The How Zone

Macro Photography II

Lens Stacking

In the first Macro article I used a Diopter (Nikon 5T) to turn the 70-300mm lens into a macro lens. The 5T is a +1.5 diopter and the 6T diopter is a +3. What we will be doing in this article is gaining even more magnification by stacking a reversed lens. The formula for computing the diopter power of a reversed lens is:

1000mm / lens focal length

Using a 50mm lens we get a diopter value of +20. Quite a big difference from the +1.5 of the 5t! You can reverse other lenses as well, but I think you are better off reversing fixed lenses as opposed to zooms (like the D70 kit lens). Also, when reversing a lens you'll want to open the aperture up as wide as possible. Here are photos of the 50mm closed most of the way down and with the aperture wide open (we want all of the light we can get).

50mm closed aperture50mm open aperture

The reversed lens will go on the end of your primary lens. Ideally you would buy (make, borrow?) a threaded adaptor that fits the filter threads on both lens and keeps them aligned. For this quick and dirty testing and experimentation you can get by with taping the two lenses together. I put a little bit of tape on the ends of the 50mm so it won't scratch up the larger lens surface, a bit of clean felt would work even better.

Reverse lens mating Assembled micro setup

That's how the two lenses look when mated and taped together. If you are paying close attention you might be wondering about the screw sticking out of the end of the 50mm lens. File this under live and learn: I was using the screw to force the aperture wide open. Turns out that this old lens has an aperture dial and you don't have to use a hack to force the aperture open. If your lens doesn't have an aperture dial, you'll need to rig something up.

Also, one more note: the tape on the side of the lens is for "locking" the focus in place. This, ahem, cheap lens tends to change focus and zoom when you point it straight down...something about gravity and loose gears and not expecting a 50mm wart no doubt.

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