I just installed 13.0.3 upgrade for 64 bit and now when I resize an image to, say 800 x 600 pixels, the resulting image is very small. To get the image to display in the window at the same size (100%) as before the upgrade I have to zoom to 200 - 300%, and get the associated pixelation. Nothing else on the computer has changed (i.e., display preferences) to my knowledge. I am using a rMBP running OS X 10.8.2. Very frustrating because this is a change in behavior after the upgrade. The screen shot below shows what 100% zoom looks like now, which is about 1/3 the size an image like this used to be prior to the upgrade.
You're on a retina-equipped Mac. The change was done on purpose, to fully support your high density display.
Now when you view images at 100% zoom, it literally is using each pixel of your display to show one pixel from your image.
Earlier Photoshop versions were running in pixel-doubling mode - using 4 pixels (2 by 2) on your display to show one pixel in your image at 100% zoom.
If you want to view it as it was before, try 200% zoom.
I haven't personally seen a Mac with a Retina display run an application in pixel-doubling mode. It sounds as if it may do more than simple digital duplication of pixels, but rather some kind of interpolation, which would look smoother.
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