Gamma Confusion

Started 2 months ago | Discussions thread
Sailor Blue
Sailor Blue Forum Pro • Posts: 15,327
Re: Gamma Confusion

pixelgenius wrote:

Sailor Blue wrote:

pixelgenius wrote:

Gerry Pasternack wrote:

My primary goal in monitor calibration is to achieve best image viewing. I do little image printing. My editing/viewing software is all color managed.

My software calibration choices for gamma are a number (like 2.2), L*, or sRGB. (There is no "Native Gamma" option). Which gamma setting is best?

Again there's not really a "best" but 2.2 should be just fine.

Based on viewing test photos it seem that Gamma=2.2 setting produces an excellent image. I'm just wondering why tests for gamma measurement (Ezio, Lagom) shows that the gamma for my calibrated monitor is closer the 1.4 than 2.2. Wondering why that is.

A gamma value of 2.2 is the correct value for aRGB, and very close to the correct value for sRGB.

The gamma value of a display and the gamma value of working space is completely agnostic and separate! sRGB in fact has no Gamma curve (it has a TRC)

The correct gamma for sRGB is very close to 2.2 although it is best matched using “sGray” in newer versions of Photoshop.

As I said, a gamma of 2.2 is the safe choice unless you are working exclusively in the ProPhoto color space.

Gamma 1.8 is a better choice if you work exclusively in the ProPhoto color space.

Wong! Doesn't matter whatsoever.

Actually it makes a big difference if you are doing things like dodging and burning or exposure blending.

When working in the ProPhoto color space using a gamma of 2.2 can result in a 50% or larger increase in the area selected by a luminosity mask.

With dodging and burning using the wrong gamma in the ProPhoto color space can result in the effect being applied in areas that should be protected by a selection or mask, and the more often you paint outside the protected area the more the effect builds up.

Using a gamma of 1.8 with aRGB or sRGB image can result in a decrease in the area selected by a luminosity mask.

A gamma value of 2.2 is the safe choice and should probably be used unless you work exclusively in the ProPhoto color space.

Wrong! ANY gamma value used for calibration will work with ProPhoto RGB and all other RGB working spaces in color managed applications.

Wrong again. It effects the gray working space, which in turn effects how dodging and burning and luminosity masks work.

Being honest I just found this out myself and have always assumed what you said was correct. Now that I know better I am willing to change, are you?

Greg Benz - How to optimize your "gray working space" for better luminosity masks

Note that if you choose the ProPhoto color space and a Gamma of 1.8 in Photoshop's Color Settings the gamma setting will be wrong if you import a sRGB JPG image. You have to change the gamma again in Color Settings to get the correct display for the sRGB JPG.

Utterly ridiculous. There's no import into Photoshop. You can use a gamma of 1.8 for the display and use ProPhoto RGB or any other RGB working space without any issues whatsoever in Photoshop.

Call it Open or call it Import. They mean the same thing - bringing an image into PS for editing.

The important point was that the gamma setting effects the gray working space and is sticky until you change it.

Please learn how this actually works before further writings:

https://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf

The gamma of the display being calibrated has absolutely nothing to do with the gamma within an RGB working space! Nothing. They simply share the term 'gamma'. While some of the RGB working spaces don't even have a gamma curve.

What brought this up? It doesn't relate to anything I said.

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