Azmarul Islam - Blogger

By Author: johnny
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Gamma Differences
Windows has used a gamma of 2.2 since its introduction. OS X has used a gamma of 1.8 for all versions except Snow Leopard (the latest release), which uses 2.2. What does this mean? Prior to Snow Leopard, Web pages looked darker on Windows. Thankfully, both operating systems are now in sync, so a Web page should look very similar on a Mac and PC that use the same monitor.
Information about the iPhone’s gamma is a little hard to come by; I couldn’t ascertain whether it is 1.8 or 2.2. This is another reason to test your interface on an iPhone.
Difference Between “Assign Profile” And “Convert To Profile” Link
Now would be a good time to mention the difference between Assign Profile and Convert to Profile, so that you know which to use when.
Each Photoshop document contains a color profile that’s separate from the actual color data stored for each pixel. Assign Profile simply changes the profile in the document, without affecting any of the color data. It’s a non-destructive action: you can assign a new color profile to your documents as often as you like without doing ...
... any damage. Assigning a new profile may change the way your document appears on screen, but the data contained in the file will remain unaltered.
Convert to Profile is quite different. Not only does it assign a color profile to the document, but it tries to keep your image looking the same on screen. It does this by processing the color data contained in the file for each pixel. Converting to a new profile will more likely preserve a document’s color on screen, but the data contained in the file will be permanently altered. Use with caution.
If you’re copying layers from one Photoshop document to another, you will want to ensure that the documents have been assigned the same color profile.