Conversion .dng to .jpg

[MARCO35516225uuev]

Hi all, 

when in Photoshop I save a new .dng photo (after editing with Camera Raw 16.1.1) as .jpg the file size drops from 80 MB to 600 KB. What am I doing wrong? Thanks for help. 

[Stephen Marsh · Accepted solution]

JPEG is a lossy compression format. It discards data in order to make the file smaller. At higher quality levels the file is larger than at lower quality levels. This is a feature, not something that you have done wrong, unless you have chosen too low quality.

[MARCO35516225uuev]

Thanks

[D Fosse · Accepted solution]

There's nothing wrong. This is normal.

Jpeg uses very aggressive data compression to reduce file size on disk. That compression is destructive and non-reversible, so the image deteriorates a little bit with each new resave.

The reason jpeg is still used despite this serious drawback, is that it's incredibly effective. It can shrink a file down to 2-5% of native size with little immediate visual degradation. This is why it's so popular for web use.

Uncompressed formats like PSD or TIFF will be bigger than the raw file. That's because one single channel at 14 bit depth is encoded into three channels at 16 bit depth. So that alone will quadruple file size. Jpeg then brings it down to a few percent of that.

Never use jpeg as a working archive format. It's for final delivery, not to be modified again.