CurtPalme.com Home Theater Forum

[damien55]

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Hi,

I have a few questions about CRT projector calibration using a DTP-94 (Monaco optix)
I've used the DTP-94 for the last 4 years on LCD and CRT monitors with very good results, my plan is to use it to calibrate my Barco 808 using the HTFR software using the tutorial on this website.

My setup is like this:
Projector: Barco Graphics 808 with HD144 color filtered lenses (distance projector screen around 2meters)
Screen: Oray screen fabric on DIY frame 1.75meters wide, ratio 16/9
Source: HTPC
Sensor : DTP-94

I have tried to place the sensor in front of my screen as explained in the tutorial and then tried to maximise the FTL but while I was doing that I realised that the color balance was changing a lot (for exemple the red was way too high and then if I move a bit the blue was too high).

I think the problem is that the DTP-94 doesn’t come with a diffuser and then when you move the sensor the light reflected by the screen changes a lot as we have 3 sources of light (maybe the gain of my screen has something to do with the problem as well).


My questions are:
-Is the problem due to the lack of diffuser and/or the fairly high gain of my screen (1.2)?
-Is my sensor just not good for calibrating projectors (it’s one of the best for screen calibration)?
-Do I need a diffuser?
-If I need one what can I use to make one?



Thanks a lot for your help

Damien

[Citation4444]

Screens generally act as excellent diffusers making a diffuser on the meter superfluous. I don't know the characteristics of your screen surface, so can't advise except to say I believe the method of maximizing the meter's Y reading should work best. If your screen is retroreflective with high gain, it could make placing the meter tricky in order to avoid its shadow.

Also, how far from the screen are you placing your meter? I find 10-12 inches works well.

If you can't do it this way and want to face the projector, a diffuser is definitely required. Especially in your case, since you have a very short throw and the angle between thr R and B crt face is large. Since these meters accept light with a definite cone pattern, without a diffuser they have a rather narrow beam of acceptance.

SpectrCal recommends a diffuser for the meters they sell, so you might look at their site, or ask around here. Compensating your results to account for the diffuser is not easy, and they are not color neutral, so this greatly complicates things. This is another reason it is better to calibrate using reflected light from your screen with your meter facing the screen.

Finally, your meter DTP-94 is generally highly regarded. Since they haven't made these in quite a while, yours might not have aged gracefully but since you've been using it calibrate other displays it's probably ok.

I'm afraid I haven't been of much help.......as it appears you were doing correctly.

Bob