sequential loss in jpeg

EM
Posted By
Eric Matthes
Aug 24, 2003
Views
151
Replies
5
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Closed
I understand that every time you open a jpg file in photoshop and resave it as a jpg, you lose more and more data. But what about copying files? When I open a desktop folder and copy the jpegs from the folder to a CD, is there any loss of data? Or are the copied files identical to the originals?
Along the same lines, my current saving routine is:
* Upload images from card reader to a folder on the hard drive(images were taken as fine jpgs) * Save images to CD-R
* On working with an image, save as PSD or TIFF
Am I losing any data in this process, aside from the choice to use jpg over TIFF in the camera? Would I be saving any quality by immediately batch processing the images to TIFF format before saving to a CD?
Thanks.
Eric
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JD
Juergen D
Aug 24, 2003
Eric,

No, you are not losing any data in your procedure as long as you are not using any photo software to accomplish this. All you are doing is copying a file twice. There is no change to it in the 2 steps you are taking. If your original image off the card is in Jpeg, there is no reason to change it to TIFF before saving. To the contrary, you may have a data loss in that step, since you have to open and resave with Elements (I’m not sure about this.)

Juergen
JG
Julio Guerra
Aug 25, 2003
As I understand it the data loss comes from SAVING a file using the Jpeg routines. Opening and then saving the file to TIFF does not lose anymore data.

The Jpeg save compresses the file each time it is saved. Saving and resaving a file causes the routine to compress a compressed file.

Saving in TIFF does not. Correct?
Julio
RC
Richard Coencas
Aug 25, 2003
Correct
RG
roland green
Aug 30, 2003
I am fairly new to all the formats and I would appreciate it if someone could Help me. I am a teacher working on our yearbook and we are using sony digital cameras and photoshop 7.0 for editing.
Question: Should I work in JPEG format?
I am not sure what is the best format to use for we will open the files to view and possibly to do more editing.
Appreciate Your Help!
Roland Green
EM
Eric Matthes
Aug 30, 2003
Roland,
When you first open an image in jpeg, save it in psd or tiff format. These formats save all the information in the file. When you open a file you have previously saved as a psd or tiff, you are opening the exact same file you last worked with. When you save an image as a jpeg, it throws out any information it considers "extra".
Jpeg is really for use when file size is an issue: for web images and emailing. If you are printing, you probably want to do all your editing work on files in psd format, and then save the final edited image as a tiff with no layers. (If you are using layers.)
Perhaps the most important advice, is to save your original unedited images on a CD before doing anything else to them. This way, no matter what mistakes you make (or students make! – I’m a teacher too), you can always go back and start over with the original file. This is particularly important if students will be working on the images. They are notorious for saving a tiny thumbnail image over the original image file.
Eric

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