Lens Quality - AVS Forum
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post #1 of 8 Old 10-15-2012, 07:26 AM - Thread Starter
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A newcomer to this forum and one who came from the UK cine film stable of the early and late 60s; I am now hooked on the video projector system and the amazing quality one achieves from this technology. I have had two projectors, both Optoma, the HD65 & HD20 and am now considering the Benq 7000 for reasons such as lens shift ability and quality which in the case of the former (and for my purposes) I consider a real advantage.

I have read a number of review comments in this forum about the 7000 many of which relate to sharpness of the image obtained from the HDMI input signal compared with the vga signal, also the many explanations and firmware issues.

Coming to the point of my thread - never has the lens quality been mentioned and yet in my days, lens quality issues were all it was about other than punching enough light through the film gate! In fact in all the reviews I had read in many forums and articles, lens quality, light transmission and aberrations issues never seem to be mentioned - in fact it is almost a part of the video projector that is not part of it, if you see what i mean!

Maybe it is my lack of knowledge of video projection technology that I look for and consider issues that relate more to film technology but with the amount of words expended on the BenQ 7000 sharpeness issue it seemed to me that lens quality had been forgotten. Finishing on a positive note, what a joy it is not to have the worries of sprockets tearing, hair in the gate, splices coming apart and all the many problems one had to face with film.
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post #2 of 8 Old 10-17-2012, 04:28 PM
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Not that it's completely unimportant, but in digital projector systems the bottleneck in quality is typically not in the optics path but in the technology generating the image (ie dlp, LCD/lcos etc), followed by bulb and iris implementation.... lens quality matters but it is usually swamped by things causing magnitudes more deficiencies. In a pure optical system, of course it's all about the optics! Actually it wasn't... how the film was produced was vitally important, its just that that step was done remotely and hidden from you. Now it largely occurs inside your projector, for better or worse.

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post #3 of 8 Old 10-18-2012, 12:11 AM - Thread Starter
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Thanks for your reply BIGUS, Yes I take your point, the technology in creating the image within the projector is more of a challenge than the optics.
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post #4 of 8 Old 10-22-2012, 09:14 AM
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Probably the biggest reason you don't see it mentioned is probably that lenses aren't interchangeable so there's no way to isolate the lens quality from any other part of the projector. The only "important" part is the end result, and it's the only thing that can actually be evaluated.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #5 of 8 Old 10-22-2012, 11:53 AM - Thread Starter
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Not entirely true as some projectors offer lenses of varying focal lengths, eg short throw and long throw for achieving desired projector placement in respect of screen.
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post #6 of 8 Old 10-23-2012, 09:26 AM
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True, but it's not like you can replace the lens your projector came with, with a better one, or chose from good/ok/poor lenses when you buy a projector.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #7 of 8 Old 10-27-2012, 03:15 PM
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Quote:
Originally Posted by Brookdene View Post

Coming to the point of my thread - never has the lens quality been mentioned and yet in my days, lens quality issues were all it was about other than punching enough light through the film gate!

Just my $0.02 worth. Lens quality does make a difference and one reason BenQ projectors are now in the sub $3K bracket is because they compromised on lenses for the last few models (W5000/W20000.W6000/W6500 and now the W7000). If you go back a few models (W9000), these projectors were all in the high 4 figure price ranges.

They gave up the motorized focus and zoom options and the only way to further reduce costs was to drop the quality of the primary lens. I've seen examples where you can not get uniform focus across the screen. I documented one case to which BenQ agreed to replace the lens.

Mark Techer

I love my Constant Image Height system!
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post #8 of 8 Old 10-27-2012, 07:23 PM
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Focus Test Patterns
I have a reasonably full and growing list of 1920 x 1080 focus aids and other test patterns (both static and animated) on my web site, that are available for use or download free of charge.

They specifically address some of the more common problems encountered with optical quality and focus.

There are also contrast charts - ANSI and ON/OFF - and a couple of aspect ratio charts that buy into the interminable "2.40 v. 2.35" war, seeking to put some facts on the table.

If you've got a dud optical system or anamorphic lens, these won't make the image any sharper, but they'll at least give you an unbiased tool to use for evaluating optics.

http://www.xeitoptics.com/test-patterns/
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