JPG compression opening and loss of info

10 posts / 0 new
Last post
JPG compression opening and loss of info

Was just wondering if any of you know how serious this might be?

It's been several years @ least 3, but I was watching a genealogy show back when we had cable/satellite, and they had an episode on scanned photos and digital cameras.

Their "expert" said that the way JPG's were compressed was EVERY time the file was opened and a new compression was happening every time you were "accessing" the file. And because of multiple compressions, jpg files were not a good way to back-up heritage photos, because they will loose quality after multiple compressions...or that you needed to at least keep a copy that was not opened and closed all the time.

I was wondering if anyone had ever heard this before? I certainly hadn't heard anything like that before~ degrading a jpg. They equated it to making photo copies of photo copies.

Wondering if "windows viewer" or things like Picasa might be enough to instigate a new compression?

I keep backups, but haven't really backed up photo JPG's on disk. I would assume that once burned a jpg on a CD or DVD shouldn't be changing the files, because computers can't be rewriting the information on the disk again.

Thoughts or info?

It's not really true, but parts are...
Here's a link to show you the myths about JPGS. (to be honest, I didn't know either and found this while doing some research on it).

Thanks for sharing the awesome information Jenn!!

Thank you so much Jenn, it was very useful smiley

Thanks for sharing that info smiley

I think it's important to realise that most problems occur with repeated editing and are normally not seen withe the naked eye. If you save your jpegs at the smaller file size, that's where you are likely to see problems. Saving a jpeg at full size, is the best choice if you intend editing and gives you the best chance of enlarging your file without pixelating.

If the only format you can save the pictures in when taking them with your camera it is best to save it at a non compressed state. It does take more file space or results in a larger file. But it is only file spage and SD cards are so cheap today it does not hurt to have a couple of them.

The more you compress the file the smaller the file size, but the quality of the image is not as good. How does jpg compress an image. Think of the sky, it takes up the top of an image. There is texture, but minor. By saving the jpg at a high compression it looks at the sky and reads it as from one point to another point the color is blue. It does not note all of the texture in the sky. It is now flat. The picture will be great for the web, but not for printing.

An uncompressed jpg will show the texture in the sky. If you intend to edit the image in Photoshop, PSP or another quality photo editor save the image in their format. If you intend to share the image save as a jpg at the highest quality. Now you shared a good copy of the image. If you intend to do more edits go back to the software's format and continue to edit. Do not use the jpg, you will find the quality is still not the same, even though it is minor.
I always print from Photoshop also to get a good quality of image.

Remember it is easier to reduce an image than to increase the quality of an image. If you take an image at a low resolution, do not expect the quality to be there if you want to increase the size of the image. So it is better to always take a good quality image even if you intend it to be for the web. Reduce the image, while saving the original.

Note: I am very aware that if one uses Photoshop to increase the size and makes sure that scale, constraints, and resample are checked off - it does take in account the missing pixels and fills them in. It still is not the same as taking an image at a high resolution, quality that contains al of the colors and textures.

I have always taken my photos at the highest resolution the camera offers and when I use a photo I always copy the original and then save it in a file before I ever attempt to edit it in any way.

Her is my question to anyone who might know...recently my sister and I were talking and she was saying that on her Nikon there is the option of taking photos in tiff format? Does the tiff create layers? Or, what is the difference of taking the photo in jpeg or tiff format?

Tiff is considered a lossless compression format. Different from jpg which the compression is call lossy. That some of the original image information is lost and cannot be restored. It may affect the image quality.

If you save a layered image in Photoshop it will ask if you want to save the layers and point out that it can increase the file size. Try it and see how to save as a tiff.

Jpg - you cannot save the layers.

Wow. Lots of good information. Thanks