How to avoid reprocessing of images by ckfinder?

Question

I'm running an installation of fork-cms which includes ckfinder which is part of the ckeditor. When I upload images they often come back with much larger filesizes as the uploaded ones which indicates any reprocessing done to them and not checked the resulting filesize!

Example: photo optimized end created by photoshop 1280x960 @ 50% quality -> approx 400k uploaded to the server comes back same dimensions but over 800k in size. When trying to reproduce the quality settings in PS results in approx. 80 to 85% quality.

I turned of imageprocessing for images of larger dimensions which are were set to 1600x1200 by setting them to 0x0.