What macro lens magnification and working distance do I need to copy 35mm slides on a Nikon D5100?

Question

I want to digitize a large number of mounted 35mm slides using a Nikon D5100 instead of a flatbed scanner. My current attempt uses a projector as a backlight source, with the camera aimed at the slide, but my Nikon 40mm f/2.8 Micro does not fill enough of the frame at the available distance.

The slide image area is larger than the D5100’s DX sensor, so I need to know what lens specifications matter here. Specifically, what maximum magnification and working distance are required to fill most of the frame with a 35mm slide image, and is there a better way to hold the slide at the correct distance than trying to work around the projector housing?

user15871 · Answer

Since the slide is 1.5x the size of your camera's sensor, you need a lens with a Maximum Magnification (MM) of at least 0.66 and a working distance of 8 inches (≈200mm). Working distance is the minimum focus distance minus the registration distance and lens length at full extension. Registration distance is the distance from the sensor to the lens mounting flange.

The MM for your 35mm f/1.8 is 0.16x, so it won't do what you need.

The MM for your 40mm f/2.8 Micro is 1.00x, but to get that maximum magnification you need a working distance of only a little over an inch (presumably it could achieve 0.66X at a working distance of around 4.5 inches which is what 1.5x the minimum focus distance works out to in terms of working distance), so it won't do what you need.

The MM for your 18-55mm f/3.5-5.6 is 0.31x, so it won't do what you need.

The Nikon 105mmf/2.8G AF-S VR Micro has a MM of 1.0x at a working distance of about 5.3 inches. If you do the math by extending the minimum focus distance by 1.5X the working distance figures out to about 11 inches.

The Nikon 85mm f/3.5G AF-S DX VR Micro has an MM of 1.0 at a working distance of about 5.1 inches. At 1.5x the minimum focus distance the working distance is about 10.75 inches.

So any Macro/Micro lens with a focal length of 85mm or more and an MM of 1.0x should do the job. Consumer telephoto lenses typically have longer minimum focus distances and MM in the 0.15x-.025x range and would not be suitable for what you want to do.

Please note that any imperfections (dust,scratches, etc.) captured by the scanner will also be captured by the method you describe in your question. The key to getting good slide reproductions, regardless of which method you use, is to clean them properly before you scan or photograph them. Shooting RAW will allow you more latitude in terms of color correction than a JPEG or even 16-bit TIFF from a scanner would.

If you only need such a lens for this project I would recommend renting one from a reputable rental house such as LensRentals.com or BorrowLenses.com. Set aside a weekend and do it on a three or four day rental.

What macro lens magnification and working distance do I need to copy 35mm slides on a Nikon D5100?

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