Hi,
When JPEG compression is carried out, there can be small colour changes - JPEG compression carries some significant disadvantages, this is one of them.
As D. Fosse wrote Jpeg compression is ALL about minimising filesize.
Interesting info here: http://learnmem.cshlp.org/site/misc/tsg_JPEG_instructions.pdf
"JPEG compression attempts to create patterns in the color values in order to reduce the amount of data that needs to be recorded, thereby reducing the file size. In order to create these patterns, some color values are approximated to match those of nearby pixels."
Inadvisability of resizing a JPEG image after compression, due to increasing visibility of JPEG artifacts, is another intrinsic loss that many people discover after it's too late.
To give an idea of losses involved - author of Photoshop For Photographers, Martin Evening [https://www.martinevening.com/index] wrote that having a RAW original has a significant advantage over a JPEG. since allowing a camera to make a Jpeg discards up to 83%, 83%! of image data. I don't expect, though, that the loss from compressing a Tif or PSD to Jpeg is quite as severe.
I hope this helps
if so, please "like" my reply
neil barstow, colourmanagement.net :: adobe forum volunteer
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