I am scanning 35mm color slides, some 50 years old, with a Nikon scanner. Should I save the scanned image in jpeg or tiff format for saving on archival CDs?
JPEG is lossy, so the image loses some detail, but the file size may be smaller and compression and extraction can be faster. Wikipedia states, "[It] somewhat reduces the image fidelity... JPEG is also not well suited to files that will undergo multiple edits, as some image quality will usually be lost each time the image is decompressed and recompressed."
TIFF images are larger, but do support lossless ZIP and LZH compression.
If you use or ever plan to use high-end image editing tools (e.g. Adobe Photoshop), TIFF would be preferable. If you're concerned about disk space, JPEG might offer an advantage, though at the expense of image accuracy. JPEG's are also the most convenient form for using on a website or for sharing with friends.
One other option: have the photos scans saved in both formats, or at least in TIFF, and then use any of a number of free (e.g. IrfanView) or commercial utilities to convert to JPEG as you want to share them. It is easy to convert a batch of them. That way you'll always have the maximum-fidelity TIFF to fall back upon.
Thanks. With re to your comment about multiple edits and losing quality, do multiple viewings of photos on a CD meet your definition of multiple editing? Once I complete the editing at time of scanning/saving, I don't plan on further editing. Jun 28, 2015 at 11:33
For archival purposes it makes sense to scan in a lossless format. Depending on what software you are using, you can save NEFs from Nikon Scan, or RAW from VueScan. I prefer that latter, because it saves the actual data coming from the sensor, thus allowing for lossless editing in the future.
Thanks for your response. I'm using a Nikon Coolscan VED scanner and the editing software that came with the scanner. I am scanning 35 mm slides, mostly Kodachrome, some Ektachrome. Some slides are 50 yr old. Once saved after scanning/editing onto CD's, I don't plan to edit further, but do plan to view them multiple times. Does that make a difference re what format to save them in? Jun 28, 2015 at 11:51
@Bill : I would be saving NEFs for archival purposes, and JPEGs for viewing. Jun 28, 2015 at 14:54
JPG: 8 bits per color channel, the data compression dismisses small details in the information provided by the scanner; i.e. the compression is "lossy".
TIF: Possibly 8 but also allows 16 bits per channel - Packbits, ZIP and LZH compressions are lossless.
For archival purposes I'd use TIF 16-bit.
The files may though become huge, especially in comparison to JPGs.
Depending on actual model - a dedicated film-scanner of makes Nikon, Minolta, Plustek, Reflecta / Pacific Imaging come in somewhere in the range 3000 to 5000 dpi.
Note the difference between the SETTING in the software and the ACTUAL result - the latter is the important and what I refer to above.
Even if you scan at a setting of 6400, 7200 or 10000 dpi (which some of the scanners allow) you won't get actual data above 5000 dpi, but rather a notch or two below.
From this follows that pulling up the scan dpi above a certain point (scanner dependent) is just a waste of time and harddisk space.
Thanks. I'm using a Nikon Coolscan VED scanner. It allows the choice of file size (MBytes) and Resolution (pixels per inch). What settings would you recommend in response to your comment? I am using the Nikon software that came with the scanner and don't plan to edit further after saving. Does multiple viewing of the saved photos on a CD constitute further editing? Jun 28, 2015 at 11:46
filmscanner.info/en/NikonCoolscan5ED.html <- assuming that is the scanner you're using. If there is a "PPI" setting just higher than 4000 then use that for the highest achievable results. NOTE: This is a theoretical number, the actual result will depend on camera focus, and how well the scanner succeeds with focusing on the negative and other intermediate factors. 4000 dpi/ppi creates output in the vicinity of 22 megapixels under PERFECT conditions. Use any lower setting for less bulky files. Even 6MP is enough for A4 size prints (~12x8") at good quality - assuming "perfect" images.– HannuJun 28, 2015 at 17:29
Does multiple viewing of the saved photos on a CD constitute further editing?Ehh... no. You cannot normally change what has been written to a CD. Viewing an image is equal to reading it up into computer memory for display. The CD plastic ages, that is the only factor that might degrade or eventually destroy it apart from physically damaging the disk.– HannuJun 28, 2015 at 17:35
Thanks for your feedback. I plan to save the most valuable family photos on archival CD's. The others, I will periodically resave recognizing that CD's have limited life. My 35mm slides cover a period of about 50 yrs and the older ones, like me, have suffered some degradation. Jun 29, 2015 at 17:15