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Photoshop CS6 RAW Conversion
Photographers shooting raw files need to convert them to TIF or JPEG for best quality (in-camera JPEG is low quality in virtually all digital cameras).
Conversion using Adobe Camera Raw in Photoshop CS6 13.0.3.
Nikon D800E 14-bit RAW to 16-bit TIF uncompressed
The Mac Pro easily outpaces the iMac here, and surprisingly even the MacBook Pro with Retina display 2.7 GHz does so also.
These results were double-checked for the iMac including using the OWC Mercury Accelsior+ Helios to verify that I/O speed wasn’t the cause (a 7 second improvement was seen, e.g., 342 seconds).
Observation of CPU usage suggests that the extra cores of the Mac Pro systems was a factor here.
Nikon D800E 14-bit RAW to max-quality JPEG
The iMac is about the same speed as the MBP Retina, faster than the 6-core Mac Pro, but slightly slower than the 12-core.