Digitizing 35 mm Slides

Posted by Dan on Mar 20, 2013 in Blog | 1 comment

In June 1970 I completed three months of counter-insurgency and Vietnamese language training at the U.S. Naval Amphibious Base, Coronado, California, and flew across the Pacific to Danang, Republic of Vietnam, and from there by helicopter to Coastal Group 12, a remote outpost of the Vietnamese Navy, to serve as senior naval advisor to Lieutenant Loc, the commanding officer of the base.  Coastal Group 12 was located in a circular fort built by the French near the village of Thuan An, where the Perfume River flows into the South China Sea.  To the west is Hue, the ancient capital and site of some of the bloodiest fighting during the January 1968 Tet offensive.  To the east, between Coastal Group 12 and the South China Sea, is a barrier island called Tan My, site of the in-country rest and relaxation (“R&R”) facility for the U.S. Army’s 101st Airborne Division.  Given its proximity to this R&R center, Coastal Group 12 was one of the most secure Vietnamese naval bases.  As luck would have it, however, after one month at Coastal Group 12 I was transferred to Coastal Group 14, located at the mouth of the Cua Dai River about 25 miles south of Danang and 5 miles east of Hoi An, where I spent the next 11 months in much more exciting surroundings. During my year in-country, I took about 160 photographs using Kodachrome film, the processing of which results in 35 mm color slides.  Those slides have been stored in a metal box for 40 years.

Consistent with the reputation of Kodachrome film, when I looked at the slides recently, I found that most of the slides are still as good now as when they were first developed.  For about the last five years I have been thinking that I should digitize them.  The question was, how best to do it? I decided to create my own image capture set up using a Canon 5D Mark II 35 mm DSLR camera equipped with a 100 mm macro lens and an LED flood lamp rated at 5000°K color temperature.  The Canon 5D Mark II is equipped with a full frame, 21 megapixel sensor that is approximately the same size as a 35 mm slide image, so, when using a macro lens, the resulting image ought to have very high resolution.  The image capture set up is shown in the photograph below.

This image capture set up works very well.  Here is the process.  First, with the room lights off and the flood lamp turned on, I inspect the translucent Plexiglas through which the light passes to make sure it is clean.  If I see dust or lint when looking through the camera viewfinder, I clean the Plexiglas.  I also check the camera mirror and sensor to make sure the dust is not inside the camera itself.  Next, I insert a slide in the slide holder and view the image through the camera viewfinder to check alignment and to inspect for dust again.  If I see dust, then I remove the slide, vacuum it carefully, return it to the slide holder, and inspect again.  Once the image as seen through the camera viewfinder passes inspection, then I adjust the shutter speed and aperture, if needed, for optimal exposure and click the shutter release cable to take the picture. Capture is instantaneous, and the image is displayed on the camera’s display screen.  The display is set to show both the image and its histogram so I can confirm that the exposure settings were appropriate.  After about 50 slides have been have been captured (in Camera RAW format), I remove the compact flash card from the camera and transfer the image files to my computer. (I could tether the camera directly to a laptop and avoid the compact flash intermediary storage device.)  Then I use Adobe Lightroom and Adobe Photoshop, if needed, to process the images.  The final images can be delivered in a variety of digital formats, including Camera RAW, uncompressed TIFF, and JPEG. The steps in image processing are illustrated and explained below using a photograph taken from the perimeter of Coastal Group 12 in July 1970.

• Initial capture.  This is the image as captured by the camera using the macro lens.  The dark border is the cardboard slide frame surrounding the transparent film.

• Horizontal alignment.  The Adobe Lightroom rotation adjustment tool is used to align the horizon properly.

• Cropping.  The Adobe Lightroom cropping tool is used to crop out the slide frame.

• Spot removal.  The Adobe Lightroom spot removal tool is used to remove lint that escaped detection prior to image capture.  If you expand the image above, you can find a piece of lint in the sky in the upper right quadrant.  In the image below, this lint has been removed.

• Exposure adjustment.  The white balance has been adjusted and the exposure brightened to make the image consistent with the bright tropical sunshine that I remember so well, and the shadow detail has been brightened also using the exposure sliders available in Adobe Lightroom.

• The value of high resolution.   There is a reason, of course, for seeking high resolution.  If we are going to be projecting digital images on a screen for an audience, or if we are going to be making photographic prints up to 20″ x 30”, then we want the digital images to be as sharp as possible.  The image below is about a 5x magnification of the image above.  The resolution of the detail in this scene is still quite good.

This entire digitizing process is fast and efficient, and it produces excellent results.