Question about JPG and PNG images

[mresc]

Hello, I had a question regarding preserving the quality of images. I recently found out that JPG images "lose quality" every time they are saved or even opened, and this was depressing to hear as nearly all the images on my computer (which is practically a database of images) are JPG's. >:[

I know I will want to back these images up multiple times and carry them over to other computers years from now (without losing quality), so my question is that if I convert them all to PNG format, how big will the initial loss of quality be, if at all? I know that converting to PNG wont make the images "better", but will doing so prevent loss of quality from their current state in the future? (or is there another format instead that I should be looking to convert to?)

Thanks

Additional info:

- Most of these images were saved from the internet, many being JPG's to begin with.
- Their sizes vary, but most are larger, wallpaper sized pictures (1280x800, 1920x1080, etc)
- The images are mostly for reference, but I will probably end up copying + editing some of them in some way

 

[SCraig]

JPEG files do NOT lose any quality when they are opened, however they can lose significant quality when they are saved. It all depends on how they are saved, specifically the amount of compression. Opening them has NO affect unless they are subsequently saved again after opening.

 

[The_Traveler]

no,no,no

major misunderstanding

if you open a jpeg to look at it/ copy it or anything and then close it, no problem, no changes, it will stay OK forever
if you open JPEG, THEN EDIT IT AND RESAVE many times that's when you are introducing deterioration but even then it takes a while for that deterioration to show.

 

[mattyclown]

JPEG files do NOT lose any quality when they are opened, however they can lose significant quality when they are saved. It all depends on how they are saved, specifically the amount of compression. Opening them has NO affect unless the images are subsequently saved again after opening.

Does that mean when I open a jpeg file with an image viewer, display it without editing it and then click the save button and close it, the jpeg image file will lose quality? This sounds a little unreasonable.

 

[The_Traveler]

no,no,no

major misunderstanding

if you open a jpeg to look at it/ copy it or anything and then close it, no problem, no changes, it will stay OK forever
if you open JPEG, THEN EDIT IT AND RESAVE many times that's when you are introducing deterioration but even then it takes a while for that deterioration to show.

^this

 

[KmH]

JPEG files do NOT lose any quality when they are opened, however they can lose significant quality when they are saved. It all depends on how they are saved, specifically the amount of compression. Opening them has NO affect unless the images are subsequently saved again after opening.

Does that mean when I open a jpeg file with an image viewer, display it without editing it and then click the save button and close it, the jpeg image file will lose quality? This sounds a little unreasonable.

Which image viewer?
If you can, just click on the Close icon rather than clicking on Save.

JPEG is a lossy, compressed image type. JPEG - Wikipedia, the free encyclopedia
JPEG was designed to be a final, ready to print image file format. JPEG - Joint Photographic Experts Group - Wikipedia, the free encyclopedia
PNG is Lossless - Portable Network Graphics - Wikipedia, the free encyclopedia

 

[Light Guru]

In addition to all that has been said about jpeg files, you should also know that there are better formats for preserving quality then PNG. I would go with the TIFF format any day over PNG for preserving image quality.

 

[SCraig]

Does that mean when I open a jpeg file with an image viewer, display it without editing it and then click the save button and close it, the jpeg image file will lose quality? This sounds a little unreasonable.

Yes, it does. Any time you re-save a JPEG file the software goes through the compression algorithms and it will lose slightly more quality. How much depends on the software (some have adjustable levels of compression, others don't). As KmH stated, as long as you just close the file without saving it then it will not change.