JPEGS degrading in quality

[TheNissanMan]

definitely agree!!!

And another thing to consider is that a jpeg image degrades everytime you look at it - so the image you view today might not be as good as the image you look at in one years time (especially if you look at it every day).

Hope that makes sense!

Quoted from another thread but didn't want to take it off topic

I'm confused by this and wanted some clarification, I understood a jpeg file to be a fixed file on a computer as as such unless changes were made to it, it can not change.

If you are viewing a jpg in a viewer which would just be reading a load of 1's and 0's how can it/does it degrade ??

I'm not trying to be difficult but just can't get my head around that comment, any clarification would be greatly appreciated.

Thanks in advance.

 

[awp]

No clarification required really - it's b******s.

If you keep re saving a jpeg as a jpeg then it will degrade.

 

[TheNissanMan]

So only really applicable if your re-opening the jpeg in an editing package not a viewing package?

 

[petersmart]

No digital image degrades just by viewing it - but some viewers - like the Windows Picture and Fax Viewer - are crap for viewing images as they seem to make them a bit unsharp.

Don't know why it should but I always view Jpegs in a browser.

 

[itsdavedotnet]

I've put covers over the top of all the photos and posters on the walls of my house, as they only have a number of views before they start to degrade, it sucks, but I just have to only take the covers off when I have guests around, and ask visitors to only look at them a couple of times so they don't degrade the image too much

jpegs degrade in quality when you save, but other than that, no.

 

[awp]

So only really applicable if your re-opening the jpeg in an editing package not a viewing package?

Nothing to do with opening it - do that as often as you like - BUT if you edit then re-save as a jpeg - over and over then you will eventually notice a difference in quality. JPEG is a compressed format so everytime you save some information is thrown away! Simplification - but you get the idea.

 

[petersmart]

So only really applicable if your re-opening the jpeg in an editing package not a viewing package?

No - it only applies if you then re-save the image as a Jpeg file.

Since Jpeg is a "lossy" medium, every time you edit and re-save you lose some detail.

Do it often enough and the resulting image is noticeably degraded.

If you need to edit a Jpeg it's a good idea to convert it to a Tiff file first then edit it and finally re-convert to a Jpeg when all the editing is finished.

 

[Wigster]

Nope, complete BS.

The "saving jpg multiple times" degradation argument also annoys me as well, yes it it's true some very small amounts of quality is lost; mainly if you're saving in different programs which use different compression methods, but honestly do a test.
Have 2 copies of the same jpeg, one as a "master" then one that you use as your test subject, open it up in as many different programs as you have, then save, do this say 10 times. Then compare/contrast with the "master" the degradation is very tiny, even at 100%.

 

[TheNissanMan]

Learn something everyday, was scratching my head with that one but sort of makes sense