File growth? Aperture export to folder, then import to Photos, then export back to folder.


macrumors regular
Original poster
Sep 1, 2010
I am switching over to Photos. I'm exporting from Aperture into the pictures folder, then importuning to Photos, then back to the pictures folder. I'm exporting JPEGs at maximum quality. The Aperture exports are around 4MB, but the Photos exports are around 10MB. Why is the file size increasing?


macrumors 6502a
Jan 4, 2015
Key West FL
There are several possibilities:

1. "Maximum quality" is not the same from program to program. It is possible that the newer Photos' max quality uses less compression than the antique Aperture's max quality.

2. Any and all compression artifacts, now matter how subtle, will have a negative impact on any future JPEG recompression. It's possible that Photos is not copying out the old imported JPEG, but is instead generating a new JPEG when exporting. This is definitely the case if you do anything to the JPEG in Photos. The newly generated JPEG will not compress as efficiently, even if it uses exactly the same compression technique, since it has to deal with the added detail that is the artifacts left by Aperture's compression and it will be adding its own new artifacts in the process.

The last point in #2, above, is the biggest reason that using JPEG as the format for your "master" files is such a bad thing.
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