Originally Posted by BobL
There is no free lunch with any of these screens. I should probably explain further and define a gain screen. A gain screen has a coating or optical layer that is designed to reflect light other than being perfectly diffuse. A screen with no coating can be seen from all angles with no change in picture quality and it also does not matter where the projector is placed, you will still see the same image everywhere. This is called a lambertian surface or lambertian reflectance. The overall gain of the screen is misleading, I'm mainly concerned with what this optical layer does to the picture.
A screen starts with a base material and that color can be different. This alone will change our overall gain and can color shift the image. A reference material is similar to chalk and is a magnesium based compound. So if our base material is gray we have a gain less than one. But we can still have good viewing from all angles. If the base material is whiter that the reference it is often said to have a positive gain, usually a small amount like a 1.1 gain and still maintains good viewing angle from everywhere.
People that have a reference material and are in the 'bat cave' environment will tell you there is no better picture and they are correct. Once we apply an optical coating or layer, light is being bent and our picture is being distorted. Someone had posted pictures of an HP old and new version under a microscope or magnified, do this with a projected image and you will see the pixel distortion especially compared to a reference screen. This is a tradeoff we make to correct for other problems of a given environment.
Any screen that has these optical coatings/ layers has to be used in the right combination of projector and audience placement to minimize these distortions. But even in the best set up for a given screen some distortion still exists. That distortion can come as lack of screen uniformity, hot spotting, color shifting, sheens, glimmering, sparkles, etc. The HP and DNP are no exception.
With a retroreflective screen it is best to have the viewer as close to the audience as possible, which of course is impossible to get perfect or you'd block the image:-) Also, retroreflective materials are not perfect in their reflectivity and often have color shifts with minor amounts of off axis viewing. I did say in general it is best with a longer throw but there are exceptions depending on the screen design. Also, with angular reflective screens it would help to have a curved screen but you might need need a different lens to account for pincushion.
With any gain screen they are said to reject ambient light. This is simply not accurate. They do not reject ambient light they just don't reflect it back to the audience. If there is a light to the side of a screen that light with an angular reflective screen would be easily seen on the other side of the screen. It just wouldn't be seen in front of the screen. If it was a retroreflective screen the light would be reflected back towards the light but again not in front of the screen. Now a screen can be designed to have different characteristics in the vertical and horizontal axis. Sometimes this is done with multiple optical layers/coatings like the DNP.
So let's use a simple example of 2 different screens, The Studio Tech 130 and Firehawk. A 1.3 gain vs a 1.25 gain so it should be very similar? Why does the Firehawk have less viewing angle with less gain? The answer is it doesn't have less gain. I'll use some estimated figures as I don't know their exact ratio.
Say the Studio tech 130 starts wtih a reference 1.0 gain material and applies a 1.3 gain coating for an overall 1.3 gain.
The Firehawk starts with ~.83 gain screen and has a 1.5 gain coating for an overall 1.25 gain.
This is a simplications but overall gain does not tell all the characterisitcs of a screen. I'll let any DNP guys that might monitor this forum talk specifically about how their layers are used to give the results they are trying to achieve and what environments it is best suited. No screen is best in all environments no matter what :Dthe salesman says
I hope this helps with a little primer on screens and choosing the best screen for your environment.