100% view

[KevinA]

I just realised that viewing at 100% in Aperture or Preview is half the size on screen of a 100% view in Photoshop. I've checked settings are the same, pixel dimensions etc. I'm puzzled by this both programs say viewing is 100%, but to match on screen size I either downsize the P/shop view to 50% or up the Aperture view to 200%. I can't see any defaults in either program to adjust.
Any ideas?

[Whitney Dunn]

Are you on a Retina MacBook Pro? What's happening sounds very much like the difference between retina optimized applications like Aperture 3.3 and later and non-optimized ones like Photoshop 13.0 and earlier. Retina optimized apps show true 100% display -- pixel for pixel -- while non-optmized ones pixel double -- 1 to 4 counting the horizontal and vertical doubling. If you're on CS5 or haven't updated CS6 since December 2012, when Photoshop got retina support, that's likely what's happening.

[KevinA]

Thank you that will be it then.