Film-Tech Forum ARCHIVE: Differing color temps wash out screen image differently?

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Posted by Mark J. Marshall (Member # 1409) on 08-18-2010, 01:13 PM:

Ok, I was trying to figure out a short title for this thread without being confusing, but if I failed in that, I apologize.

I need to bounce something off some experts here. I'm trying to understand how different types of lighting impact the image on white screens differently. This is not necessarily about film, but also digital projectors - and portable (or home theater model) digital projectors.

At my real job, I'm constantly challenged by being tasked with setting up a projector and portable screen in a room that has a lot of light... and then trying to make the picture viewable. As you can imagine, it makes me want to pull my hair out, but I do the best I can in each situation. Recently I took notice of a black screen made by Screen Innovations. I posted a thread about it in the Afterlife forum. It caught my attention because one of it's alleged advantages is being able to give a better picture in less than ideal lighting situations - which is exactly what I need.

So I arranged a test at Best Buy. I took my white screen which I always have problems with to the store along with my projector to do an A-B comparison between my screen and the black screen. I set everything up and had them turn their lights all the way up to simulate our situation - and I was frustrated because even though the room was quite bright even my white screen looked pretty good. Much better than it usually does.

I started thinking about the differences. The Best Buy room has no fluorescent lighting. That could be part of it. There's also no sunlight there. That could also be a part of it. But it still felt strange because their room was not exactly dark. It was pretty bright in there. And still my white screen looked "ok" - and usually it looks nowhere near ok.

So I'm trying to understand a few things. Does the temperature of the light in the room have anything to do with how much the light will negatively impact the screen image? Is something I can't see (ultraviolet or infrared light) impacting it? If so, is there a way to filter those things out of the light? Are florescent lights to be avoided at all costs? What are some of your experiences with this?

Thanks.

Posted by Robert Minichino (Member # 3495) on 08-18-2010, 01:33 PM:

Is your white screen a gain screen? In an office setting, the fluorescent lighting is generally very well diffused, so there's a good chance that there's some light coming from precisely the direction that will reflect it back into your eyes (bouncing off of a wall, perhaps). In the demo room, if the lights are only overhead, then it's possible that there was little light that is being reflected to your eyes.

You can safely discount IR and UV as having any effect other than perhaps irritating your eyes.

Posted by Paul Mayer (Member # 355) on 08-20-2010, 10:46 PM:

I don't think that color temperature has anything to do with this issue.

Usually one goes with a lenticular screen when forced to use a room with light that cannot be dimmed or controlled. Lenticulars are very good at rejecting light that arrives off-axis at the screen. The downside to using a lenticular is a fairly narrow viewing area.

A matte white screen bounces light back equally from from any acute angle to the screen surface. These screens would be the poorest choice in a lit room.

Posted by Mark J. Marshall (Member # 1409) on 08-22-2010, 06:10 PM:

Would some sort of polarized filter or something on the windows help?

Posted by Victor Liorentas (Member # 5272) on 08-22-2010, 07:13 PM:

Perhaps the projection angle was different at Best Buy?

Posted by Paul Mayer (Member # 355) on 08-22-2010, 11:45 PM:

I don't think polarization angle matters - a lenticular screen would reject light coming in from the sides regardless of the polarization angle of the light. Let's face it, if one is going to go to the trouble of putting polarization filters on the windows, might as well just put black show plastic or Duvetyne in the windows to deal with the problem en toto.