Macro photography - Part 3: Reversing a lens

Young hellgrammite larva photographed with a reversed lens.

Why would anyone consider reversing a lens?  It seems like an insane thing to do, but it is actually one of the best ways to do extreme macro photos.  The outlay of capital is also low, but there is quite a learning curve to it, and you have to have a camera that can work without a lens attached.  The good news is that there are a lot of DSLRs about that will go this - all my D7000 series cameras do fine with this.

What is needed is a good prime lens with a manual aperture - I use a 50 mm for most of my work.  It doesn't even have to have the same mount as your camera because it is the filter thread that attaches to the lens reverser; the bayonet mounting plate faces the subject.  It should be a high-end lens, totally manual everything, with a minimum aperture no lower than f/1.8.  One of the best lenses out there for reversing is an enlarger lens that is ridiculously sharp; its minimum aperture is f/2.8.  I sometimes use a 55 mm f/2.8 AI micro Nikkor lens.

The good news is that all these components are relatively inexpensive.  A reverse ring is under $30.  An old manual focus/manual aperture lens should be easy to find and less than $100.  If you want to get closer, you can consider a lower mm lens or a set of extension tubes.  And the good news here is that they don't have to auto tubes, manual ones work fine.

If you reverse a 50 mm lens on a full frame camera, you end up with a reproduction ratio of about 1:1.  This is increases to 3:2 (1.5:1) if you use a crop sensor DSLR camera with a crop factor of 1.5.  Here's the weird thing.  Longer focal lengths produce less magnification than shorter focal lengths, so a 100 mm lens only gives about a 1:2 reproduction ratio and a 35 mm lens produces about a 1.4:1 reproduction ratio.  Going ever wider, like a 28 mm, produces reproduction ratios approaching 2:1.  This becomes 3:1 if using a crop sensor camera instead of a full frame one.

You can increase that magnification significantly by using extension tubes or bellows.  The above image (top right inset) shows a DSLR camera with a bellows attached to a reversed 50 mm lens.  Such combinations can easily produce reproduction ratios well over 4:1.

It is very important to consider working distance.  Unlike using a lens the normal way, the working distance between the end of the lens and subject is constant.  It is also incredibly close at somewhere between 44 and 47 mm, depending on what camera brand you use.  You cannot use a mirrorless lens in the same way because the working distance is less than 20 mm and there is no manual control of the aperture.

When buying a reverse ring, you have to consider the lens' filter size.  My 50 mm lens has a 52 mm filter size, so my reverse ring is for a Nikon camera with a 52 mm thread adapter.  If the lens' filter size is different from your reverse ring, you will need a filter adapter.

Then there is the how to part, which is another blog.

Thanks for reading.

Eric Svendsen     www.ericspix.com