My client wants a high res file 1 MB or higher. My Photoshop file (CS4) is 5 MB when I open it in Photoshop (4.5 inches square and 300 dpi)- when I look under Image size. But when I close file it says "875 KB" in my hard drive folder. What am I doing wrong? Client won't accept file until it reads as 1 MB when I email to her as an attachment.
You must have done more then close it. You must have saved over the 5MB file using a lower quality setting so the encoded jpeg image was compress more and you lost some image quality.
Also 4.5x4.5 @ 300 DPI is 1350px by 1350 Px. I just create two jpeg file for two document that size saving at quality 10. One image was a blank white background it save size was 65KB the other document was a spectrum gradient with a lot of noise added its save size was 3.5MB. Image content is also very important. Little detail little file size great detail larger file size.
You're comparing apples and oranges.
"File Size" in photographer speak is a measure of horizontal pixels x vertical pixels x 3. It's shorthand developed in the days of making 8 bit RGB tiff files from scans.
Your image is 1350 pixels square. Photoshop accurately gauges that, in photographer speak, as 5 MB in the Image Size dialog. You're actually well over the requirement of your client from the sound of things.
Ignore the file size on disk. That's compressed data and isn't related to what your client has requested.
But if there's any question, let your client know the pixel count and confirm that it's within their requirements.