Image degradation (compression?) in copied threads

[DennisN]

Hi!
I recently noticed that posted images can lose quality when they are copied from a thread to a new thread. It seems they undergo some extra compression, and I don't understand why.

Compare for instance the photos in this PF photo contest thread with the photos in the corresponding vote thread. It is quite visible if you compare the two night sky photos by Marzena.

If it's a bug or feature, I don't know , and I wanted to let you know about it.

 

[Greg Bernhardt]

hmmm I'll have to test. It will be processed again as that is just part of the post action. The compression is lossy so there shouldn't even be extra compression possible and furthermore even reasonably detectable.

 

[Greg Bernhardt]

I see the difference in the twilight gradient. There are bands in the copied version. I don't know a way around this though.

 

[phinds]

I did a check on the image info from each and while some of them are the same in both threads, some are smaller in the voting thread, so some extra compression has happened. In one case the difference was something like 40k down to 15K but most were small amounts lower. Visually I can't tell the difference anyway.

 

[DennisN]

I see the difference in the twilight gradient. There are bands in the copied version. I don't know a way around this though.

No worries . I haven't noticed it before until I looked at my own photo in the PF Night Fever vote thread.