Long term slide/neg digital backup

[rogerd]

I just got a nifty Epson 1650 Photo scanner. One of its features is a slide/negative holder for scanning film. This seems to work quite well - my test scan had sufficient resolution to show the grain in the film, which means that the quality loss shouldn't be too bad.

I'd like to use the scanner to make permanent backups of the film media - scan 'em, and then put the original scans on CDs. Using the automated settings produced a file size (35mm neg) of about 10MB per pic in BMP format (the default). I'm wondering what others would recommend for scanning resolution and file type to get the highest quality image at modest file size. Since this is a permanent record, image quality is the #1 concern, storage requirements are secondary. I'm assuming that CD-ROMs will be with us for a while, but when the next generation of storage devices becomes popular, I'll read in a bunch of CDs and output on the new medium.

If you get digital photos from Kodak film processing, what size files do they give you?

[minnapple]

To determine optimum resolution you must consider the final reproduction size.

For commercial printing you should have a resolution 200-300 pixels per linear inch.
For LaserWriter printing, a resolution of 150 pixels is sufficient.

To print a 5" x 7" at optimum quality, (300dpi) the image should measure 1500pixels x 2100pixels.

[toadhall]

Have a look at Kodak's Photo CD pages to glean archiving tips:
[kodak.com...]

Also do a google search under "digital image archiving methods" (and variations) for what others are doing.

Do you visit Philip Greenspun's photo.net? Lots of information there, primarily film.

[rogerd]

Thanks for the suggestions. One fact I gleaned from Kodak: "the highest resolution level (2048 x 3072 pixels) captures all the image data 35 mm film has to offer..." The standard scanner setting for my new toy captures the picture at about 1500x2400, so there's already some loss there. It's not bad from what I can tell, though - the film grain is quite visible.

How lossy is a high quality JPG file? Going to an 84% JPG knocks the 10 MB down to 350K, more or less. Oddly, it also seems to knock the pixels down to about 1150x1800. I blew up details onscreen, and the JPG seemed to lose a little detail, though the smaller pixel count seemed to be more of a problem than any artifacts of the compression, from what I could tell.

As far as the end use format, I don't know at this point - I'm trying to get the smallest file I can with little or no loss from the original scan at max resolution. This will let me use the image later for whatever is needed.

[minnapple]

The problem with jpg files is that for the most part, they render the image useless for normal print production.

If you view the channels individually you will notice that there are areas that totally wiped out (flattened).

If you try to convert them to tiff/bitmap/psd for printing they become a messy blob.

In short jpg and gif is for video, not for print.
bitmap/tiff/psd can convert down to jpg or gif.

I taught input and output resolution topics in the 80's when scanning/imaging technology was new and expensive.

[rjohara]

(One of the great things about WmW is that just when you're wondering whether or not to ask a question about something, you discover that someone else has just started a thread on the very subject.) :)

I'm graphics challenged, but I decided that this weekend I would bite the bullet and see if I could learn enough to be able to scan some old photographs for archival purposes this coming week.

For the moment I'll just ask one question. Is PNG format suitable to store the master (big) copy of the scanned image? I plan to create smaller copies for the web, but want to be sure I get the big master copy right so I don't have to do the scanning over again. (I can always recreate small versions from it.) I am attracted to PNG particularly because it will store gamma information. I work on a Mac and the GIF/JPG images I make for the web always look dark on Wintel machines; I have saved some test files in PNG format and that solves the gamma problem beautifully.

<added>
And by suitable format, I mean one that could be used for print publication of the image someday if need be, assuming I get the resolution right. PNG is lossless, so should work for this purpose, yes?
</added>

Many thanks to all the graphics experts for their advice.

[mivox]

I'd go with TIFF for quality photo storage. They're huge files, but they're huge for a reason... You're not losing your image data. CD-R media is cheap enough these days, why worry about file size if you're interested in archiving quality material?

Buy a spindle of high quality CD-Rs, archive your images as giganto-TIFF files, and burn all your files onto a new set of CD-Rs every 2-3 years, until a better media format comes along, or DVD burners get cheap.

[rogerd]

Yeah, I was thinking TIF might be the way to go, too, perhaps zipping the files before storing them (although then, in the distant future, one must also have the right unzipping utility in addition to the CD-ROM or DVD-ROM hardware).

What's really needed is a lossless compression format. (ZIP is an example, though it's a general compression technology, not specifically for images.) The files would be bigger than a lossy compression like JPG, but smaller than the initial scan.