Message
Re: [colorvision_group] Re: Projector Calibration? Waste of time!
2006-07-05 by CDTobie@aol.com
In a message dated 7/5/06 2:01:46 PM, martin@... writes:
First of all, the PLV-70 is a high brightness unit (2000 Ansi Lumens),
so when it projects a white image, the whole room is not dark at all
anymore. The screen reflects so much light, that you can easily read a
newspaper in the room. That's why you can also tell if the white is
greenish, blueish or whatever.
No, that defies the laws of color theory; if you fill a room with yellow light, the eye adapts, and that yellow light looks white. There must be some other source before your eye can distinguish.
So in my opinion, I would make sense to
calibrate the white point - at least you could give the users the
possibility to do so if they wish.
They have that option via the LCD mode, though color science says otherwise.
Secondly, my Spyder2Pro hardware seems to be ok - I've successfully
calibrated 4 monitors with it and the results are very good.
Thats good to hear.
I always
liked the "After" picture much better than the "Before" one - flesh
tones looked more natural and the overal image appearance was more
pleasing. So "my Toyota is not broken", I should just not try to drive
it somewhere where it's not supposed to be ;-)
How would you explain the many satisfied projection S2P calibration users then?
I guess the whole projector calibration process is somehow strange.
Definately very different than monitor calibration. For instance: ambient light in the room does not define how black your monitor blacks are, but it does for projection screen blacks. Another reason you need a dark environment for projection. Is the room you are working in pitch black when the projector is off?
I
can't imagine getting reliable results when the sensor reads light
from its own shadow.
Another color science point you are missing. Projector calibration is relative. (If you move the projector a couple more feet from the screen, to total luminance at the screen will be much lower, but you can calibrate for either condition, and the eye will adapt to see both as being the same, since the brightest object will define white, as well as defining the color of white.) So having the Spyder's own shadow on the screen simply reduces total luminance by a few percent, as it would if you moved the projector a bit further back. The light that does hit the screen has the same characteristics with or without that shadow, and the Spyder is reading the whole screen, not some tiny area in the shadow.
And my experience seems to prove that point. The
procedure as suggested by the calibration software is easy to follow
and you can't really do anything wrong.
We'll never know, if you don't go through the support process... but your results would indicate something is wrong, whether with the product, or your process, or the situation.
So if it still produces
results that are way off (and the hardware is ok), then either the
software must be buggy or the whole principle of the calibration
process has flaws.
So far I am seeing several flaws, but they are in your logic. Again: many technically expert people have run this, reviewed it, loved it. Are they somehow all wrong, and your single case is the only right one?
I guess it's the latter, otherwise I couldn't
explain why my calibration works for monitors but not for projectors.
Another flaw in your logic: there are other explantions you don't consider here. For instance: I can envision your results if there is significant ambient light in the room that is not coming from the projector: that would violate projection rules, and not allow the eye to white point compensate to the projected light.
C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com