Joined: 22 Oct 2004
Location: Oakland, California
Posted: Sun Jun 05, 2005 10:09 am
Each time you modify and re-save a JPEG, there is the possibility of image degradation, even though most times the effect of the compression is not noticable.
However, there is no reason to save any but the final, completely edited version in JPEG. Why throw away data even, if you can't notice it at the time? If you have Photoshop or PS Elements, save your files in native .PSD format -- you'll retain your editable layers, and the .PSD format has its own lossless compression scheme to save space when you close the file.
In my workflow I end up with at least four files:
+ Original capture
+ Edited PSD file
+ Final edited file in TIFF*
+ Final version in JPEG
I do all my editing in PS. When it's done, I save the composite as a TIFF, and it's to this composite which I apply any sharpening or noise-reduction.
I then use the SaveAs command to save this result to JPEG, leaving the TIFF file in its original unsharpened state -- this is so I can go back and repeat these steps later if the JPEG looks cruddy from bad sharpening settings, or if I want to resize the composited image for other purposes.
For stock images or prints I always use the highest possible JPEG quality settings; I only use lower settings if there's a file-size limitation specified (like some for online contests).
*Note: if file storage space IS an issue, TIFF files can be saved using the built-in LZW compression option, which is lossless -- when it is uncompressed all of the data is restored. Also note that if you place an LZW-compressed image into a page-layout program for printing, it will take as long/longer to print as for the original uncompressed image.