Photoshop/Image sizing question
 

I work in the photography biz and know photoshop/printing quality stuff pretty well. This one I don't understand. My wife resized an image in PicMonkey to 1200 x 1200 pixels. It said that the image size was 575k. She emailed it to me and I opened it up in Photoshop, and it gives me a file size of 3.3M. What am I missing here. I'm feeling more stupid than I usually do which I thought was impossible.

Was it saved and sent as a .jpeg file, or something else?

photoshop converted it to a "more information stored" format (psd) for internal use. Probably can't save directly after changes, have to save as psd. You can export it as jpg or whatever you want though.


Totally uncompressed a 1200x1200 pixel image in RGB format (ie, on your screen) would need 4.4mb to display (3 bytes per pixel)

It was saved as a jpg from my wife, and when I drag the attachment off, on to my desktop, it has the jpg extension. So she is sending it as a jpg, and when I drag it off, it's a jpg, not a psd. Is Photoshop still converting it to a "more information stored" jpg? Thanks for your answers and your patience.

Has to be the compression method that was used. I find a lot of mysterious file sizes generated by assorted image handling programs. I don't know PicMonkey, but I'd put it into the 'assorted' classification.

Ok thanks guys. After a couple more tests you guys are right on. It's the compression method, and then when I open it in photoshop it's opening up the full sized image. Thanks.