Setting up the Test
To see how DLP and 3LCD projectors can differ in their display of color, we selected two WXGA projectors (one 3LCD and one DLP) built for larger conference room applications. They had similar ANSI lumen specs above 5000 lumens, and both were rated at 2000:1 contrast. Since the goal of this study is to explore the weaknesses of 3LCD and DLP technologies as they relate to ANSI lumen and CLO specs, by prior agreement with those who supplied us the test units we will not disclose the models used. We are grateful to those who contributed the equipment, and for their willingness to support this study.
To guarantee screen neutrality we used an 11-foot wide Studiotek 100 supplied by Stewart Filmscreen. Our thanks to the folks at Stewart for providing this product. The Studiotek 100 is a perfectly neutral white, 1.0 gain screen, and it is ideal for this type of comparative evaluation. We placed the projectors on racks and projected two 5-foot wide images onto this screen so we could take simultaneous screen shots of both.
Two Tests at Different Calibrations
In the projector world, when you maximize light output you compromise picture quality. Color balance goes out the window, details in highlights can often disappear, black levels are not so black, colors get not so saturated. For many reasons the picture does not look as good as it would if you reduced the light output of the projector to bring these factors into balance. But ANSI lumen and CLO specs are frequently based on the projector's maximum light output, regardless of what the picture looks like, in order to get the biggest numbers for marketing reasons.
By the way, this is not the vendors' fault. The problem exists due to the fact that the ANSI lumen spec has no color balance standard--it doesn't care what the picture looks like, only how bright it is. Meanwhile, professional buyers for corporations, governments and school districts routinely issue Requests for Quote that specify lumen requirements but never stipulate color balance requirements. If vendors are to survive in this world they need to play the cards they've been dealt. At the present time, that means they must market products with lumen ratings that are not based on ideal color calibrations.
SO...given that this is the case, in this 3LCD vs. DLP test we set up the projectors two ways and took side-by-side comparison shots in each:
Test # 1. Brightest Mode, No Calibration: In the first series of test shots we put the projectors into their factory defaults for their brightest operating modes. This shows what they do out of the box with no adjustments, just selecting their brightest configurations. Set up this way, we get the maximum lumen output along with some obviously degraded picture quality.
Test # 2. Reduced Brightness, Improved Picture Quality: In the second series of test shots we adjusted color balance and contrast on both projectors to produce the brightest pictures possible consistent with a more neutral color balance and a sufficient rendering of detail in the highlights. The light output was reduced, color quality on both units improved, and the pictures looked much better.