[911pcars]

Try shooting at different camera resolutions.

I've found a 400-600K file size to be fine for 4x6s. For example:

In Photoshop, a 72 dpi image with the following dimensions:
Pixel width = 2288
Pixel height = 1712
Document w = 31.7 in.
Document h = 23.7 in.
File size - 356K

..... is equivalent to a 300 dpi image with:
Pixel width = 2280
Pixel height = 1712
Document w = 7.6 in.
Document h = 5.6 in.
File size - 356K

Same number of pixels; however, one file has them spread over a 31x23 in. document dimension, the other over a 7.6 x 5.6 in. dimension, but they're equivalent.

As a test, give your photo processor an image shot with different camera settings (use a cue card so you can ID them), make a 4x6 in. print of each, then see if you can find any quality differences between them. You might find very subtle differences, if any.

However, you don't want to shoot that once in a lifetime image at the lowest 4x6 resolution. It won't look as nice at larger sizes, and while there are software programs to replace missing pixels, you usually don't want to go this route. Shoot as high as you can, then use a photo program to reduce the resolution specs (above). Archive the original, dump the rejects, and print the reduced size version.

Hope this helps,
Sherwood

Edited: corrected some numbers in the text to match