I have just finished retouching a session and saved the images as JPEG the same way I have done for every other session. Now as I go back to look at these images before uploading them, the file size has been greatly reduced. The original is 2 or 3 MB and the saved retouched image is 800 kB. I haven’t changed anything in my settings (that I know of) but just wondering how I can prevent this from happening on my subsequent sessions and is there a way to get these saved edited images back to full size? I am do not have the option to change the quality from 7.
This is what jpeg compression does.
The jpeg algorithm uses very aggressive data compression to reduce file size on disk, so that the file footprint is reduced to maybe 2-10% of original size. This is data packaging, it has nothing to do with resolution, which stays the same.
Jpeg compression is destructive, non-reversible and cumulative. A jpeg cannot be fully restored to its original state. For that reason jpeg should be considered a final delivery format, never a working/archival format.
Unless you know why you'd need a JPEG, you probably don't want one, you're introducing data loss that can't be undone!
I have to deliver the images to my client as JPEG's. What is the best way to do that?
As for why you perceive this as a sudden change: previously you may have worked with jpegs that were already compressed. Then you will only see a small change in file size.
When you open a jpeg, it is decompressed back to its former full size. So that becomes the new starting point if you resave to jpeg, and it will end somewhere in the vicinity of the original file.
But once again, it needs to be stressed, resaving a jpeg is something you shouldn't do if it can at all be avoided. Keep master files as PSD or TIFF.
I have to deliver only jpeg to my clients. What is the best way to do that
Save a Copy as JPEG, and keep the original (TIFF or if you must, PSD). That way you've always got the high quality image data.
You can use a number of methods to save off this JPEG, again, Save As.... (JPEG), Save for Web (Legacy is my preference), etc.