Tom Williams wrote:
A friend of mine took a bunch of photos using her Vivitar 3.2MP digital camera with the camera set at 640x480 resolution. She wanted 4x6 prints of those and printed a bunch that came out looking all pixelated and basically like crap. Since then, we've set her camera back to the max resolution since previous photos taken at this resolution printed fine as prints.


My question: is there anyway to use Gimp to scale the 640x480 images so they look as best as possible (no pixelation if possible) as 4x6 prints? I've scaled the images to 4"x6" and have increased pixels per inch and have run many filters with no real success. Or is my friend basically stuck with what she has?

You can resize the image up in "steps" to smooth out the pixelization and rough edges as you resize it, but you will never regain the missing detail that was not recorded when the photo was taken at such a low resolution so the resulting image will be soft. (Sharpening will help some, but not a lot.)

To upsize in steps, increase the image size by no more than 10% (some say no more than 5%) at a time until it is at the desired size. For minimum quality 4x6 print you want 150 dpi which means you need 600x900 pixels (her 480x640 will need to be cropped as it is the wrong proportion for a 4x6, which means you need to resize it larger, then crop), for better quality you want 300 dpi which means 1200x1800 pixels. Upsizing in 5% increments takes 22 steps to get to ~1200x1800:

        480     640
1       504     672
2       529     706
3       556     741
4       583     778
5       613     817
6       643     858
7       675     901
8       709     946
9       745     993
10      782     1042
11      821     1095
12      862     1149
13      905     1207
14      950     1267
15      998     1331
16      1048    1397
17      1100    1467
18      1155    1540
19      1213    1617
20      1274    1698
21      1337    1783
22      1404    1872


Upsizing in 10% increments takes 11 steps:

        480     640
1       528     704
2       581     774
3       639     852
4       703     937
5       773     1031
6       850     1134
7       935     1247
8       1029    1372
9       1132    1509
10      1245    1660
11      1369    1826

10% goes faster, but only you can tell if the slower method will produce an improved result on this particular image.

I'm not presently using gimp (I gave up and returned to photoshop and am mostly lurking to see if using gimp is something I should try again in the future), so I can't tell you the exact method for resizing but I hope that this is something you already know how to do.

jc

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