Today’s Question: I need to edit some JPEG files provided by a client and return modified JPEG files. I know that generally every time you save a JPEG it incurs some slight degradation. Is there any combination of Adobe Camera Raw/Lightroom Classic Develop followed by Photoshop editing that would not incur this degradation or would have the least degradation?
Tim’s Quick Answer: My recommendation is to minimize the amount of editing that is done while the images are in the JPEG format. In other words, I would convert to a different format and only save again as JPEG when you’re completely finished and ready to deliver the files to the client.
More Detail: The first thing I would do is see if the source images are available in something other than JPEG files. If the images were captured as JPEG images in the first place, then you should just obtain the JPEG images that have not been edited by the client. But if they were captured in a different format or scanned from slides or negatives, I would get the original images rather than JPEG copies.
If the images are only available as JPEG images, I suggest converting to another file format first to avoid the potential for cumulative degradation caused by JPEG compression. To be fair, this degradation is minimal, and only occurs when you have modified the image and then re-saved the result as a JPEG. That’s because when the pixel values have changed the image must be rendered again with the JPEG compression applied, which degrades image quality to some extent.
If you’re working in Lightroom Classic you can select the JPEG images and choose Photo > Edit In > Edit in Photoshop from the menu. In the dialog that appears, choose “Edit a Copy” and click the Edit button. This will open the image in Photoshop, creating a derivative TIFF or PSD file based on the current setting in Preferences. You can then perform all the work in Photoshop, preferably with a non-destructive workflow such as by using adjustment layers and additional image layers. When you’re finished, simply choose File > Save from the menu (not Save As or Save a Copy) and then close the image. You can export the result from Lightroom Classic as a JPEG to deliver to the client.
If you’re working directly in Photoshop you can simply open the JPEG images, and immediately use the File > Save As command to save them as a TIFF or PSD file. Once again I would suggest working non-destructively, and then save the updated image with layers intact. You can then use the File > Save a Copy command to save an additional copy of each image as a JPEG for the client.
The main thing to avoid in this context is to continually be updating the pixel values for a JPEG image and then saving the updates along the way, causing the compression to be applied to the image multiple times. Again, this degradation is very minimal in general, but I still consider it a best practice to work on images in a format other than JPEG to avoid the degradation and help ensure maximum image quality.