Before the rush

Before the rush
by evan-pak

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This question already has an answer here:

In Photoshop, while saving an image as JPEG, there is an Image Option called Quality.

Increasing or decreasing the value, only increases or reduces the size of the JPEG file.

If we try to zoom in the images saved in different quality values, there is no difference.

Then why there is Quality option? What is the real use and need of this option?

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marked as duplicate by mattdm, Michael Clark, Paul Cezanne, AJ Henderson, inkista Aug 4 '14 at 18:30

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Take two qualities as different layers, chose difference, then adjust contrast and have a look – PlasmaHH Aug 3 '14 at 20:05
Make sure you are looking at the saved images after you close your original image. You'll see the difference, then. – B Shaw Aug 3 '14 at 21:26
up vote 4 down vote accepted

You say "if we try to zoom in the images saved in different quality values, there is no difference", but, actually, that's just because you're not looking closely enough, or don't know what to look for. If you choose an extreme value (very low) the difference should be obvious. At higher settings, it's more tricky, but usually there's a difference there too even if it's harder to detect by eye.

Take a look at What are jpeg artifacts and what can be done about them? for the result of JPEG compression, which will be more apparent at lower quality levels, and Pentax K-5: Is it worth using the Premium JPEG quality setting? for some additional examples.

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