Pictures look different in OpenGL/non-OpenGL mode

SK
Posted By
Stefan_Klein
Dec 26, 2008
Views
357
Replies
6
Status
Closed
I made a test:
-turn OpenGL on
-Make an "empty" sRGB picture (or any other RGB) (lets call the picture "testpic").
-make a black/white gradient across the whole picture.
-make a screenshot (lets call it "A" and save it) -close pictures
-turn off OpenGL
-open "testpic"
-make a screenshot (lets call it "B" and save it) -close pictures and turn OGL on or off (doesn`t matter)

-now open "A" and "B" and put them into one picture (as layer1 and layer2) -put layer2 in "difference"- mode

What you see should be totally black, because there should not be any difference between "A" and "B", because it`s a screenshot of one and the
same file. But I DO NOT see only black. There ARE differences!

So here we have another OpenGL problem: One and the same file looks different when displayed with or without OpenGL!

Geforce8600GT/512MB with latest driver / Vista32bit
Related Tags
difference look mode opengl picture

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SK
Stefan_Klein
Dec 27, 2008
Can anyone else try that experiment? I mean it`s very discouriging to see that Photoshop displays pictures different with OpenGL on and OpenGL off.
P
PECourtejoie
Dec 27, 2008
"Photoshop displays pictures …"

Videocards displays pictures…
RK
Rob_Keijzer
Dec 27, 2008
Videocards displays pictures…

<Stage Manager> Psst! Pierre!! Come back! I gave you the wrong text! Those are Adobe’s lines! Here
Rob
RK
Rob_Keijzer
Dec 27, 2008
But seriously, I’ll try the difference blending mode trick later on.

Rob
MV
Mathias_Vejerslev
Dec 27, 2008
Are you taking the screenshot at 100% magnification? Also, taking a screenshot of an adobeRGB photo, will give you an sRGB conversion of same.

The OpenGL version will be anti-aliased, the non-openGL will not be anti-alisaed. You don’t need to make screenshots to appreciate this difference.
SK
Stefan_Klein
Dec 27, 2008
Mathias,

good point about sRGB! I did it in sRGB and also at 100%. And if I take a close look at the gradients and the difference between OGL and non-OGL, it`s clear that the difference is not in the antialiasing, but simply that some shades of gray are lighter or darker than in the other version.

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