JPG Image Compression Settings

Mid range compression is the best compromise

I scanned a sample image and saved it as an uncompressed TIF file and at all thirteen levels of jpg compression. Here are the results.

To spot the differences, I suggest you first look at the worst to see where the 'compression artifacts' are most noticeable then track up to where they become no longer noticeable, and then look from the best image and track down to where you can spot the start of quality degradation.

	100 kB TIF (won't display)
	68 kB JPG 12/12 Max quality, least compression
	53 kB 11/12 Nearly as good as 12/12 but 20% smaller.
	42 kB 10/12 Just the slightest hint of loss of detail compared to 12/12, but a massive 33% reduction in size with little loss of quality makes this a good trade-off
	33 kB 9/12 Just starting to see some roughness in the otherwise smooth tonal gradations.
	26 kB 8/12 A bit of roughness and fuzziness now visible, and slight 'halos' around some of the major color changes
	20 kB 7/12 Perfectly good quality for most uses with only the slightest suggestions of quality loss.
	19 kB 6/12 Hard to see any difference between this and 7/12, but slightly better than 5/12.
	17 kB 5/12 Probably acceptable quality for most ordinary 'recognition' purposes
	15 kB 4/12 Fuzzy but the artifacts are no longer quite so apparent
	13 kB 3/12 Poor quality with visible artifacts
	11 kB 2/12 Poor to unacceptable quality
	10 kB 1/12 Definitely unacceptable quality
	9 kB 0/12 Definitely unacceptable quality

What can we conclude from the above study?

First, I think most of us will agree that the smallest file size/highest compression images are of unacceptably poor quality for most purposes.

Second, I think we can probably also agree that for most purposes, 9/12 is acceptably good for high quality as is 12/12, while reducing the file size by more than 50%.

The 'sweet zone' for compression seems to be a setting between 9/12 and 6/12. For 5/12, 4/12 and 3/12, the saving in file size is not worth the tradeoff in quality, and 2/12 and lower are just too bad.

I personally compress thumbnails using a 7/12 setting and full size images at a 9/12 setting. Hopefully the above will help you choose your own preferred settings.