[csonni]

In my last couple of years of digital photography I have a few curiosities. As of late, I am curious as to why images downloaded (as Preview) are only 160 kbs, and when converted to PS format (same image size with no corrections whatsoever) the size jumps to 580 kbs. Same file but much larger??? What am I gaining by converting them to PS files? I like to keep all my image files in the same type, but if they're going to be so much larger, what's the sense?

 

[ram55]

Preview files are normally jpegs which is a compression file.
When you convert them to psd files it expands the information contained in the image. Jpeg files tend to deteriorate each time they are opened so I save everything in psd format and convert to jpegs when the need arises.

 

[csonni]

Well, I have saved these files as jpeg through Photoshop. So, the file size shouldn't be any bigger, right? Are you also saying that every time I open one of my jpegs it degrades in quality each time? I hope that's not true. All my files will be useless eventually in that case.

 

[ram55]

Images don't lose thier quality when opened and closed only when they are coverted back and forth. Jpeg is a compression file that actually lowers the quality of the image to save space. Go to this site for a full explanation.

http://www.faqs.org/faqs/jpeg-faq/

 

[csonni]

I understand the compression and what not with jpegs, but I would still like to know why a jpeg in Preview is smaller than a jpeg in PS.

 

[ram55]

Preview will display just that a "preview" while photoshop shows all the info contained in the compressed image.