Shelf for Projector and A-Lens: Danger of reflections? Necessary for it to be black/low reflectivity? - AVS Forum
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post #1 of 11 Old 05-03-2013, 09:31 AM - Thread Starter
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I'm just re-building a new shelf for my projector and with a Panamorph UH480 anamorphic lens and it's automated sled.

Previously my shelf was painted matte black and this new one will be as well.

However, I'm wondering if ensuring low reflectivity of the projector/lens shelf is actually important, and if so how important? In other words, are there reflections, light leaks from projector lenses, including possibly light bouncing between the A-lens and the Projector lens, that would affect image contrast and require absorption? And if that's the case, if I have the choice between painting the projector/A-lens shelf a flat matte black or going with an even darker surface coating for the shelf (e.g. Prostar material or even black velvet?) would this make any difference?

We have certainly seen that in terms of light reflections a dark black velvet-like material is better than any black paint, and I'm just wondering if this might also play out in the choice of finish on a projector/A-lens shelf.

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post #2 of 11 Old 05-03-2013, 05:12 PM - Thread Starter
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post #3 of 11 Old 05-03-2013, 11:55 PM
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Kelvin has a white shelf for his JVC and lens set up, so you could ask him. He has pics etc over on the UK forum.

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post #4 of 11 Old 05-04-2013, 07:56 AM
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There is some back reflection from the various lenses. However, I think it might be easiest just to see what residual light your seeing and then make appropriate baffles out of black velvet. That would take care of the majority of concern. Unless your making the entire room black, my guess is that with good baffling you'’ll get more back scatter from the screen image light bouncing off the walls, furniture, clothes, etc. than what would come from the projector/lens back reflections.

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post #5 of 11 Old 05-04-2013, 10:56 AM - Thread Starter
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Thanks Gary and John.

My room is a black velvet "cave" so the room isn't an issue, which is why I care about any residual problematic reflections
near the projector. I've never really heard of any talk about this before, though I know some projectors leak some light around the front or lens area. I guess I'll just see what things look like once I'm finished.
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post #6 of 11 Old 05-04-2013, 05:13 PM
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Quote:
Originally Posted by R Harkness View Post

Thanks Gary and John.

My room is a black velvet "cave" so the room isn't an issue, which is why I care about any residual problematic reflections
near the projector. I've never really heard of any talk about this before, though I know some projectors leak some light around the front or lens area. I guess I'll just see what things look like once I'm finished.

Make the shelf depth so that you can place the lens at the front edge. That is what I did.

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post #7 of 11 Old 05-07-2013, 12:15 PM
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As Gary says I have a shelf, but the upper face is just bare MDF (only the sides and underneath are painted light grey to match the wall). I can't really see any 'light peaks' or other issues that might be effected by the light coloured shelf, but my room currently isn't ideal anyway so I have more important issues. The only thing I would be concerned about is heat since this black material would be very close to the projector, but my black Isco II lens doesn't seem to get unduly hot so perhaps that's not an issue anyway.

I think you've probably seen my 'floating shelf' I built earlier this year, but here it is with the Isco in place as well: The Isco is right at the front edge of the shelf so any reflections coming out of the lens would hit the black stand rather than the shelf (nothing visible on the ceiling either as I have looked for this in the past).


Zooming: Been there, done that, bought the lens...
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post #8 of 11 Old 05-07-2013, 03:30 PM - Thread Starter
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Thanks boys.

I did my new shelf in matte black as I intended anyway. Plus, the A-lens beam clears the front of the shelf anyway.

(I'm still having trouble dialing in this A-lens, though. There seem to be so may parameters to get right - get my projector perfectly flush/plumb to the screen, get the lens straight with the projector, but wait, the lens pattern is a bit off on the screen...so have I not got the projector aligned with the screen, or is it the A-lens that is not aligned with the projector, or with the screen, or both? It's hard to tell which parameter to change).
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post #9 of 11 Old 05-08-2013, 04:48 AM
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http://www.panamorph.com/8-support/videos

Have you watched the 480 install video? It should answer your questions.

It is important that the projector be square with the screen and the horizontal lens shift centered. Use of vertical lens shift is fine, though.

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post #10 of 11 Old 05-08-2013, 07:17 AM
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Quote:
Originally Posted by R Harkness View Post

Thanks boys.

I did my new shelf in matte black as I intended anyway. Plus, the A-lens beam clears the front of the shelf anyway.

(I'm still having trouble dialing in this A-lens, though. There seem to be so may parameters to get right - get my projector perfectly flush/plumb to the screen, get the lens straight with the projector, but wait, the lens pattern is a bit off on the screen...so have I not got the projector aligned with the screen, or is it the A-lens that is not aligned with the projector, or with the screen, or both? It's hard to tell which parameter to change).

Hi Rich,

Would love to hear your impressions and any setup/dialing-in tips about your A-Lens integration when you are finished! biggrin.gif

Some pics would be great also!


... Glenn smile.gif
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post #11 of 11 Old 05-08-2013, 04:53 PM - Thread Starter
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Quote:
Originally Posted by John Schuermann View Post

http://www.panamorph.com/8-support/videos

Have you watched the 480 install video? It should answer your questions.

It is important that the projector be square with the screen and the horizontal lens shift centered. Use of vertical lens shift is fine, though.

Yes thanks I've viewed it. I've squared the projector image, no horizontal lens shift, some vertical shift downward.

BTW, something curious about that instruction video: It recommends to use the projector's lens pattern to test the geometry when setting the lens, and a JVC projector is being used in the demo. I have a JVC RS55 projector. When I first tried to set up the lens using the projector lens pattern I was being driven nuts because it seemed that once the lens was in the path I could never get good geometry. After a while it hit me: even though I'd hit the anamorphic stretch button on my remote, the projector was not, in fact, applying any stretch to the lens pattern. It can't do this - it can only apply anamorphic stretch to picture material. So obviously each time the A-lens was in the path it was warping the non-stretched image.

I had to resort to using patterns from the Spears and Munsil calibration discs to get around this. It seems to me this would not be the case only with my particular model, so it's curious it was no issue in the video demo above.
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