Before I went digital, I accumulated thousands of slides and negatives, and of course, now want these treasures available as bits.  Here, I compare seven methods to transfer slides to digital.  The images below were captured with ordinary due care, lightly color corrected, then cropped to equivalent coverage, but otherwise not manipulated.  The high resolution original was then scaled to fixed size for presentation here.  Click on the individual images to get the full resolution original.
 

Flatbed Scanner HP Scanjet 6200C It's tempting to use a simple attachment to a flatbed scanner to scan slides.  This attachment is made by HP and is basically a mirror box which directs light around to the back of the slide, so the scan sees mostly transmitted light instead of reflected light.   The mostly is an important consideration;  Since lots of light is hitting the slide in the normal reflective path, dust on the near side of the slide or on the scan bed appears as white spots  rather than black spots, and white spots are a lot more visible than black.  At 1200 dpi, scans seem pretty soft and lack contrast, even after pre-scan adjustment.    The mirror box looks like a pretty generic design, but it is not.  The specifications are precisely tuned to the geometry of the scanner; it doesn't work even with close family members of the scanner it is designed for.	Flatbed Scanner Microtek 9800XL Its also interesting to try a relatively expensive scanner with a correspondingly expensive transparency adapter.  This mictotek scanner costs approximately $1800 with the transparency adapter, and claims to scan at 2000 dpi.  However, the detail available is less than the detail achieved by the HP scanner at 1200 DPI. One advantage of this scanner/adapter combination is that it can scan large transparencies, presumably up to the full size of the scan bed.	Projector based copier                                                  Direct copy attachment Digital Camera Nikon Coolpix 990 A Digital Camera can be used as a quick and dirty way to digitize slides.  At 2048x1600, that's roughly equivalent to a 1800 dpi scan.  Not bad, , but I've never been very satisfied with the results.   The shot on the left was taken using my projector and a device called Slide-To-Photo.  The company that made Slide-to-photo seems to be defunct, but similar products probably exist, or you could build your own. Slide-to-photo is a frame that links camera and projector in a mechanically stable way, so once set up, you can iterate next-slide/shoot very quickly.   This approach is  generic enough that it will probably work with just about any projector and camera (good) but the copies are only as good as your projector lens (many projector lenses are amazingly bad) and it's impossible to avoid some degree of keystoning because the projector, screen, and camera cannot all be in a line.  Some models of carousel projectors have a rear-projection "preview" screen that could be used similarly. The default lens sold with most slide projectors, including typical Kodak carousel projector zoom lenses, is really bad.  If you're using this kind of consumer-junk lens, expect lower quality than seen in this sample.  I spent an extra $150 on a good lens for my projector. The shot on the right was taken with a slide holder that mounts directly on the camera, using the Coolpix macro capability to focus directly on the slide.  The downside of this rig is that you still have to deal with your slides one at a time, and whatever attachment you use will probably be specific to your particular camera.   The upside is that since your camera points directly at the slide, without additional lenses or focusing screen, the quality is maximized. Setups like this have to be carefully matched to the mechanical and optical properties of the camera, so be sure to search for something that is known to work with your camera. I haven't tested this, but it looks like a reaonable packaging of the camera-plus-slide-holder into a dedicated USB device.  This particular device is being sold for about $100 under a number of different names.  Similar or improved versions are bound to appear. Typical problems with any camera based conversion are excessive contrast and odd color balance, which require a lot of tweaking in photoshop to fix..  It's also surprisingly difficult to get the framing right using only the camera's LCD to aim.  This transfer actually looks better than most.  I should also note that the Coolpix' options for adjusting exposure, contrast and white balance are not particularly useful in this process. Finally, the players in this camera-add-on market come and go.  For example, both of the specific products shown here no longer exist - search the web for current products.		Consumer Transparency Scanner Minolta Dimage Scan Dual This is the result from a scanner designed for the task, but priced suitably for home use..  I think it speaks for itself, even at the resolution you see here.  The original scan is at 2400 dpi. You probably can't find a scanner this old any more, or if you do it will be very cheap.	Prosumer Transparency Scanner Minolta Dimage Scan Elite This is the result from a better scanner, but still priced suitably for home use..  The Scan Elite is slightly higher resolution, slightly better density range, slightly faster, and incorporates Digital Ice technology to remove dust.  The original scan is at 2820 dpi. The price/performance ratio of scanners in the consumer price range is improving rapidly,  but using this kind of equipment is still time consuming and requires lots of practice to get good results.	Professional Scanner Nikon Coolscan 4000 This is the result of a professional scan by Larsen Digital, using expensive equipment, and scanning at maximum 4000 dpi resolution.  Note that professional scans are not automatically at such a high resolution - you probably have to pay more. For all practical purposes, 4000 dpi  is all the resolution there is on a 35mm slide, but there is still room for improvement in color and dynamic range, even at this level of technology.
size normalized	size normalized	size normalized	size normalized	size normalized	size normalized	original size

ICE makes a difference You could spend a lot of time cleaning and cleaning and cleaning your slide, or using photoshop on the scan to get rid of these little pieces of crud, but the digital ICE technology incorporated into newer transparency scanners is almost like magic.
Detail, without ICE	Detail, with ICE

Final Notes:

•  It's never too soon to start preserving your analog photos, and it may already be too late.  In the process of scanning my archives, most of which have been in unopened boxes or untouched negative sleeves for up to 40 years, I found:
• Negatives which had glued themselves to their sleeves.
• Strange snowflake-like artifacts on negatives, which were NOT present on the original prints made from them.
• Slides which were developed by drugstore-type services, which had faded very badly, where the same film type processed by other processors at the same time were still fine.
• Remember that resolution isn't everything. Color and contrast are equally important, and depending on the intended use of your scans, any of these methods might be ok.  However, the best results are clearly obtained using slide scanners.
  
• The Achilles heel of this process is cleaning. Literally microscopic specs of dust become asteroids when scanned at 2400 dpi.  Newer scanners which use ICE technology to remove the dust are wonderful - but remember that ICE is only papering over the crud, not removing it.   Except for slides with serious gunk (such as fingerprints) I recommend cleaning using compressed air, an antistatic brush, and careful attention.  Even a quick blast helps a lot.   For slides with serious problems, I use Pec-12 and Pec Pads.  They're not miracles either, but they help.   The best solution, of course, would be to never get your slides dirty, but that's not a realistic prospect.  Even slides that have never left their box seem to accumulate dust from somewhere.
  
• Converting color negatives is much harder due to the orange mask and compressed dynamic range.  Flatbed scanners and Digital cameras are just not adequate.
  
• There are good reviews of many types of scanners at Imaging-Resource.com
• Prices and services for scanning vary wildly.  Lars Bell has compiled an excellent spread sheet of professional scanning options.
  

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