Dramatic loss of quality when saving to jpg

[victoria34067134d4xp]

I've just opened some images which I last worked on 3 months ago and see a dramatic loss of quality ie noise and speckling and distortion of pixels giving a water mark effect on my photograph.  This was not on the original photograph - I always save to jpg at the max quality and I am at a loss as to why and how this happened and what can I do to fix this. I post 2 images one from the original and one that is after editing where you can see the dramtic difference in quality. 

Anyone any ideas what to do about this as I don't want this happening again.  This is not happening all the time but seems to be randomly happening, I have used photoshop for years and never experienced this before.

Using mac sonoma 14.4.1 and latest version of photoshop

[Kevin Stohlmeyer · Accepted solution]

@victoria34067134d4xp jpg in general is considered a "lossy" format even at max settings. Save your working images as native PSD.

https://www.adobe.com/uk/creativecloud/photography/discover/lossy-compression.html

[victoria34067134d4xp]

Thank you so much for your reply I will certainly be changing the way I save my files in future!

[D Fosse]

There is no such thing as maximum quality with jpeg. The jpeg compression algorithm is always at work, and it is always destructive, non-reversible and cumulative - even at the maximum setting.

Every time you resave a jpeg, it is degraded further. This degradation is permanent.

The only reason jpeg is still used, is that the size reduction is amazingly effective. It can shrink a file down to 2-5% of the native size, with little immediately visible quality loss, at least for the first generation. Do it again, and it will become more and more obvious.

[victoria34067134d4xp]

Thank you so much for your reply