CurtPalme.com Home Theater Forum

[Joust]

Hi,
I'm looking at brocures for Digital Projectors. (NO, I'm not considering one) and they quote 2000 ANSI lumens.
my Marquee quotes 250 ANSI lumens and 1200 peak Lumens.
so are the digitals in reality Peak or ANSI lumens. I want to be able to compare apples to apples.

[garyfritz]

Digitals are pretty much the same on ANSI and Peak. They have the same max lumen output (per area) whether you're displaying a window, a checkerboard, or a full white screen.

CRTs are current-limited, and it takes current to display bright areas. As you display a larger and larger bright area, you hit the current limit, and the projector drops its max brightness level to keep within the limit. So their peak lumens (on a small area) are much higher than the lumen output on a full-white screen.

So yes, assuming everybody measured the same, that digital really is 8 times brighter than your Marquee! At least, it is on an ANSI lumen test. On actual video content (unless you're watching Ice Age or something else with tons of bright-white scenes) there won't be as much difference. The Marquees have a peak lumen rating of 900-1300 depending on model, so for actual video content, the digital might only look about twice as bright.

[Joust]

well, how much does that suck?

[Rdean]

Stack. Pretty soon everyone's gonna be doin' it right? I may have to give in someday...

[Joust]

[ecrabb]

Don't forget that 2000 ANSI lumens figure is the day you take the projector out of the box. It starts going down hill from there. Depending on the projector and bulb in question, it could be down to as little as half that 2000 ANSI lumens in 1000 hours. Also consider, that in a dark room, on a reasonable size screen, most of our CRTs are plenty bright, even in mixed scenes. Consider also, that unless you like watching a lot of movies about going from dark caves into snowy fields, it just doesn't matter that much. I'm not willing to sacrifice everything I like about CRT and tolerate everything I don't like about digital just to get more brightness and a little box. It still looks like it's going to be at LEAST 2-3 years (if not more) until the cost/benefit mix will start looking acceptable (justifiable money-wise) to me on the digital side.

SC

[Joust]

Good points, I agree, ecrabb
It still sure would be nice to get a new source for better tubes at a cheaper price

[garyfritz]

Good point SC. In fact lots of bulbs end up with 40-50% drop in lumens in much less than 1000 hours -- I've heard as little as 300-400.

Also, you very seldom get anywhere near the rated lumens by the time you calibrate the display.

I figure I'll stick with CRTs until they perfect LED light sources or something similar. I don't want a hot bulb that degrades rapidly, costs a ton to replace, bakes the optical path, etc. I also don't want DLP because I see rainbows. On the other hand I don't especially want a 3-chip solution with non-correctable convergence errors either. I hope within 5 years they have a better technology. If not, I may be scouring ebay for another CRT.

Joust, I don't think your Chinese manufacturer could increase the lumen output that much, even if he adds antifreeze. We're already pushing the phosphors about to the max. About the only ways to increase lumens are to push the phosphor harder (which burns it out much faster) or increase the phosphor area (can you say 9"? ). Unless you're going to start manufacturing 10" or 12" tubes, I don't think there are many options to increase the light output. You're better off to stack.

[Joust]

ok ok you talked me into it.
now all i need is a newer green tube that i can put in my bench machine.

[papalek]

Maybe if you could actually make a glycol circulation system.


What if you used the fill holes to be outlets and inlets for glycol to be circulated. You could run lines to a refrigeration system to keep the glycol real cold and consistently cold. If the face of the tube was kept cold, you could turn up the contrast and not burn the phosphors.


Am I on the right track or am I barking up the wrong tree.

[Joust]

Cool overclocking CRT projectors

[VideoGrabber]

Joust asked:
> well, how much does that suck? <

Not much at all. Really.

[Joust]

[ecrabb]

I think "burn" is really a misnomer. Maybe somebody could chime in with a better description of the actual chemical process, but I think it's more along the lines of oxidation (not that it is - I know, little oxygen in the tubes, but more like that), than it is anything getting hot or burning. I think the coolant serves two purposes: 1) Keeps the glass from breaking from the thermal stress, and 2) Keeps the tube face at an overall cooler temp, which does extend the life (or decelerates wear process (whatever the process technically is).

SC

[Joust]

i think when it is turning brown, it is indeed burning. Perhaps when it looks black it is either burned really badly or has vaporised inside the tube so its simply not there on the tube face anymore. purely speculation on my part.

[WTS]

Speaking of phosphor usage, wouldn't using 1080i instead of 1080p make your tubes phosphor last longer? I've often thought about this but could never arrive at an answer.

[VideoGrabber]

Walter,

if you had everything set up for 1080p, then dropped it to 1080i while changing nothing else, would the perceived brightness drop? If so, then when you adjusted contrast to get back the same level of "punch", you'd be back at the same wear level again.

In general, phosphor wear is a function of beam current and time, the same factors that govern light output. While you can decrease wear by measures like reducing screen size, increasing screen gain, utilizing maximum phosphor area, and (to a lesser extent) controlling the environment (dark walls, etc.); to produce a specific desired amount of light output will mean driving the tubes just as hard, whether it's with higher currents for shorter intervals, or lower currents for longer intervals. TANSTAAFL.

[WTS]

Okay, looking at it that way does make sense, thanks.

[ecrabb]