Questions about raw, tiff, jpeg, and DNG

Started Mar 27, 2013 | Questions thread
Hugowolf Forum Pro • Posts: 12,674
Re: Questions about raw, tiff, jpeg, and DNG

Tom Axford wrote:

JPEG images incur a loss of information every time a JPEG is saved.

This is a myth, and can easily be shown to be incorrect. If you an edit between saves, even a minor one pixel edit, then you can incur data losses at each save, but simply saving the file using the same compression and resolution parameters should not cause further data loss.

It is an easy, but tedious, test to do. And since I have seen the results before, I am not going to repeat it.

Take an image and open it in Photoshop. Save it as a Jpeg with whatever parameters you like. Make a duplicate of the image and save it with the same parameters, then hit ctrl+shift+S (save as, then enter, enter, enter) a million times. Copy the millionaire duplicate onto the original as a layer and change the blending mode to difference. There should be no difference.

Brian A

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