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Discussion Starter #1
I recently obtained a Bausch & Lomb Cinemascope attachment ( 2X anamorphic for 35 mm cinema projectors, 1955 manufacture) and have successfully (sort of)implemented it in a 2.35: 1 set up with my BENQ 6200 DLP.

By using Theatertek's custom aspect ratios, I am using full vertical resolution with minimal loss of horizontal resolution (thin black bars left and right sides).

The good news is that there is no noticeable uneveness in focus accross the entire screen and the picture quality is stunning compared to my old MAGANARAMA 1.75X anamorphic that I have been using in the past.

I discovered that the astigmatism adjustment on this lens could be set to closer than the minimum of 50 feet by turning it past this setting and pushing the front element housing down to it's maximum depth within the lens body. This in effect provides a projection distance that I estimate to be at about 20 feet or so.

At the moment there is some vignetting due to the projector's relatively short throw lens and that the B& L needs to be positioned closer to the projector's lens (modification required).

So, if anyone has a 4:3 projector and wants a cheap 2.35:1 CH set up, this can be done with surplus 35mm cinema anamorphics :D
 

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Ziggyr,


So this lens is a fix stretch of 2.0:1?


Does the lens stay in place all the time?


How you go about projecting 16:9, 1.85:1 etc program?


Before I built my diy lens, I bought a 2nd hand Prominar H16 (off a 16mm projector) but would need a scaler or HTPC to apply the required amount of horizontal squeeze, but vertically the image works fine, even with my very short throw projector...


Mark
 

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Mark, yes, this is a 2X lens giving a stretch of 2.0. The lens does not stay in place all the time - I move it away and replace it with the other 1.75X lens and change aspect ratio settings through Theatertek to achieve 1.78 :1/16:9.
 

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Very cool :) So have you got them mounted side by side on a sliding rail?


Mark
 

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Ummmmmm????.........not yet.......too lazy......but will do soon :rolleyes:
 

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I think you be better off using a short throw ISCO film projection anamorphic lens attachment; far better optics than the old B&L thingies (btw, I own both brands)...


-THTS
 

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Discussion Starter #7
Frank, you may be right, but it seems to do a far better job than my other anamorphic....so I'm happy.
 

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Quote:
Originally Posted by ziggyr
I recently obtained a Bausch & Lomb Cinemascope attachment ( 2X anamorphic for 35 mm cinema projectors, 1955 manufacture) and have successfully (sort of)implemented it in a 2.35: 1 set up with my BENQ 6200 DLP.

By using Theatertek's custom aspect ratios, I am using full vertical resolution with minimal loss of horizontal resolution (thin black bars left and right sides).

The good news is that there is no noticeable uneveness in focus accross the entire screen and the picture quality is stunning compared to my old MAGANARAMA 1.75X anamorphic that I have been using in the past.

I discovered that the astigmatism adjustment on this lens could be set to closer than the minimum of 50 feet by turning it past this setting and pushing the front element housing down to it's maximum depth within the lens body. This in effect provides a projection distance that I estimate to be at about 20 feet or so.

At the moment there is some vignetting due to the projector's relatively short throw lens and that the B& L needs to be positioned closer to the projector's lens (modification required).

So, if anyone has a 4:3 projector and wants a cheap 2.35:1 CH set up, this can be done with surplus 35mm cinema anamorphics :D
Ziggy,

All this sounds great to me. Do you have a few photos to share of your setup? Which B&L lens do you have? Is it 1.75x also? Can you share more details on your lens modification? Thanks, CMRA
 

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Quote:
Originally Posted by Frank J Manrique
I think you be better off using a short throw ISCO film projection anamorphic lens attachment; far better optics than the old B&L thingies (btw, I own both brands)...


-THTS
Frank,

Could you elaborate on this? The model number and the stretch ratio? Might as well seek out the best, right?

BTW, what if any modifications did you make? Thanks, CMRA
 

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Hi CMRA. Will take some photos when I get a chance. The B&L I have is the standard 2X one with the red threaded locking ring. Didn't have to modify the lens - focus seems fine at 20 foot projection distance. There is some cut off on the edges of the image. Better to use projectors that have a longer throw lens rather than the very short throw on my BENQ.
 

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And thats really only due to the physical size of the lens. If the lens were larger, this clipping would not be a problem...


Mark
 

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Quote:
Originally Posted by ziggyr
Hi CMRA. Will take some photos when I get a chance. The B&L I have is the standard 2X one with the red threaded locking ring. Didn't have to modify the lens - focus seems fine at 20 foot projection distance. There is some cut off on the edges of the image. Better to use projectors that have a longer throw lens rather than the very short throw on my BENQ.
By any chance does it look something like this:
 

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Discussion Starter #13
CMRA, no, that's the ''jumbo'' version. Should be better than the standard one. However, the problem of vignetting also relates to the distance between the front and rear elements which is significantly more than say an Isco III.
 

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Quote:
Originally Posted by CMRA
Frank,

Could you elaborate on this? The model number and the stretch ratio? Might as well seek out the best, right?

BTW, what if any modifications did you make? Thanks, CMRA
Boy...am I late in answering this one! :eek: Sorry about that...


I mentioned the theatrical short throw anomorphic lenses availability (they still have a 2x stretch factor; any Isco theatrical anomorphic series/model would do...depending on how much you want to pay, of course), but I don't use the ones I own for HT video purpose; they're solely used for film projection.


I still have and use the original ISCO I lens attachment, which is known to have an stretch factor that's over the required aspect ratio (for older 4:3 projectors); it produces some visible artifacts...like an slight bending of the top and bottom of the image (it almost looks like one is using a curved screen!) in addition to the over stretch (I have to move the Dukane 9015 D-ILA projector closer to the screen in order to contain the entire image within it).

The ISCO II and III version are supposed to take of that that "problem"...


-THTS
 

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So, how is a 2X squeeze cinema anamorphic going to work with a format that requires a 1.33X squeeze? It sounds to me like apples and oranges. Cinemascope/Panavision 35/all cinema anamorphic formats are 2x because that is the squeeze that the lenses have when shooting the movie. Same at the front end, same at the back end. If you use a 2x projection lens when the source material has a 1.33x squeeze, you are going to be overshooting 2.35, and geometry will not be correct.
 

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That was why we were discussing using a 4 x 3 projector not a 16:9 unit with such a lens. Whilst a frame of 1.33:1 is not quite right either, it can be made to work with minimal horizontal pixel loss where the 16:9 unit would sacrifice too many to be worth it...


Mark
 

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Discussion Starter #17
Mark is correct. I use a HTPC remember to alter the original squeeze factor plus some zoom through Theatertek to maximise the use of pixels within the 4:3 frame.
 
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