What JPEG export quality should I use in Lightroom to preserve the original quality?
Asked 12/31/2019
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I’m editing JPEG photos from a Samsung Galaxy S9 in Lightroom CC, not RAW files. After making adjustments and exporting, I want to avoid adding visible artifacts or making the file much larger than the original. What Lightroom JPEG export quality setting should I use to best preserve the original image quality? I noticed that exporting at Quality 100 can make the file larger, even when the edit is only a crop.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
2
You can't
In order to apply any modifications to a JPG file, it needs to be fully decoded into plain image data first(1) - in memory the data is much bigger, as it's necessary to store all RGB-Bytes directly. If you save the modified image it's just like doing a completely new JPG compression on the data. This will cause additional artifacts. Since this new compression step has it's own parameters, a file size increase comparing to the original can very likely occur.
The only thing you can do other than adjusting the settings by trial-and-error is to use the file size parameter during export to define an upper bound for the image size.
(1) There are some possibilites to loslessly rotate or crop a JPG, but this most likely doesn't apply for this answer.
Originally by user26144. Source · Licensed CC BY-SA 4.0
user26144
6y ago
0
Generated from our catalog & community — verify before relying on it.
There isn’t a Lightroom export setting that will preserve the exact original JPEG quality.
Once you edit a JPEG, Lightroom must fully decode it to image data and then create a new JPEG when you export. That means the file is compressed again, so some additional loss is unavoidable. The new file may also be larger or smaller than the original because JPEG size depends on the encoder settings and image content, not just pixel dimensions.
So:
- Exporting at Quality 100 does not mean “same as original.”
- A larger exported file does not necessarily mean better visible quality.
- A crop can still produce a larger file if the new compression is less aggressive than the phone’s original JPEG.
If your goal is to minimize extra JPEG damage, use a high-quality export setting and judge the result visually. If your goal is to control file size, use Lightroom’s file size limit option.
Only certain operations such as some lossless JPEG crops/rotations can avoid recompression, and that generally does not apply to normal Lightroom editing/export.
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