Opening and re-opening files

[Mama Moon]

Someone hinted that opening JPEG's over and over can cause them to lose quality. Is this true, or did they mean if you open, modify, and re-save JPEG's they lose quality? I have a few pics that I thought were fine, but printed out like crap, so I'm wondering if this is what happened to me. Sometimes I will crop them, close them, and the later adjust other things...do I need to start doing this all in 1 shot?

[AirBrontosaurus]

A POTN member did a test about this, and ended up saving a large JPEG 12 times on a low quality setting, and still didn't lose that much detail. Opening and closing a picture a few times won't degrade the image noticeably.

What size was the original picture, and what size did you end up printing it at? If you try to print a small picture too large, it'll look bad no matter what compression you use.

[Mama Moon]

It was a picture that I had cropped down considerably, so maybe I cropped it too small.

[md_129]

Save them as a layered tiff- when you are working on them-when you are finished and ready to send then to the printers ,save the tiff file as a jpeg. :)

[Radtech1]

A POTN member did a test about this, and ended up saving a large JPEG 12 times on a low quality setting, and still didn't lose that much detail.

I did this, HERE (http://www.photography-on-the.net/forum/showthread.php?t=149631) is the thread. Scroll about 2/3 the way down to see my results.

Rad

[CyberPet]

Unless you do serious editing to an image, no you don't lose much quality. Not sure about that test, but if you generally do an edit, save and then reopen he image, do some more edits and save, reopen and so on, it will be some degrading. But depending on the edits there might not be so much new compression to do to the already compressed file.

[SkipD]

I have proven to myself that merely opening, then saving a .JPG, then closing the file, reopening the file and repeating the process 20 times produces noticeable degradation of the image on my computer. Note there was NO editing being done - only the open/save/close cycle. There is a slight difference in the file size count each time as well.

[Strayz]

also, something that a lot of people for get it is a compression format and if you open it with photoshop then save it are you getting the same comresion as if you opened it in internet exsplorer to take a look at it, then save it somewhere else. Not all programs decompress and recompress in the same manor. Isant that when we are saving them in the raw format ? Lossless compresion is all about saving the image for the future.

One example that I think about is what about the server that you save things on, then copy them to a back up drive, replace the server with a new one replacing the images from a back up. You have an image 2 generations old right there. Some of us are replacing computers ever 2-3 years (kinda spooky how fast a image can go bad just by being moved from here to there huh?) Data lost is not going to come back, ever..

So rember YMMV (your milage may vary) and when in doubt just save the Raw or in your fav non compression format.

We are nto paranoid they are out to get all of our images we just dont know it yet.

[gjl711]

...One example that I think about is what about the server that you save things on, then copy them to a back up drive, replace the server with a new one replacing the images from a back up. You have an image 2 generations old right there. Some of us are replacing computers ever 2-3 years (kinda spooky how fast a image can go bad just by being moved from here to there huh?) Data lost is not going to come back, ever..

So rember YMMV (your milage may vary) and when in doubt just save the Raw or in your fav non compression format.

We are nto paranoid they are out to get all of our images we just dont know it yet.
Opening, closing, copying, moving, will do nothing and the data will be identical each time. It is only when you save causing the pic to be re-compressed that there is a chance for error. I read the thread where someone open-saved 20 times and also ran it on my PC. I also did not notice a great difference in the pic either. But when I ran the open - save cycle between three different editing programs or when in photoshop I made a small change, save it, then re-opened and change it back the data loss became much more apparent. Also, you do not loose pixels, the image will have exactly the same number if pixels as it had before. You loose color data