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I have been gathering various thoughts about contrast and colour correction that I have been reading on here over time and wondered about the possible benefits of a pink goo.


The thoughts relate to a number of points


1 - A number of people are using filters to correct for the lack of sufficient red light in their projector. The principles behind this are obviously sound and have been explained many times


2 - Some people are even using ND filters to lower the output from their projector to lower black levels and give a less intense image from their projector


3 - KBK has stated in the past that "All correction should be done at the screen" which makes sense to me (I think). My understanding is this:


If projector A has 1000 lumens and is projected onto a 0.1 gain screen, and projector B has 100 lumens and it projected onto a 1.0 gain screen, in a perfectly light controlled room, you would get an equivalent picture (assuming everything else is equal - including contrast from both projectors).


It would also be the case, in this perfect light controlled room, that an ND filter that blocked 90% of light, if applied to the 1000 lumen projector, with a 1.0 gain screen would also give an equivalent image.


The issue though is that any room will have some level of either ambient or reflected light, and this will be multiplied by the gain of the screen in exactly the same way as the projected light. In this real world instance, you would want projector A with the low gain screen to negate the effect of this ambient light.


This therefore is the benefit of a grey screen over an ND filter.


With all this in mind, surely the colour correction of projectors should be handled not by a red/magenta filter, but by a red/magenta (or probably pink) screen, because any filter, no matter how good, will block some light and therefore require a higher gain screen to compensate. This higher gain screen would also increase the negative effects of ambient light.


Does this make sense in theory? If so, what are the downsides to producing a pink screen for those who can get accurate colour control on their projectors?


Is it hard to make a pink screen that behaves as consistently across all shades as a coloured filter?


Would a pink screen provide different levels of pinkness depending on the amount of ambient light and thefore prove unworkable for changing ambient/reflected light levels. (i.e. you get a perfectly balanced range of colours at low light levels, but a bright scene would produce more light which would reflect back and be shown as pink?)


I understand there have been some pink screens (or did I imagine that?), but I have not actually heard of anyone using one, so I assume there are good reasons why not?


Or is this all nonsense?
 

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I've seen a sample of the Stewart "retro grey" screen. Actually I think they got this material from one of their japanese partners....but anyway. I liked it. I don't think they produce it, yet.


For straight on viewing it looked great.

However it doesn't keep a consistent look as you move off axis. This is where the whole image starts to look reddish in color.


These screens might be very popular in standard rooms that limit your viewing angle. Or dedicated HTs that have seating right in front of the screen. Great contrast and the colors and whites appeared to be much more vibrant and accurate than the grey screens I've viewed.
 

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yes, as you move off axis you see less of the reflected image and more of the screen itself.


at least that's my theory. There may be other things happening too like certain spectral frequencies are lesser or greater depending on the angle of incedence etc.
 

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Quote:
However it doesn't keep a consistent look as you move off axis. This is where the whole image starts to look reddish in color.
Hmm... Tryg, does this mean that, not only the brightness decrease but also the color actually shifts, as the viewing angle increases? I wonder how does this happen... Any thoughts?


Anyway, the rationale behind the "flamingo" screen is that it would (in part) substitute for the magenta CC filter that can improve the CR of many projectors by compensating for the red deficiency in the light source, correct?
 

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yes, it has a viewing cone.
 

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The problems are in the usage of a material that gives you the tonality you desire, but in a linear enough fashion to be useful to you. Color correction of screens is a wickedly complex and tricky art. You had better be steeped so deeply in the art of coatings' design that people only speak of you in hushed tones. The physics on that puppy is a lot deeper that you think.


But, I have told people before exactly why the coloration of the screen is the best place and idea for correcting the image. I've said it privately to people for quite some time.


WHY?


Well, for one, it allows maximum linearity of control systems in the PJ, maximum amount of light thrown back at the screen, and maximum levels of contrasting to be achieved. No electronic skewing or limits due to bulb color temps. So, linearize the controls for maximum contrast, with a very odd looking color temp of about 10K, and color correct at the screen. In this way, you achieve the same brightness as correcting with filters and such BUT BUT BUT... you get a much more linear characteristic of the contrast and minute changes in that contrast...AND.. you gain about 20-40% more overall CR, period!!!!


It's a no brainer of the highest order.


Good luck with the color balance though. There's the rub.
 
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