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Typically internet browsers and general image viewers like AcDsee or Lview Pro have null (no) gamma correction
built in so when viewed through one of these programs an image will look as it would to the rest of the world, if there are
no other "system" corrections, which is what 80% of all others will see. but if your video board or system has gamma
correction and it is not set proper then what you percieve as your "just made work of art" might look less than that
to others. If you fall into this group then you need to disable all gamma correction before monitor adjustment. If there
are several interacting variable Gamma functions affecting the way an Image is produced or percieved then we need to
break the system down into the individual parts, in the correct order, and adjust them Singly. The order would be Monitor,
System, Video board and last but not least Graphics program. Your system does have the first, may have the second
and/or third and probably has the forth but they must be isolated.
Perform this procedure to setup your monitor, then go through the calibration / gamma procedure on your
system/video/graphics program in an isolated fashion and that order, using the above image to reference to without
retouching your monitor adjustment. If your gamma correction is in an image editing program or is system level where
it would recalculate the gamma of an image then the latter procedure would involve just loading this image and then
saving it, under a different name so as not to corrupt the original, and verifying that the image levels have not
changed any appreciable amount beyond the original. High end computers like Sun or SGI have, inherent in their OS,
a system gamma function yet when an image created on the Iris is viewed on the Sun, Mac or PC the image is much too dark,
conversely when created on the Sun and viewed on the Iris it is washed out. Paul Haberti has a page on this anomoly
Here however he has not defined whether the aberation is
caused by monitor misadjustment or an incorrect gamma function inherent in a system. In a week or two I will be back
to an SGI indy and I will check out the problem then.
In the pluge area, Ire
and blacker than black have no meaning in CG yet we need a similar function so I have placed a graduated gray scale from
81% to 99% K (black) in RGB steps of 4 out of 256. In addition I placed a dual set of dots, surrounding the scale and signifying
the proper Black level (brightness) adjustment, which is total diminishment by that horizontal point of 93% black (16 RGB). My
intent was to show one end of this bar bright enough for those that have monitors so far out of adjustment, to notice it, yet
retain a resonably fine step. I also added a linear grayscale for at-a-glance gamma linarity ie: evenness through out the spectrum.
Charles Poynton's adjustment procedure He is
the Rocket Scientist in regards to Gamma and Colour, Other pages on his site do get a little deep however he wrote the FAQs.
A monitor is properly adjusted when it meets two conditions. First, black should produce true black, to help maximize
contrast. Second, white should produce the desired / proper intensity.
Picture level / Contrast and
Black level / Brightness.
There exist standards for video (NTSC, PAL, SECAM) calibration techniques however there is
a strong differention between video and desktop graphics calibration requirements. There are also several standards for
Color Bars - EIA, SMPTE, EBU, IBA, and BBC are the most dominant. Of these they have variations in Saturation and
Amplitude which we wont go into here, what we are concerned with is the fact that color bars were designed to exploit
the deficiencies of Video / Television transmission.
Typical modern color bars have 3 main parts to them, The main color
bars, The duo toned blue areas (-I and +Q) with white between them in the lower left and the Pluge in the lower right.
In video usage the transition between certain adjacent colors produces various anomolys such as dot crawl caused by NTSC
interlacing or null (undefined color) areas because it takes up to the recipricol of the burst frequency, in time, for
the next color to become valid, scanning from left to right. The dual blue areas were defined for a previously used and
superior modulation technique that has been almost universally replaced by Y, R-Y, B-Y which is basically the same except
for a slight equation and phase difference. They along with the Color of the main bars are used to set the Phase (Hue).
Finally the Pluge area is there for Monitor level adjustment. Standard Pluge bars (3 small verticle bars) are grayscale bars
at black -4 Ire, Black and Black +4 Ire.