jpg Compression [Does LR re-compress a JPG when it is edited and saved?]

[rcroon]

When editing a jpg and then re-saving it, some applications do the compression all over again resulting in a loss of data.

I was told that Photoshop (recent editions) do not recompress a jpg after editing.

I have not been able to find out if Lightroom CC -Desktop edition recompresses a jpg when it is edited and then saved.

Anyone have info on this?

Does anyone convert their jpg's to tif or DNG (or something else) before doing any work in order to avoid this?

[JP Hess · Accepted solution]

Making adjustments to JPEG images in Lightroom doesn't do anything to the original JPEG. Those adjustments are simply stored in the catalog, absolutely nothing is done to the original file. The only time you will have a new JPEG with compression is if you export a new copy, and that copy will be affected by compression. But it would take several iterations before you would be able to detect any image deterioration, especially if you use a high quality setting. Saving the image as a TIF or PSD could probably help reduce the risk of image deterioration. Converting to DNG would probably do that as well.

[rcroon]

You are right!    I completely forgot about the catalog holding the corrections.  DUH.........

Thanks