Sample Images with Loss of Quality 1: Color Shift

Slight color shifts are part of the JPG algorithm and occur even in best JPG quality – but do not matter for the perceived image quality.

On the right you see the same image as before, uncompressed, without any loss of quality. When you move the mouse pointer over it you will now see a JPG image of good quality, now compressed more to less than one tenth of the uncompressed file size.
If you look really close there are slight color shifts (e.g. around the dark spot in the red blossom) – but if you see only one of the images it is impossible to say which pixels have a „wrong“ color.

And again: The differences are really tiny. When printing the full image as a poster about 40 cm or 16“ wide the snippet would be 2.5 cm wide and you would need magnifying glasses to recognize the differences.

That is the reason for the success of the JPG format: High compression without visible loss of quality.

Additionally you see an artificial image on the right to visualize the effect of color shifts better. Again you see an uncompressed image of „perfect“ quality and the same JPG compression as before when you move the mouse pointer over it. Watch how the blue changes slightly.
And very, very faintly you can recognize how the yellow background around the circle changes. This is the next type of quality loss that gets more visible with higher compression, see the next section.