Video Projectors

Measurements

Two claims on TAW's website snagged my attention: gray-scale at 6500K across the entire brightness range of 5 (!) to 100 IRE within a ±300 range; and no convergence drift. In my experience, the first might be achievable at a low overall peak-white contrast adjustment, but with the latter I had to choke back a chuckle. All CRTs drift, although some projector designs require much more effort to maintain image perfection. I was eager to see how this chassis behaved.

For the gray-scale adjustment, my procedure was to use frames 11 and 12 of title 17 on Video Essentials, which correspond to 30 and 80 IRE on a scale of 100 divisions from black to maximum white level. When he created this disc, Joe Kane placed these frames next to each other for rapid toggling between them during calibration, as the adjustments of the dim and bright ends affect each other. Experience with two-piece CRT projectors has taught us that we simply can't use the 20 and 100 IRE windows for measurement; most projectors have some sort of gamma correction, and adjusting at these points guarantees a big blue hump through the middle of the gray scale.

The HD-800 was no different. Over many trials, the best we were able to get was within +600 and -400 on an average of 6400K, but that was at a peak-white level of nearly 10 foot-Lamberts. While TAW's claims are a reach, the actual performance of our review sample was still very, very good.

As for drift, the HD-800 did require periodic touch-ups for perfect convergence, but these were very minor—this is one of the most stable CRT projectors I've ever lived with. The difference between convergence at cold startup vs. fully warmed was negligible, something I almost never see in CRT units.

Black-level retention was excellent, as one would expect from a chassis designed for professional use. Geometry and linearity were passable after the factory setup. During subsequent setups with the various processors and Pat's HTPC, I was able to develop a technique in Green Random Access Convergence to make both geometry and linearity quite perfect, making pans and zooms fluid and linear.

The TAW HD-800's calibrated gray scale is shown in Fig.1. It tracked very well; with the exception of the extreme low and high window test patterns, it was within 190K of 6330K, and at just under 10fL peak white. —JJG