More on photoshop file sizes

[DanK]

Well, I should have known, but in case anyone else also missed this: Photoshop asks about compression twice when saving.

In an earlier post, I showed that in the case of some test images, LZW compression isn't very useful with TIFFs and can even increase file size. I didn't find much advantage from ZIP compression either. However, that was because I wasn't paying attention.

The compression choices at the top left of the save as dialog apply to the composite. This isn't noted in the dialog. To apply zip compression to individual pixel layers, you have to check that option at the bottom right. In years of using Photoshop, I never noticed that. it made a very big difference in the two images I have tried so far.

[proseak]

In my experience, LZW compression is useless for 16-bit Tiffs, making the file size bigger than uncompressed files.