Message
Re: [colorvision_group] dark monitor after calibration with spyder2pro...
2007-06-21 by CDTobie@aol.com
In a message dated 6/21/07 2:23:23 PM, markshaxted@... writes:
I've just got a spyder2pro monitor calibrator, and I'm dissapointed
with the results. Using the manufacturers profile (HP f1903 19" LCD
monitor) the colours are 'fairly' accurate, and I can clearly make
out all the shades from the following page (just as a common
reference)
http://www.cambridgeincolour.com/viewing.htm
However, after calibrating, and using a McBeth colour chart (24
patch) to guage against, the colours on screen are MUCH darker (at
least a stop), and I can only differentiate that lightest dark shade
from the above website.
I get good distinction of all near whites and near blacks from this page with a Spyder2PPRO calibration...
If I increase the brightness (backlight) &
contrast to maximum after calibration, I get much closer colours, but
still cannot see the darker shades - however, surely this negates the
point of calibration.
Adjusting these after the fact is not the solution, but what settings and adjustments you choose during calibration can still cause different results.
Calibration settings I'm using are 6500K, gamma 2.2. The best results
are also after calibration in the morning when the sun is not visible
from the window to the room I'm in. This makes sense as I'm using
natural ambient daylight.
I'm also using a jpg from the Dry Creek website of a ColourChecker
chart, with the patches altered to the correct sRGB values as
documented with the physical colour chart. In theory I should be able
to compare the chart against the screen, and the two should be
identical. They're not unless, as stated above, I bump up the
brightness & contrast to max on my monitor. Either way though, I
cannot see the darker shades.
Contrast on an LCD is rather a hack, there is not physical contrast control... its messing with the video curves, which we have carefully set in advance, so you don't want to mess with them later. Brightness is not usually an actual brightness control on LCDs, its a backlight, so check it as such in Spyder2PRO. Then use the Ambient LIght option, and the measured B&W Luminance options. Then you leave the black blank, and fill in the white with what the ambient light option suggests, to get a reasonable ambient light to monitor brightness ratio.
I get slighter better dark greyscale results if I go to 1.8 gamma,
6500K, but the colours are not as accurate.
Gamma is corrected for in color managed applications. If I calibrate one monitor to 1.8, and a second beside it to 2.2, and view the same image on each, the shadow detail is identical, except for the few levels I loose to the heavier gamma correction in the 1.8 profile. If you are seeing differing results, you are doing something wrong, or using a noncolor managed application (such as PC webbrowser...)
Does anyone have any ideas as to how I can improve on the results I'm
getting? I cannot see anything wrong with what I'm doing
You haven't told us what you are doing, what settings, what process, what applications, what platform etc...
- and trying
to calibrate in a dark room actually makes things far worse.
A bright LCD in a dark room is indeed a poor choice; the ambient light tool would assist you in avoiding that...
C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com
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