Brenda,
Your problem with color accuracy of video projectors is a more severe form of the problem of color accuracy on computer monitors and printers. There are 500-page books that discuss why it occurs and what to do about it. The root cause is that given the same triplet of red-green-blue numbers, different devices will produce different colors. For monitors and printers, the general solution is to use a colorimeter or spectrometer to measure the actual color produced by a large range of RGB values, to develop a color profile for the device based on the measurements, and subsequently to display or print images using an application that in turn uses the color profile of the device to compensate (adjust the RGB value) to make the color look right. Unfortunately, it gets even more complicated than this; it comes down to what color a particular RGB triplet (like 150,70,100 on a scale where the values go from 0 to 255) is supposed to look like. There are multiple color spaces (all using RGB values from 0 to 255) that specify what a particular triplet should look like. Digital cameras typically offer you the choice of sRGB and Adobe RGB 1998 color spaces, but these are not the only ones in use. sRGB is a small gamut space defined to be one that most monitors and printers can produce, so camera manufacturers tell you to use sRGB if you don’t know what a color space is. A display application therefore needs to know the color space used by an image as well as the color profile of the output device. Most display applications (e.g. PowerPoint) and web browsers (e.g. Internet Explorer, Safari) don’t know anything about color spaces and color profiles; they just take the RGB values from the file and send them to the output device without any adjustment. I use the sRGB color space for the JPEG files I post to Daffnet since that’s the one most likely to look okay without any color management.
The color profile of a monitor should be measured after adjusting the the brightness and white balance to some neutral point. The monitors on many notebook computers are not adjustable. The white balance on monitors for desktop computers is usually adjustable, but most people don’t know how or don’t want to go to the bother of setting them up to be neutral. The consequence is that every image they see has a color cast. If they use an image editor that doesn’t use color management to edit an image to look realistic on a particular monitor, the edited image won’t look right on another device (e.g. a printer).
I say video projectors have a more severe problem because you can’t put a colorimeter on the wall to measure the actual color. Also, what you see depends on the color of the wall. That’s why you use a projection screen — to get a neutral surface on which to project your image. It is possible to develop color profiles for projectors, but I don’t have the equipment to do it and therefore have no experience with it. When I bought a projector years ago, I got one that purported to handle the sRGB color space correctly. I experimented with that setting and other adjustments but was never able to get the projected colors to look the same as on a calibrated monitor. It’s moderately close but definitely not perfect. Harold Koopowitz has told me that the color from my Mitsubishi XL8U comes closer to realistic than most other projectors he’s seen. This is a fairly old model. I have not looked at any of the new projectors, so I can not tell you whether current models come with software or hardware adjustments that make it easier (or possible) to get realistic color. Getting accurate projected color is a common and difficult problem.
Kirby Fong
Begin forwarded message:
> From: “brenda lyon”