens convert at this point. I used to worry about putting a lens in front of a projector and it's deleterious effects, but having seen several Anamorphic lens set ups (E.g. Panamorphs with Epson and JVC projectors, ISCO III with top of line Marantz) my worries evaporated. The set ups looked awesome and there were no real deficiencies that popped out in terms of image distortion or artifacts. I plan to add an Anamorphic lens to my set up at some point.

But what I've never done is a direct comparison of the same sized zoomed image vs using an anamorphic lens, hence my questions.

Thanks,
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post #198 of 208 Old 04-29-2009, 07:41 AM
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I can believe that using an Isco 111 may be superior to zooming. But I can also believe that zooming is superior to using the cheaper prism based lenses.
But Rich raises an excellent point - what exactly is the image parameter that is improved by using an A-lens:
Pixel visibility? - I see no pixels anyway when zooming
Contrast? - please explain how sticking more glass in front of the projector can possibly improve contrast.
Brightness? - reportedly using the full panel buys you an additional 15% in brightness compared with zooming. I have plenty of brightness reserve in my set up anyway, so that is a non issue.
Resolution? please explain how stretching the same information over more vertical pixels improves resolution, if the pixels are invisible anyhow.
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post #199 of 208 Old 04-29-2009, 08:20 AM
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Originally Posted by taffman View Post

I can believe that using an Isco 111 can be superior to zooming.

Yes , you are right, it is, and for me at least ,I can sit closer. With the ISCO pixel visibilty is gone except about 8' to 10' back but with zooming I could see structure even in my second row. I didn't look into light spill, and reduced fL much but the pixel visibility was a deal breaker even if the other issues were reasonably manageable.

Of course ,this all goes back to Lilgaters comment that zooming doesn't throw out pixels which ,of course ,it does and significantly. The rest of this now is side tracking IMO.

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post #200 of 208 Old 04-29-2009, 08:51 AM
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Originally Posted by CAVX View Post

The photos on the site were a simulation to demonstrate the difference.

Here is a simulated image that shows the difference in pixel size more accurately.

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post #201 of 208 Old 04-29-2009, 09:27 AM
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Quote:
Originally Posted by R Harkness View Post

I know it has long been purported that you get an increase in light output by using the full projector's panel with an A-lens set up, but more recently there have been discussions, and measurements, playing this down insofar as the light increase (due to things like different projector zoom positions in a lens vs non lens scenario) is fairly minimal.

That depends greatly on the projector being used. For example Cine4Home found the light "loss" (due to the light passing through the lens) was negligible, thus with throw being kept constant, the lens would result in a ~30% brighter image than the "overscanned" image.

Now the issue is the idea that you zoom the projector thus opening the aperture compensating for the light "loss" due to the larger size. On projectors like the AE3000 where that's a 20%+ difference, then yes, the difference in brightness between zooming and lens is very small. (Cine4home's measurements bore this out).

But if you were to use something more like the Planar 8150 with it's ~7% brightness difference across it's throw, the lens would be significantly brighter.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #202 of 208 Old 04-29-2009, 09:33 AM
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There's also the fact that not all PJs use those cheap zoom units. Most genuine high end units use pro-level, constant apperture, units that don't loose light across the range.


RH...Im not ignoring you, I just need to dash. I will answer you question. Having been asked for a subjective answer gives some room to move.

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post #203 of 208 Old 04-29-2009, 10:16 AM
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Quote:
Originally Posted by CAVX View Post

The photos on the site were a simulation to demonstrate the difference. This is very difficult to do given most cameras have compression when storing the image as a JPEG.

I think those simulations are extremely misleading. The simulated zoom shot shows pixels are bigger in both vertical and horizontal directions - not the case in reality. You could have made the same point with Eric Garci's version and it wouldn't have been a blatantly obvious simulation.

With all due respect, this kind of marketing is like the cable "comparisons" from "see the Monster difference".
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post #204 of 208 Old 04-29-2009, 11:26 AM
 
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Quote:
Originally Posted by CAVX View Post

The photos on the site were a simulation to demonstrate the difference. This is very difficult to do given most cameras have compression when storing the image as a JPEG.

Wow, just wow.

If you did this properly, you'd be using a quality lens on a DSLR captured to RAW and uploaded to the web via PNG.

Poor excuse for a vastly over-exaggerated and false simulation.
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That depends greatly on the projector being used. For example Cine4Home found the light "loss" (due to the light passing through the lens) was negligible, thus with throw being kept constant, the lens would result in a ~30% brighter image than the "overscanned" image.

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There's also the fact that not all PJs use those cheap zoom units. Most genuine high end units use pro-level, constant apperture, units that don't loose light across the range.

The rule of thumb for light loss due to internal reflection is 0.5% per coated surface. As the ISCO has 8 surfaces (4 elements, two groups) this would add up to 4% as a ball park target for the designer. 2% sounds a bit iffy, a bit on the low side. But it's only a small difference.

As Coldmachine says the real light loss - comparing equally sized anamorphically stretched versus zoomed images - is light loss due to the zoom effect in the projector lens changing effective aperture. Actually it's not strictly a "loss", as it's not the A-lens that is losing light. It's the projector gaining more light than a simple application of the Inverse Square Rule would indicate (due to it being zoomed wider) that narrows the difference.

I take small issue with the second quote above. Sim2, for example, offer a range of lenses - short throw and long throw - whose focal lengths dovetail with each other. I can't see why they would do this unless the aperture effect necessitates a new, long throw lens design when a short throw lens is being stretched too far towards the long throw range and is losing its brightness (due to aperture effect) because of it. Admittedly I base this statement only on first principles, as I've tried to get info from Sim2 about the performance of their lenses without much success at all.

Variable aperture zoom lenses are not "cheap". They are standard. In other words, it's fixed aperture zooms that are expensive, not the other way around. Most here with less than $50,000 to spend will have to contend with the "standard" zoom lens and all its problems.
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post #206 of 208 Old 04-29-2009, 02:48 PM
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The rule of thumb for light loss due to internal reflection is 0.5% per coated surface. As the ISCO has 8 surfaces (4 elements, two groups) this would add up to 4% as a ball park target for the designer. 2% sounds a bit iffy, a bit on the low side. But it's only a small difference.

I did clearly state that 96% was the guaranteed figure. 2%, irrespective of what it sounds, is a fact. Thats across a number of units. 96% is the minimum. As you say, the difference is small and not really of great significance. There will be a post on this, and ANSI performance, when work is finalized. If you wish, I will put you on the list to receive a PM when this is done.

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Variable aperture zoom lenses are not "cheap". They are standard. In other words, it's fixed aperture zooms that are expensive, not the other way around. Most here with less than $50,000 to spend will have to contend with the "standard" zoom lens and all its problems.

Thats an issue of semantics, as the machines I was referring to certainly don't use variable apperture as "standard", constant apperture being "standard" in those cases, though your point is well made and taken as such.

The point I was making was that argument that some of the light advantage of using a lens is compensated for, by the nature of variable apperture, does not apply in all cases.

Hope this helps clarify my earlier post.

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post #207 of 208 Old 04-29-2009, 04:13 PM
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CM, PM me pls. Your's is in reject mode.
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post #208 of 208 Old 04-30-2009, 01:39 AM
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CM, PM me pls. Your's is in reject mode.

Done.

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