Re: Gray Gamma 2.2 space and Photoshop2022 (23.1.1)
Re: Gray Gamma 2.2 space and Photoshop2022 (23.1.1)
- Subject: Re: Gray Gamma 2.2 space and Photoshop2022 (23.1.1)
- From: Scott Martin via colorsync-users <email@hidden>
- Date: Sat, 12 Feb 2022 23:55:06 -0600
Peter, you didn’t tell us much about how your file was made but I think we can
replicate what you’re seeing.
In Photoshop 2022 goto the Color Settings and set the RGB Working Space to sRGB
and the intent to RelCol. Create a new Grey Gamma 2.2 document and fill in a
portion of the image with 5,5,5 and 10,10,10 etc as chosen in the Color Picker.
[By the way it’s a bit weird to be choosing RGB values for a grayscale image].
Save this file. There’s no need to convert it - instead look at the info
palette with one section set to RGB. It will show you the 5,5,5 and 10,10,10
values you’re expecting to see.
Now goto the Color Settings and set the RGB Working Space to AdobeRGB. Take
another look at the Info palette and you’ll see that the values are now
13,13,13 and 18,18,18.
Now open this same file in any older version of Photoshop and repeat this test.
You’ll find that it’s the same. Photoshop is consistent on this.
sRGB and AdobeRGB don’t actually share the same 2.2 gamma curve. sRGB modifies
the gamma 2.2 black approach with a linear segment, and that’s what we're
seeing in this test. Goto https://en.wikipedia.org/wiki/Adobe_RGB_color_space
<https://en.wikipedia.org/wiki/Adobe_RGB_color_space> and
https://en.wikipedia.org/wiki/SRGB <https://en.wikipedia.org/wiki/SRGB> and
search for “gamma” if you’d like to read up o this.
The curious thing to me is why you’re seeing something different in PS2019.
Check your Color Settings as there’s likely a discrepancy there. Cheers
_____
As a side note I wish we could see Lab values to two decimals points. And I
wish the Color Picker and Info palette were updated to clearly specify what
color spaces and intents are being used.
Scott Martin
www.on-sight.com
Imaging Science for Art
> On Feb 12, 2022, at 8:31 PM, Peter Miles via colorsync-users
> <email@hidden> wrote:
>
> Hi List members
>
> Adobe RGB (1998) is gamma 2.2. So I was surprised to see that Photoshop (2022
> 23.1.1) changed the RGB values of a step-wedge I made in Gray Gamma 2.2 space
> after I converted it into Adobe RGB space. For example, in Gray Gamma 2.2
> space my wedge starts out with RGB values, 0,0,0 / 5,5,5 / 10,10,10 /
> 15,15,15 / 20,20,20…. and the AdobeRGB(1998) conversion goes 0,0,0 /
> 13,13,13 / 18,18,18 / 22,22,22 / 27,27,27…
>
>
>
> Hmm…
>
> I just tried the same thing in Photoshop2019 and the RGB numbers stay the
> same for the conversion from GG2.2 to adobeRGB(1998) and back again.
>
> There are some other weird things happing with Photoshop 2022 handling of
> Gray Gamma 2.2 space black point.
>
> If I use a levels layer and lift the black point output level, I have to
> lift it to 5 before an eye dropper on my image on full black patch, finally
> moves from 0 to 1. That’s not right.
>
>
>
> REQUEST
>
> Can someone else on the list check this out. And let me know if you are
> seeing the same behaviour?
>
> Maybe there is something broken with our particular install?
>
>
>
> I am going to stop using Photoshop 2022 with my GrayGamma 2.2 space images
> till I can get to the bottom of this.
>
>
>
> Regards
> Peter Miles
>
>
> _______________________________________________
> Do not post admin requests to the list. They will be ignored.
> colorsync-users mailing list (email@hidden)
> Help/Unsubscribe/Update your Subscription:
>
> This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden