CurtPalme.com Home Theater Forum

[Helloweein]

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Hi all and especially a big THX to Kal for your guide!
I have a Benq 8700+ projector ( 300 hour ) in a room with no light control ( white concrete wall ).
After reading your guide I have calibrated Benq greyscale with the Eye One and HCFR software. My score is near perfect:
6500K
gamma 2,2 - 2,35
from 20 to 90IRE scale I get less then delta E 3
just on 10 and 100 IRE I get delta E of 9, if IRE 0 doesn't count
But my real problem is the illuminance. My Eye One reads 12,50 cd/m at best. Even if I go up with the contrast till completely ruin the picture the illuminanc don't change very much.

I would like to know if the fault for this is my white room, would I solve this problem if I paint the wall to dark blue, or is
the problem for this elswere?
I hope that this is not a stupid question, I've been in a cinema before but not everyone can set up the projector in a light controlled room.

Thx in advance
Cheers

[David_Web]

The reason digitals are so bright on paper is that the colors are way wrong. Blue is way to bright etc.
So when you calibrate it the luminance will be way lower. And so will contrast. IIRC I read somewhere that the light output almost is cut in half when properly set up. If you search a little you will probably find an article that mentions this with measured numbers.
Not sure if this is your problem but I would guess so.

[Helloweein]

THx David!

I'm wondering if exist a formula that corelates the reading of luminance of a projector with the color of the room?
In this way:
if the luminance from a screen with a calibrated projector in a totaly black treated dark room is 14ftl, what amount of ftl will a colorimeter read from the same screen in a totaly white room!?

Cheers

[David_Web]

Same.
Well it might be a little brighter but not much. I don't think it differs that many %. The difference in contrast will be huge though.

If you really want to know you can shift the projector slightly and take a reading from the now dark part of the screen and then subtract that from the full white reading.
Or you can compromise by creating a dark square on the middle. Ether digitally or just blocking the light from around 1m so it doesn't shadow the rest of the room.
Further you could subtract the reading from a dark projector to get rid of the ambient light.

Now the perceived luminance could be way off from the measured. And usually is.

Not sure if that answers your question or not.