Is there a way to have all those 3 things together? Large/high quality/small file size. Because I need to send this file to an office which have rather old computer system (don't ask) to print it. But they all-ways ask me 300dpi document and this time canvas size is really big, but I'm afraid that they will not be able to even open it. So is there a way to get it smallish? Smaller than 3gb (that's what I have now). Thanks. P.S: Photoshop won't even let me save the file in jpg or pdf (I usually use those). Only large formats...
There's no reason why you shouldn't be able to save the image as a JPEG (unless your machine has considerably less grunt than the Atom-based netbook with 2GB RAM I just used to save a Ps document of that size as a JPEG), provided that it's flat, 8-bit and you've selected "Baseline". (Baseline optimized and progressive take more memory to process the compression, and I handily ran out of RAM.) Save off the PSD before flattening and changing bit depth, of course. And if you've had Photoshop up and running for a while, you may need to restart in order to reclaim some RAM.
That should result in a JPEG file that's under 300MB saved with a quality factor of 12. (Two of the images I saved — all random collages of photos I happened to have on my drive — were under 150MB at 12, the others were just over 200MB to about 250MB.) That's still big, of course, but not 3GB big. Still, you'd have to forego the email option and either FTP or stick it in the cloud for download. (And if it's going to canvas, 12 is probably overkill for file size, but it takes less computation to compress than the smaller options. If 10 gives you a memory error, try 11 or 12.)