I have just purchased a Film/Slide scanner (CoolScan III) to archive the family photos and slides for future generations Im planning on putting the scans on to CD for distribution and backup. My question (The Eternal Question) is at what resolution should I scan them.? My initial thought was to get as much information as possible about each slide so that If technologies for displaying and printing digital images changed the scans would be as good as possible. Assuming that the originals were lost or had degraded this would be all that was left of the original. However at 3856 X 2573 X 16M JPEG thats 11.4 Meg per Slide. Am I really preserving that much more useful information by scanning at this resolution or am I just wasting space? Any thoughts would be much appreciated.

-- Reno Giovannetti (renog@pacbell.net), May 20, 2000

Answers

You may get a smaller jpeg file than 11 megs from a full resolution scan depending on the detail in the slide. The more detail the larger the image file. The next resolution down for your scan is to go to about 1350 dpi and at that resolution you will lose 3 times the information. File size will be 1/4 that of the scan you can actually make. It just means that you need to make more cd's and at 1.50 per that is cheap compared to the problems later on.

-- Jonathan Ratzlaff (jonathanr@clrtech.bc.ca), May 20, 2000.

Reno, It depends on the future intent for these scans. If you want to archive them to CD for future printing, then the JPEG file format is not for you. Use the TIFF format.....this format is lossless and allows you to use the LZW compression algorithm. JPEG is really intended for web graphics because of the extreme compression ratios (like 10:1 in some cases).

As for scanning at full resolution, it has its ups and downs. If you have a full res scan and want to output it to a 300dpi printer @ 8X10, you have no problems. But if you want to e-mail a photo to a friend and need a 640X480 pixel JPEG, then you can lose quite a bit of detail in the resampling. Depending of course on what interpolation method you are using. In any case there are proven techniques that work, so scanning at max resolution does not hurt.

If you have the time, I would suggest scanning one image at a low res and one at the highest. If you do not have time for this, however, then the largest file wins the race, with the best overall flexiblity.

-- Jason M. Kirk (jasonkirkphoto@hotmail.com), May 22, 2000.

Hi Reno:

Along another vein...I too am interested in putting all my old slides on CD's for our children. But how does anyone show them, except through a computer. Does anyone know of a "projector" that would emulate the old Carousel, but use a CD as the source instead of the Carousel Tray.

-- J. A. Rovane (agrovane@interl.net), May 22, 2000.

I'd have to go with the "bigger is better" crowd on this one, with the one caveat being that future use is really the best determining factor. By that, I mean that 8x10's are a good possibility, but I wonder why future generations would be compelled to print 8x10's from images you may not feel are truly that significant?(since you wonder if the hi res scans are worth it?) Granted no one has a crystal ball, but it seems to me that an 8x10 at 300 PPI will probably be sufficient for nearly any use, except for large blow-ups for party favors, special photos, or something similar -and probably good enough for them if you use a fractal encoder.

On the other hand, I'd advise you that you might want to consider a method of compression. An image compressed to 1/4 it's size with jpeg compression is usually a very good representation of the original file due to the fact that most images have fairly large areas of similar or identical color unless they are very high contrast and very highly detailed, indeed. An even better method might be to use Genuine Fractals to convert the images to a fractal storage method and save the resulting smaller, but highly scalable files on the CD-Rom disc. Frankly, one format has just as good a chance at long term use as another, and so far fractal compression seems to offer the most flexibility in terms of scaling images up or down without loosing significant detail.

Perhaps you'd consider that an evening spent selecting a cross section of images, maybe 5 or 10, representing different types of scenes, and then saving them in various formats and files sizes and printing them to see what you feel is acceptable in terms of file size/print size tradeoffs is worthwhile? That way you could maximize your storage while still being comfortable with the output quality. It's likely there will be improvements in output quality, but I doubt they'll ever increase output quality beyond the level where a 4:1 jpeg compression will be radically inferior to a full size Tiff of the same image and I'll lay long odds that a fractally compressed image will fare even better!

Good Luck.

-- Gerald M. Payne (gmp@francomm.com), May 22, 2000.

Responding to the question about a CD-Rom projector, I doubt one exists yet. About the closest you'd get currently would be an LCD projector or panel(with an overhead projector) hooked to a PC or laptop unless someone has gone and combined the two? With current projectors, I doubt even the most expensive would project images at higher than 1280x1024 resolution, if that. As I recall, most are rated at 800x600 or 1024x768.

For now, perhaps the simplest, but lower quality method is to dump the images to video tape. You can do this with a video card with a video output or an adapter for your PC and a image viewer with a slideshow mode or a presentation program. Or you could simply dump them to video tape with the in-camera playback and TV output that most cameras seem to have today.

Computer monitors still seem to represent the highest quality output mediums in terms of resolution and quality. I'd say some prints are almost as good, but a print, being a reflective medium, never looks quite as impressive as an image depicted on a good monitor, at least to me.

-- Gerald M. Payne (gmp@francomm.com), May 22, 2000.

I think there is some potentially dangerous inuendo here that needs to be halted. JPEG is NOT, and I repeat, NOT an archival file format. It is lossy, and each time you open and re-save, data is LOST, FOREVER! Don't waste your time scanning all your film, and then save as JPEG. You will be sorry.

-- Jason M. Kirk (jasonkirkphoto@hotmail.com), May 23, 2000.