Compressed PSD files in CS3?

[CatCynic]

I do not know if this is new or not, but I just noticed that CS3 appears to be creating compressed PSD files.

I use a Canon 5D, shoot RAW and convert using Adobe Camera Raw. Using PhotoShop CS2, my full-size first-cut PSD files were 72Mb (12Mpixel x 3 channels x 16 bits, so that makes sense) - uncompressed and taking up heaps of disk space.

Using CS3 they are MUCH smaller (20 to 40Mb), and vary in size a lot. I'm guessing that CS3 uses a loss-less compression on the PSD files.

Is this a new feature of CS3? Or was it available in CS2, too? Either way, I really like it, because it is saving me a lot of disk space, and makes my backups smaller.

[R_Fredrick_Smith]

I tried an experiment to see what would happen. Here is a screen shot of the folder where I stored the test photos



The photo was taken with the Canon 20D in RAW. I Saved it out of the RAW converter from CS3 as a tif file. The image has the name img_5421.tif. I then loaded it into CS3 and saved it out as a PSD file. I then loaded it into CS2 and saved it out as a PSD file. The image was in 16bits. You'll notice that the CS2 file came out a lot smaller than the CS3 file??? Also note the ones marked test5421 were the same test, but with a 8 bit file.

I don't feel like Adobe would have added a undisclosed compression to the PSD file format in CS3. If they did, then those files would not be backward compatible and that would cause a major snafu in the industry (if it was undisclosed). But then how does one account for the file differences I see in my test???

Could the RAW converter be the difference, I wonder?

Cheers,
rfs