Examples of JPEG Compression

I took this photograph with an Olympus Camedia 1400. This camera was, in 1999 one of the best digital cameras available. It had three resolution settings. This picture were taken on the highest quality setting. The image was then viewed and manipulated with PaintShop Pro 5.0 and saved as a jpeg image using various levels of compression. The percentage file sizes shown are relative to the original ‘.jpg’ file downloaded from the camera. The thumbnail pictures below, show the area most affected in visual quality by the compression for each setting. These link to the full images if you want to do a detailed comparison. From these images you can see that there is very little difference in the image quality with quite high levels of compression. In my opinion a setting of 20, which reduces the image size by 2/3 has almost no discernable effect on the quality of the image. Whilst a setting of 90 is stll a fairly good representation of the original.
I have also included the size of the image when saved as ‘.gif’ as this is very popular on web sites and as ‘.bmp’ which is, at least in theory, a lossless format. Disk space and time discourage me from uploading a full size bmp file.

PSP5.0 Setting File Size relative to best quality jpg Image
bmp 3.8M 409% Download cropped bmp
gif 1016K 108% Compressed Flower
1 938K 100% Compressed Flower
10 419K 45% Compressed Flower
20 292K 31% Compressed Flower
30 230K 24% Compressed Flower
50 168K 18% Compressed Flower
70 120K 13% Compressed Flower
90 52K 6% Compressed Flower
99 16K 2% Compressed Flower
This graph shows the relationship of file size with setting for PSP5.0 accross the full range of settings. Graph of filesize