file size / cropping

[echoyjeff222]

just wanted to make sure I didn't majorly screw something up. I cropped 6x8 and 300 resolution for printing, and the file size dropped from 8 mb to 2 mb. Is this normal?

 

[480sparky38 37]

What level of compression did you save it at (i.e., 75% 90%? 100%).

 

[TCampbell]

With no compression at all a 6x8 at 300dpi works out to 4.32 megapixels. In an 8-bit color depth image (times 3 channels) that gives you an uncompressed file size of just under 13 MB. But JPEG compression is VERY efficient! JPEGs are usually dramatically smaller.

 

[Ysarex84 78]

Yep, that's normal but you may not want to save that change as an overwrite of your original file.

When you say you cropped do you mean you cut away data from the edges of the photo so the result was 6x8 or do you me you re-sized the photo down to 6x8. Was the photo already 300 ppi before you cropped it?

The change in file size means you're losing data. If you're losing data because you discarded parts of the photo and it was already 300 ppi then you're fine as long as you're sure you don't want that cut away data back.

If on the other hand you re-sized the photo down to 6x8 from a larger size then that loss of file size means you're discarding resolution and that would be very bad if you ever want to make a print larger than 6x8 in the future. In that case you want to re-size the photo without holding the ppi to a constant value -- it'll go up.

Joe

 

[echoyjeff222]

I simply used the 8x10 crop function in PS ... I think that's okay, right?

Interesting. So I didn't put anything in the resolution tab, and now it's back up to 6 mb. When I put 300 ppi in the tab, it goes down to 2 mb!

 

[Ysarex84 78]

I simply used the 8x10 crop function in PS ... I think that's okay, right?

Interesting. So I didn't put anything in the resolution tab, and now it's back up to 6 mb. When I put 300 ppi in the tab, it goes down to 2 mb!

Sounds like when you put 300 ppi in the res box you're sampling down -- don't do that. There's a check box for Resample; make sure it's checked OFF.

Joe