We recently had to wipe our computer's hard drive due to persistent nasty bugs and spyware that our anti-virus couldn't deal with. I had all the digital pics backed up on CDs and have now restored them. My question is this--any pictures I print from now on will be from copies of copies, so to speak. Will there be any data/resolution loss?

quote:

Originally posted by RaroGirl:
My question is this--any pictures I print from now on will be from copies of copies, so to speak. Will there be any data/resolution loss?

Rarogirl,

The short answer is, "NO." That's one of the advantages of "digital," no "generation" loss as we've all seen with analog video "dups." with digital, it's all 1s and 0s-- no in between. Of course, as I'm sure you realize, if you made any improvements since the copies were made, that will be lost. That's no problem; if you were able to do it once, you'll be able to do it again.

Cheers,

Bob

That is good to know, Bob. What prompted the question mainly is that awhile back I opened a photo in Adobe, then clicked on "duplicate image" so I could safely work on a copy. The duplicated image did not look as clear as the original picture and it was fairly apparent. Do you have any ideas as to why the second image wasn't as clear?

quote:

Originally posted by RaroGirl:
That is good to know, Bob. What prompted the question mainly is that awhile back I opened a photo in Adobe, then clicked on "duplicate image" so I could safely work on a copy. The duplicated image did not look as clear as the original picture and it was fairly apparent. Do you have any ideas as to why the second image wasn't as clear?

Rarogirl,

My only guess would be that when you made the copy, Adobe made the copy in a different format and at a lower resolution. That is sometimes helpful if you need to shrink the size of a file, perhaps for e-mail.

I use Corel Photo Paint that will do that if I so desire. It actually lets one set the percentage of compression. As you indicated, if I go too far, the image really suffers. Most software have a "preview" window that lets you see the results, before "saving" the copy. If you want an EXACT copy, use NO further compression.

Good luck,

Bob

Raro,

There are basically two different type of ways in which computers can store pictures - "lossy" and "lossless" compression methods.

Virtually all digital cameras store pictures as JPEG files. JPEG is a "lossy" compression method - it makes the picture smaller by "throwing away" information every time the file is saved, and the result of that is that your picture will get more and more "blurry" the more often you save it as a JPEG.

If you want to edit a JPEG file in a tool like Photoshop or PaintShop Pro, the first thing you should do is re-save it in a "lossless" format such as TIFF. TIFF files do not "throw away" information - they store the picture exactly as it was.

Do all your editing on the TIFF file, and when you've finished, then and only then convert it back to a JPEG, but when you save it, go into the JPEG settings and tell it NOT to compress the file.

If you do this you'll be able to edit your files without losing quality. If you don't, each time you edit your pictures they'll get more and more "blurry".

Thanks a bunch, Chris. Now I understand why the pictures seemed to get worse with each copy. When you save your digitals to a CD or DVD, do you save them in TIFF or JPEG?

quote:

Originally posted by RaroGirl:
Thanks a bunch, Chris. Now I understand why the pictures seemed to get worse with each copy. When you save your digitals to a CD or DVD, do you save them in TIFF or JPEG?

Rarogirl,

I suppose Chris is sleeping right now, so in the meanwhile I'll give you my thoughts about whether backups should be .jpg or .tff.

I've just done a quick test to compare file size of an image (.jpg) as it came out of the camera and compared it to that same image, after converting it to .tff.

The size of the original file was 1.5 mb. The same image, after converting it to .tff, was slightly over 11 mb - almost 10 times as large. Obviously, you would need 10 times as much media to back-up your images. If you needed 1 CD to back up the files as they came out of the camera, you would need 10 CDs to back up those same files if you converted them to .tiff before backing them up. I think you see where I going here. Aside from the media space you would need, keep in mind that you would have to do each image individually (I don't think you can do all your images in 1 shot) and that could be very time consuming.

Remember, there is a difference between "backing up" (copy) your originals and "saving" a file that you have worked on. Your "backup" is IDENTICAL to the original. If you have any doubt about that, compare the file size between the original and the backup: the size will be the same. So, I don't see any advantage to converting your images to .tiff and then backing them up.

As I understand what Chris was saying (and he will speak for himself), "choose an image that you intend to work on, convert it to .tiff, do whatever editing it needs, and then go back to .jpg." My point is: the conversion FROM .jpg TO .tiff from the original file or the backed up file is the same -no loss. Remember, I'm addressing your question regarding backups, not whether you should go the ".jpg to .tiff to .jpg route. "

Personally, I don't deal with .tiff files, (probably because I'm too lazy) but I understand Chris's point. I handle it differently.

Bob

quote:

As I understand what Chris was saying (and he will speak for himself), "choose an image that you intend to work on, convert it to .tiff, do whatever editing it needs, and then go back to .jpg." My point is: the conversion FROM .jpg TO .tiff from the original file or the backed up file is the same -no loss. Remember, I'm addressing your question regarding backups, not whether you should go the ".jpg to .tiff to .jpg route. "

Yes, exactly - sorry if I wasn't clear on that point.

The original JPEG format is fine for storing backups of files - digital copies are "exact", no matter how many times you copy them. What I was saying is that if you're "editing" a picture in a program such as Photoshop or PaintShop Pro, then don't repeatedly save it as a JPEG or else each "generation" of the file will lose more and more quality.

Ok, thanks you guys. I think I understand the concept now. Anyway, I am glad I asked the question before doing any more work on photos.

Rarogirl:

You can work on your original all you want no matter what the file type. Your original will not be changed until you save the copy you have worked on. If you are not sure of your changes, save it under a slightly different name: xxx becomes xxxa. Once you are happy with your changes, save it over the original with the original name. Sometimes you will like both versions and keep them both.

Glenn

Good tips, Glenn. I have just always heard you should work on a copy, but you are certainly right that until I save the changes it will still be the original picture. I will try your idea of saving the file with a slightly different name.

Raro,

Just in case this isn't clear yet, the problem occurs when you open a JPEG file, edit it, and then re-save it as a JPEG.

Each time you save a JPEG file then, by default, information is "thrown away" to make the file smaller. Eg if the application is set up to throw away half the information then the first time you save it you have half the original information; if you resave it you end up with a quarter of the original information; if you save it a third time you only have 1/8th the original information, and so on. You very quickly end up with a blurry mess.

If you do want to edit a JPEG and re-save it, it's vitally important that you tell the editing program NOT to throw away any information when it re-saves the file. The way you do this varies with the program. In PaintShop Pro (the editing program I use), for example, you select "Save As", then click the "Options" button to display the JPEG options selection, and drag the "Compression Factor" slider down to zero.

Just to confuse the issue, some programmes have a quality setting, in which you need to drag the control to 100. (100% quality = zero compression)

I have a couple of different programs I use so I will have to check them out to see what my options are when I save. I think I understand the basic concept now. Fortunately, I have always done all my work on copies while keeping the orginals, so at least they are still intact with no data loss.