Bruce,
What the program is referring to when it asks you to select a file size is the degree of compression that will be applied to the file before it is saved. Large equals little compression, small is a LOT of compression. In theory, the more compression you apply to a jpg, the more negative artifacts that you'll see in your file when you subsequently view or print it. For example, let's say you have a face in the image. At 100% before saving (and compressing), each pixel in the face has a slightly different tone that appears as a smooth skin gradient. With a LOT of compression, the compression algorithm might take 9 adjacent pixels, average their values and make all of them the same value. ie, you'd get a blotchy-er look. If you aren't seeing any such artifacts when you view at 100% (or print????), then you've probably done no serious harm.
I also imagine that at only 4"x6", the print is too small for you to be able to see such artifacts in the printed version. But I've never tested that hypothesis myself.
Brad
On Nov 20, 2011, at 8:07 AM, Superspike wrote:
> Hopefully someone in the group can clear up some confusion for me.
> I am using CS5 but I think this apples to most versions of PS and PSE.
> I set my image size and resolution and crop, example:
> w-4"
> h-6"
> 300ppi.
> When I save as a JPEG, I an give a dialog box asking to select file size from small to maximum. The example will yield the following results for file size:
> Large - 1.45 MB
> Medium - 157 KB
> Small - 85 KB
> When re-opened in PS, all will still show as having the original settings of 4" x 6" x 300ppi and when zoomed to 100%, seem to have equal detail.
> How can different file sizes contain equal amounts of information?
> What am I missing here?
> Thanks,
> Bruce A.
>
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