Using a Fluoroescent Flashlight to Scan 35 mm Slides on a Flatbed Scanner

Betty Winsett wrote in to say that she'd found a simple method for scanning slides using a fluorescent flashlight as a light source.  She said she just lays the flashlight on the slide and scans away.

Here's her web page on the subject:  http://www.afn.org/~afn11300/slides.html

Naturally I dug out the little Radio Shack model 61-2734A dual-mode flashlight (incandescent & fluorescent) that's been in a drawer for several years, popped in three new C cells, and gave it a try.

Sure enough, it works.  Here's a sample, a 35 mm slide scanned at 300 dpi and saved as a lo-res jpg:

You can see that the image is bright across the middle, and darker across the top and bottom.  That's because my flashlight's fluorescent tube is only about 15 cm in diameter, so naturally it lit up the middle of the slide.  A fatter tube would probably eliminate this problem.

All right, then, let's try a plastic diffuser, the same one I've used with a compact fluorescent desk lamp.  It made quite a difference, as you see below:

The diffuser produces much less difference in brightness, although it's still there and might be more noticeable in a photo with a plain background.

If plastic works, what about a sheet of white paper?

There it is--darker at the top and bottom.  The plastic diffuser is best.

What about the color differences in these images?  Unfortunately, none of these scans is identical to the original slide.  The center image has the steps, the house, and the yellow and pink shirts about right, but the bluejeans are too blue--too saturated.  The bluejeans look best in the top (no diffuser) scan.  My flashlaght's fluoroscent lamp appears to be a lot "whiter" than the scanner's internal lamp when I look at them together.  I think that influenced the color of the scans with no diffuser and with the paper diffuser.  The plastic diffuser itself looks "white" to me, but with it I get consistantly warmer scans, like the center image above.

Betty says she has found that a Tupperware top works well as a diffuser.  She says, "It's an OLD plain clear one."

I also tried scaninng with the slide at the center of the scanner, instead of in the corner, as Betty recommends.  I couldn't see any appreciable difference.

As with all slide scanning, it's essential to scan ONLY the film area.  If you scan some of the slide holder, the image will probably be much too dark.

So Betty's method works.  And it sure is simple!

Disadvantages?  Only two that I can think of.

  1. The lamp (mine) is narrower than the slide, so it illuminates the center of the slide more than the top and bottom.  A brighter lamp would probably make it feasible to add a better diffuser, to spread out the light so that the slide is lit evenly.
    2.            .
  2. You have to have a flourescent flashlight.
Why does the fluorescent flashlight work better than a compact fluorescent desk lamp, such as I've described in my "Improved Method ."  Because the flashlight (mine, anyway) produces the high voltage necessary to light up the fluorescent lamp at a much higher frequency than the standard 60 Hz desk lamp.  This prevents interference between the scanner's (60 Hz) internal lamp and the external fluorescent lamp--meaning that there's no likelihood of getting the striations that can appear when using a 60 Hz desk lamp.

I figured that out a couple of years ago, but--unlike Betty--never got around to trying a fluorescent flashlight.  How dumb of me.  And how smart of her!
 

Don Maxwell

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