Compression ratios and image quality

This page demonstrates with side-by-side photos how various compression ratios affect image quality. All of the manipulations were done before I owned photoshop. They were done using some of the free software I reccomend in the article.

For this example I started with an original JPG image, DCP_0564, which was 2160x1440 pixels and was 811KB in size. That image was cropped to eliminate the unwanted portion and saved as an uncompressed JPG file. The new file, shown below in the top left position was 415x275 pixels and 92KB in size.

I than shrank this file by 25% and again I saved it with no compression. I named this new file 0564_crop(311x206).jpg. The new file size is only 56KB and is shown in the top right position. The new file is only 25% smaller in viewing size but it is 39% smaller in file size.

If you did not open this window from the article mentioned above and you would like to read the article. Click on the Web Quality Photos File size and Compression link below.


More Articles in this Section

●Image Resizing and Compression Programs
●Web Quality Photos File size and Compression
●error_log


0564_crop.jpg    uncompressed image 415x275  92KB 0564_crop(311x206).jpg uncompressed file 56KB


For the compression testing I started with the 0564_crop(311x206) pictured above on the right. That uncompressed image is repeated in the left column all the way down this page so that you may make a side-by-side comparison between the original and the compressed images. I used the original uncompressed image each and every time. That is very important since each time you compress an image some small loss of quality occurs. Repeated compressions magnify the problem. I tested the two programs reviewed above in 10% increments of compression. It is important to note here that the files are named for the amount of compression that took place during the save. Compression factors are not necessarily uniform between different programs.



0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_90.jpg   20KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_80.jpg   13KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_70.jpg  11KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_60.jpg  9KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_50.jpg  8KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_40.jpg  7KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_30.jpg  6KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_20.jpg  5KB
0564_crop(311x206).jpg uncompressed file 56KB 0564_crop(311x206)_10.jpg  3KB