What lens should I use to be able to fill the frame with a mounted 35mm slide at 12 inches?

Question

Objective:

Digitize thousands (~7500) mounted 35mm slides as quickly as possible (without using a paid service), about 1,000 before Father's Day.

Equipment:

Kodak Carousel 750H Projector Nikon D5100 Nikon 35mm f/1.8G AF-S DX Lens Nikon 8-55mm f/3.5-5.6 AF-S DX VR Nikkor Zoom Lens Nikon 40mm f/2.8G AF-S DX Micro NIKKOR Lens

Background/Failed Attempt:

I own a CanoScan 9000F MKII (flatbed scanner capable of 9600dpi film/slide scanning), but the very slow speed combined with having to accept either lots of uncorrected imperfections (40-50 year old slides) or even worse "corrected" imperfections lead me to look for another solution.

I had all of the above except the 40mm Micro Lens. I had seen some fantastic results from numerous different individuals online that had successfully used a dslr w/ macro lens and a projector (optics removed, diffuser added) to digitize their slide collections. For clarity, the camera lens is aimed directly at the backlit slide.

After doing my best to copy the successful setups, the results were poor at best. The biggest problem is that the 40mm lens was a mistake-- it can't even begin to fill the frame at 8 or so inches (integral plastic housing where the projector's lens would normally be takes up the majority of this distance). When focused, the slide occupies less than one third of the image. Amazingly, the images look good, but 1/3 times my 16.2 mp isn't good enough.

At this point I am gun shy to rush out and buy another lens without doing my homework and knowing absolutely it will work (can't afford to lose the time or the money). I know there must be a simple set of equations that would answer my question, but knowing that my camera has a cropped sensor (DX) doesn't help me at all.

Question (restated, finally):

What lens is capable of filling the frame with a subject the size of a 35mm slide (film part only) on a Nikon D5100 at a distance of approximately 8" (PLUS the length of the lens) while keeping the depth of field at a minimum (thinking 2.8)?

If there is any additional information I can provide that will help, please let me know. My Dad is getting old, and I want this to be a special Father's Day for him.

Thank you very much.

Answer 1

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.

Answer 2

I've recently undertaken a similar project and found that the Nikon ES-1 slide copying attachment is a great piece of equipment. It screws on to the front of a lens and holds a slide parallel to the sensor/film plane, and also provides a diffuser to help adequately light the slide.

I'm using a D800 (full frame) and 60mm AF-S G lens and mounting the ES-1 to it with a 62->52mm step-down ring. (The 60mm lens has a 62mm filter ring; the ES-1 is 52mm.) Nikon's 40mm macro lens on a crop sensor body like the D5100 is equivalent to 60mm on a full frame, and the 40mm lens also has a 52mm filter thread, so the ES-1 will simply screw right into it.

The ES-1 is sitting much closer than the 8 inches you were aiming for, but that's not a problem because the lens actually does focus closely enough for the ES-1.

The diffuser on the back of the ES-1 is effective at diffusing light, but you still need a light source. You can line up the camera with your projector and take advantage of its light. (I'm using an external flash to light the slide, pointing back at the camera.) Alternatively, you can just point your camera out a window at the sky -- color balance won't be perfect, but you'll get enough light to be able to adequately capture the slide.