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post #1 of 10 Old 03-08-2007, 07:34 AM - Thread Starter
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Does anybody know a source for 86mm ND filters in .1 and .3 to reduce the light output of a digital proj. by 21% and 37% respectively , B& H dont have.
Thanks,
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post #2 of 10 Old 03-08-2007, 10:56 AM
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I've not seen any glass filters that are less than ND2/50% (0.3 is the photographic equivalent of ND2 isn't it?), and the plastic or gel filters of those values offer poor pass through quality that will effect the image.

I think there is a variable ND filter but it was quite expensive (ideal for a dimming lamp).

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post #3 of 10 Old 03-08-2007, 11:07 AM - Thread Starter
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.1 is 1/3 stop , 20% reduction and .2 is 2/3 stop , 37% reduction
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post #4 of 10 Old 03-08-2007, 11:26 AM
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Quote:
Originally Posted by neilher View Post

.1 is 1/3 stop , 20% reduction and .2 is 2/3 stop , 37% reduction

Thanks. So 0.3 is 1 full stop and 50% like an ND2.

I did pick up a 0.1 Kodak Wratten (plastic type) filter once, but that was a couple of years ago and they seem to be quite rare. They're relatively cheap so might be worth experimenting with if you can find one. They can crinkle and deform when in close proximity to bright lights though - a friend tried one on a Sim2 HT500 and it did just that, so you'll have to try to use it as far from the lens as possible. Even then it can fade over time.

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post #5 of 10 Old 03-09-2007, 10:31 AM - Thread Starter
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hey guys ,
somebody must have a source for these filters, I am sure other people may be intrested, I tried B&H, andorama, filter comnnection, it seems the .1 & .2 are the diffuculty, the common one is .3 / 1 f stop which I believe will cut output by 50%, too much fo me!!!!!!!!!!
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post #6 of 10 Old 11-29-2009, 08:00 AM
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I looked around and had the same difficulty. So I will probably just use a .3. The reason I suppose is that ND filters are generally used by photographers to decrease shutter spead for long exposures with over exposing. They aren`t made with videonerds in mind and I can`t imaging a photographer needing just a 1\\3 stopND filter.Obviously cutting light by 50% in FPl and is a big cut but a 1 F stop cut for a photographer wanting to make a long exposure normally would not be much.

I have a projector with a very high optical quality lens with decent but less than steller blacks but which puts out lumens to spare. My intent is to cut the black ref level some. I do not want to degrade the optical quality of the lens nor doi want tolower its ANSI. While the lens will take a screw on filter I am concerned that placing any ND filter there would cause some of the light that would otherwise exit the projector lens to be reflected back into the lens thus reducing ANSI CR. I have concluded that the ND filter should be mounted some what away from the front lens element and be set at some angle (not parallel) to the lens front element in order to direct reflected light away from the lens. I wonder what the ideal angle would be. I want to obtain the highest quality ND filter (don`t even think of suggesting gel, plastic, hoya, gefen etc I want the best. Might that be Schneider? I amprepared to spend say $200 for the filter. I amt hinking of using a 4 inch by 4 inch piece of filter materia land mounting it in a Lee holder and attaching that to some sort of gooseneck flexibe attached to a chief ceiling mount. Please do not jump in with how pleased you are with your screw in $35 Hoya. I`d rather hear about the screen youmade froma bed sheet. Just kidding. Tnanks in advance for the help.

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post #7 of 10 Old 11-29-2009, 07:28 PM
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Something like this?
Think this is a Schneider ND filter that I used on my PJ.
Just used the 4th mounting arm and made a filter holder from some metal I had laying around.
I've done some checks with test signals and I can't see any difference with the light reflected back into the lens by eye.
The Projection Design projector I have does have a fixed Iris that might be stopping some of the light getting back on the DMD.
Since I took this photo I've rotated it off axis a bit but you'll reflection some light back into the room from the filter.
I can also slide out the filter if I need some more light or when the lamp gets a bit old.
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post #8 of 10 Old 11-29-2009, 09:15 PM
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That`s exactly what I have in mind for my Samsung SP-A900B. I would think it doesn`t take much back reflected light to screw up ANSI CR in any projector. The best experiment would be to measure ANSI CR without the filter,the filter parallel to the lens and then tilted at various angles. I like your set up but I will add a gooseneck to allow tilting. Since the .3 ND filter will cut light by 50% I will run the iris in manual wide open except when I switch on the DI and the machine will vary it. I may have to run the bulb in high but we shall see. I don`t like setting irises to partially closed because the ANSI CR is cut by reflections and on some machines like the Samsung the MTF decreases as the iris opening decreases. That`s the reason I am going to a ND filter. Something is needed to improve the blacks and the iris to me is not a solution because of the reduction in MTF.

My room is black so light reflected off the filter if it is tilted should not be a problem.

Thank you very much for your posts and photographs. Ii wish I could find a high quality glass 0.15 ND but they apparently not surprisingly don`t exist being made for photographers who would have no use for a 0.15..

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post #9 of 10 Old 11-30-2009, 02:44 AM
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I did run some ANSI checker board test patterns, plus every other test pattern that I could find when I first put it up and no matter how I looked at the image I couldn't see the filter effect the image.
I even ran with the filter half in/out but there's was quite a large transition area in the middle.
As you suggested I also tried the filter at 45deg and square on to the lens.
A byproduct of the design meant that I can rotate the filter position and even move in back & forward if needed.
At the moment I have it about 20deg to the lens.

This filter is a Schneider 4x4 ND.3 P/N 68-040344 (water white glass).
Even though this filter knocks off half the light it's surprising how your eye gets used to the image.
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post #10 of 10 Old 11-30-2009, 05:34 AM
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I had a CRT FP for many years so I know about one`s eyes adapting to low lumens. The filter you have is the one I am ordereing. Costs about $175 US from Adorama.

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