I’ve been experimenting with exports. When I tried exporting to JPG it seemed like all results were slightly smaller in size. I didn’t really want to lose any data so I tried again converting to 16-bit PNG format. I really don’t see how a 2.7MB JPG image can be converted to a 28.2MB PNG image with no increase in resolution. I guess the data is all there but highly compressed in JPG and totally uncompressed in PNG?
Also, oddly enough, all 2+MB JPG’s are producing 28.2MB PNG’s, and 3+MB JPG’s are producing 41.4MB PNG’s. The last several images are 49.5MB. Strange uniformity in size…
JPG compression is designed for photographs. PNG compression is designed for graphics (ie solid colours, smooth gradients etc). So, yes, PNG doesn’t compress photos as well as JPG does.
In addition, JPG is only 8 bits/channel/pixel, and is lossy. PNG is 8 or 16 bits/channel/pixel, and lossless.
PNG is lossless. That makes a great difference to JPG but depends strongly on the quality level and the information in the input image. Increasing from 8 to 16 bit depth multiplies this difference additionally by two.
Choice of output format depends mainly on what you want to do after (displaying, printing , post processing in other SW, archiving…) and should not be based only on size considerations.
With jpg coding you loose a lot of information so only good for display or sent on internet.
Yes. I suggest JPG is never used for anything else. “Lossy” means the compression algorithm changes pixel colours, mangling the pixels. Re-saving the image in another format won’t get the data back.
JP2 is a possible alternative format. It can be 16-bit. It can be lossless, giving files from photos that are smaller than PNG. Or it can be lossy, giving results that are less mangled than those from JPEG for the same size.