JPG default export quality

[Ritergeek]

Is there a way to set the default value for jpg exports to 100%? Right now it's 90% and I always save at 100%. I've looked through the export settings in Preferences and see only Export File Type but nothing about quality.

[zeuspaul]

Save defaults in the jpg export screen.

[Ofnuts]

(11-29-2023, 10:41 PM)Ritergeek Wrote: Is there a way to set the default value for jpg exports to 100%? Right now it's 90% and I always save at 100%. I've looked through the export settings in Preferences and see only Export File Type but nothing about quality.

In JPEG export dialog you can set the quality and save the settings as defaults, and reload your defaults if necessary.

   

I draw your attention on chroma sub-sampling, because if you didn't set it to 4:4:4 some of your color information is binned, even at 100% quality.

Otherwise, 100% quality JPEG serves little purpose, because it is not lossless. The encoder still does a lot of computations to represent a 8x8 square as a Discrete Cosine Transform and when your reload the decoder does some more, so there are round-off errors. So even if you don't get the rounding/binning of lower quality settings, you don't get the exact same values out. On a test 15Mpx image, exported as 100%, 4:4:4, FP DCT Jpeg, and reloaded as a new layer and compared to the original image, in each R/G/B color channel 5M pixels had a different value from the original, and since this doesn't happen on the same pixels, at least 10M pixels (two thirds...) are different from the original (different in the "Value" histogram).

If you want lossless, use PNG or TIFF. Here is a size comparison (in K) of the various PNG and lossless TIFF options, together with the JPEG with all options at full throttle:

14092   TestPicture-100%.jpg
20180   TestPicture-Deflate.tif
22828   TestPicture-LZW.tif
59256   TestPicture-PackBits.tif
20944   TestPicture.png

The similarity of PNG and TIF-Deflate isn't a coincidence, PNG also uses the Deflate compression algorithm.

[PixLab]

Except for experimental purposes, never go above about Quality 95
Using Quality 100 will produce a file two or three times as large as Quality 95, but of hardly any better quality.
Quality 100 is a mathematical limit rather than a useful setting, it is not a percentage....

If you see a file made with Quality 100, it's a pretty sure sign that the maker didn't know what he/she was doing.

Source > http://www.faqs.org/faqs/jpeg-faq/part1/section-5.html