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-   -   Differences between ND filter/Gray paint/Grayhawk (http://www.avsforum.com/forum/23-screens/19461-differences-between-nd-filter-gray-paint-grayhawk.html)

Ran 02-21-2001 05:10 AM


Well the subject says it all. In my everlasting quest to improve my 10 HT black level I have been experimenting with ND filters and Gray paint. Now with the introduction of the Grayhawk, I wonder if it will be an improvement over the filters/Gray paint combination?
Any help would be much appreciated!

KBK 02-21-2001 05:21 AM

The grayhawk screen does a few tricks to improve contrasting performance with digital projectors. This is a tremendous advantage when it comes to the subtulties of the image, as seen in your moment to moment viewing. It makes the projected image 'more real', thus helping your 'willing suspension of disbelief'.

The ND filter works, I suspect, but it does nothing for this particular aspect of the 'Black level' problem, and introduces a reflective element (literally) which will smear your contrast range and actually shorten it! And that is the problem in the first place, so why shorten it? I predict the the ND filter will work.. but it will shorten the contrast range to the point that if there where singular 'scenes' that the projector looked very good at before.. the scenes where the projector looks much better (with the filter in place) will actually be FEWER in number! The grey paint works... in a similar fashion as the ND filter, and is actually a better choice (if properly implemented and chosen, and mixed) than any filter... it leaves the projector's inherent contrast range alone. It attemts to deal with such at the SCREEN, which is a better method. Other than that, the contrast range should be attacked directly by the proper manufacturing of the projection unit.

The best match is: one projector, and one exact screen matching... to that projector.


[This message has been edited by KBK (edited 02-21-2001).]

Ran 02-21-2001 08:14 AM


Thank you for your quick response.

I have to disagree with your assumptions regarding the use of filters.
Using an NDx2 filter (50% transmission of light), for nearly a year with my 10 HT has done wonders to this projector.

After properly calibrating this projectors using some techniques offered by Mr.Munsil, I menaged to improve the contrast and the white balance of the projector, but the problem of the black level remained.
Reading through a forum dedicated to the wonderful Sony 400q (I miss you, old friend...), I found out that people are using ND filters to improve the black level.
After some experimentation I decided on a filter which allows 50% of light transmission, leaving the projector bright enough, and improving significantly the black level, by turning the Gray "space" into light black. I must say that many people that visited my apartment were very skeptical at first, but once they saw the difference they admitted that this makes a very big improvement. Dark scenes that once were glowing Gray, and could not be watched, are now much improved.

One more point I have to make is that strangely after placing this filter, and re checking my settings using Avia, I found I had to LOWER the contrast by aprox 10%!

After reading through YOUR posts re Gray paint I decided to paint my white wall Gray, which also contributed to the black level, and also helping with ambient light.

But, I still wonder if painting the wall with much darker Gray, would give me a better result then the Filter/paint combination.
I would be glad to read your comment on the above.


noah katz 02-21-2001 12:53 PM

I also disagree that ND filters reduce (I presume that is what "shorten" meant in this context) contrast. This could only happen if absorption is nonlinear with intensity.

The reflection problem can be dealt with by angling the filter.

However, gray paint or screen is better because they attenuate ambient light reflected from the screen, whereas the ND filter does not.


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