Confused about Gamma!

Hi,

There's must be something here I'm not quite getting - can anyone shed any light on this weirdness?

I don't have a proper profile for my monitor, so I'm currently using the sRGB Color Space Profile as a generic profile.

This specifies a gamma of 2.2, yes?

So if my monitor is adjusted to have a gamma of 2.2, the sRGB profile should characterise it reasonably well, yes?

According to the testcharts on this page: http://www.normankoren.com/makingfineprints1B.html
My monitor's gamma is a fairly accurate 2.2, and according to this page: http://www.photoscientia.co.uk/Gamma.htm
both the black level and gamma are about right - once again, gamma 2.2.

I have a profiled scanner and printer, and if I do an Absolute Colorimetric transform of the scanned IT8.7 target from the scanner to printer profile, and print the result, a side-by-side comparison of the print and original yields a very close match.

Now what I don't understand is that if I do an absolute colorimetric transform of a scanned IT8 target from the scanner's profile to sRGB and view it on screen, the result is too light.
Furthermore, if I do a transform of any kind from screen (sRGB) to a printer profile, the result is too dark.

If instead of using the sRGB profile, I use a virtual profile with sRGB's primaries but a gamma of about 1.8 (without touching the monitor's settings - the web-pages still indicate 2.2) then transforming both from scanner to screen and screen to printer result in a much closer match.

So what is my screen's Gamma? 1.8 or 2.2?

If 1.8, why do the test-charts mis-identify it?

If 2.2, why does the monitor's behaviour not seem to match that value in practice!

Can anyone put me straight here?

All the best,
--
Alastair M. Robinson
.

Relevant Pages

  • Re: color space of a scanned image
    ... With a color profile you are probably getting sRGB from the scanner. ... didn't say sRGB from JPEG, because I don't know how your JPEG decoder ...
    (sci.image.processing)
  • Re: Profiles and gamuts
    ... I'm still knew at all this but am I correct in saying that "scanner ... profile" is basically my capture device's output? ... When I compare that to sRGB (with sRGB as ...
    (comp.graphics.apps.photoshop)
  • Re: Scanner profiling with Nikonscan 4.0.2
    ... -the Nikon CMS will always apply a low-level profile e.g. ... the scanner self calibrated, it does not impact on hue and saturation. ... Gamma is set once and for good, and while determine best use of bits ... My computer system apparently uses 2.0 for its gamma. ...
    (comp.periphs.scanners)
  • Re: Scanner Profiling: Critical or Luxury?
    ... Often in the *opposite* direction of the profile change! ... degraded by having a scanner profile applied in the wrong direction. ... Profile + correction = 2 edits. ... Take an easier example than color correction: gamma. ...
    (comp.periphs.scanners)
  • Re: 1905FP Brightness Solution/Fix...
    ... comes to gamma and brightness. ... and load the 1905FP.icm profile. ... Go into the monitor's OSD menu and make sure the Brightness is ... eye blistering brightness. ...
    (alt.sys.pc-clone.dell)