Spring 2014 UPDATE: Don Oystryk has sent in some tips on slidescanning technique and high contrast image processing (HDR).
Fall 2012 UPDATE: Read what others say about this technique


My tool for getting good, fast images of
35mm slides with a digital camera and a
$25 slide viewer.

Transferring 35mm Slides to Your Computer
Quickly and Easily
April 2006

Anyone beyond a certain age or who has inherited photos from their parents will have a quantity of 35mm slides they want to get into their PC. I don't know what the appeal was for 35mm slides back then, maybe it was dropping them all into a Kodak Carousel projector and just storing the loaded cartridges for ready use, but whatever the reason my dad left me 100's of slides.

I have worked out a simple technique for getting adequate quality digital images of 35 mm slides using a typical digital camera and a cheap camera store accessory. But first let me tell you about the dead ends I investigated before finding my own solution.

Background

There are several ways to get slides into your home computer. Here's a brief run-down:

Technique Description Cost
1. Professional service Your local camera shop can scan in your slides for you $10-25 per slide
2. Slide scanner You can buy your own dedicated slide scanner $300-1200
3. Use your own flatbed scanner There are several techniques to do this (see below) none
4. Use a digital camera Use a slide previewer to illuminate the slide and snap a photo <$25
5. Use a digital camera Project your slides onto a screen and snap a photo Projector & screen

Options 1 and 2 are prohibitively expensive for me, especially since the low-end slide scanners don't get very good reviews. I'm sure if your slides are really important, you'd want to buy a scanner. But my slides are just family stuff, and many have deteriorated so much from age that they're pretty marginal.

Flatbed Scanner

Since I spent so much time trying this approach it seems worth a passing mention. Ultimately I found it unsatisfactory, but there are several low cost approaches you can try. The gist of them all is to illuminate the slide from above, and scan at 1200 dpi. The illumination can come from mirrors, folded paper, handheld fluorescent, etc. Here are links to some web pages:

Mirrors Two mirrors at special angles reflect the scanning light back through the slide http://www.sci.fi/~animato/scanning/scanning2.html
Paper A triangle of white paper can bounce enough illumination back to light the slide. http://www.abstractconcreteworks.com/essays/scanning/Backlighter.html
Lamplight A handheld fluorescent light is placed on top of the slide. http://www.afn.org/~afn11300/slides.html

The "Mirrors" approach was invented by Hewlett-Packard. They used to include a little triangular mirror gadget in with their scanners. It seems like a good idea, but it never worked for me. I'm not sure why, perhaps some scanner bulbs shine a narrower band of light than others.

Here's what the scanner sees.

The "Paper" gadget is shaped just like the HP mirror device but is simply folded of stiff white paper. I had tremendous success using this scheme on on old large size black & white transparencies. You can make the paper triangle any size you need. I had less luck with modern, small format color slides.

The "Lamplight" idea sounds promising, and my old Microtek scanner even included a light with it. But in my experience the results are very poor. If you buy your own fluorescent, try and get one that has natural colors.  A typical cold white fluorescent will make your slides look blue (more on this below). But you can try and correct in PhotoShop or something if you have to. Some old slide printing technologies turn blue all by themselves.


Use Your Own Camera

I was partly inspired to try this approach by the old Shotcopy device for using a video camera to capture slides, and by an even older film camera duplicating device. It consisted of a tube that attached to the camera body at one end and had a little slide holder at the other. The user would adjust his camera focus accordingly, point the camera at a nice light source, and snap a photo.

The Shotcopy is a wooden stand for
your slide and video camera
.
When attached to your film camera, this can be used to copy a slide.


Why not use this approach with a modern digital still camera? At first glance this might not seem like such a great idea. Won't your scanner give better resolution? Well a little analysis will show that even an older 3 Megapixel camera is in the same ballpark as the scanner, and a newer camera can do better. Here are the numbers:

Flatbed scanner 35mm x 23mm slide at 1200 dpi 1644x1080 pixels
3 Megapixel camera Camera in Macro mode, 2400 x 1800 image setting Cropped to 1395 x 927 pixels

The wild card in what your camera can do is how close your macro setting will focus. Part of my 2400x1800 photo is just the cardboard slide frame and gets cropped. But I have found even these cropped images are suitable for use as a screen saver or printing out as a 4"x6" print. In addition, this technique is very fast, and you really process a lot of slides in a hurry.

[ NOTE: A variation on this scheme, using a screen and projector instead of a slide viewer was suggested by Jack Clark. See Jack's email to me here. ]

There are two tricks to using your digital camera in this manner. First, you must have a nice lighting source. I have found that camera stores carry a variety of small slide previewers. My first one used a bright white fluorescent bulb. At the time I didn't realize that this gave my slides a blue tint. I thought the film had just deteriorated. For my second light I shopped more carefully and found one whose lamp is adjusted to give natural colors. Either of these gadgets cost less than $25.
Small battery-powered slide viewer. Plain white
fluorescent light
Gepe G-5002 Slide Viewer uses a cold cathode
lamp (5000K) to give correct color


Second, you must have some method of suspending the camera above the slide previewer, at the closest distance your macro setting will focus, or until the image fills the camera view. After MUCH experimentation I landed on this very simple scheme. It uses the camera 's built-in 1/4" tripod mounting screw hole to hold the camera. You have to saw off the Gepe viewer's folding magnifier.


The base consists of a plain block of wood, some velcro,
and a piece of aluminum the right length so your
camera is a close as it can focus to the slide.
Here it is with camera and slide viewer
installed. (Click to enlarge)


You will also find it useful to velcro down the slide viewer and tape some strips of cardboard on the viewing area of the larger models so each slide can be quickly placed in exactly the same spot each time. The Gepe viewer has built in positioning ridges. If you're shooting several hundred slides it really pays to have things locked in place.

So how does it work? Here's an example. The original below left is a 300 dpi scan of a 4"x6" print from Kodak. On the right is a digital shot of the 35mm slide of the same scene made with my Fujifilm FinePix 40i. This camera has the additional advantage of having a remote trigger, so there's no danger of jiggling the camera as I take the shot. The Fuji's color differs, but beyond that I don't see much difference.

4"x6" Kodak print scanned at 300 DPI on a flatbed
scanner. (Click to enlarge)
Picture snapped with Fujifilm 1.3 megapixel
camera. (Click to enlarge)

This time with a Canon Powershot A70. (Click to enlarge)
I repeated the experiment with a newer Canon Powershot A70 four megapixel camera, but although the colors are brighter, the actual image size turned out to be the same.

I'm sure newer 5 and 8 megapixel cameras can do better.  

Please send me your own experiences in scanning old slides!


Charles Hall
charles.p.hall@gmail.com