Home Methods Double lens – Coupling lenses for macro

Double lens – Coupling lenses for macro

by Güray Dere

You are interested in macro photography, you want to try something different …

In your drawer lies various focal length lenses: 200mm, 135mm, 90, 50, 35 etc. Or at least there is a short/medium tele and a standard lens, let’s say.

If you don’t have a 1:1 macro lens, or if you want to shoot high magnification photos above 1X, you can consider methods such as using extension tubes, bellows, reverse lens. But if you want to do it with near-zero cost, try coupling lenses. It is possible to get amazing results with this strange looking technique.

49-52_ReverseRing
Macro coupling adapter. 49-52mm

All we need is a cheap adapter that connects the filter to the filter, which is used to mount the lens onto the other lens.

Step-up step-down filter size converter adapters

step-up-step-down-ring-adapter-set
37mm – 77mm filter step adapters

Again, it would not be a bad idea to get step-up, step-down filter diameter conversion sets for this technique as well as an investment for future needs. These can be sold individually or packed in different sizes in sets. We pay a much more reasonable price if we get it as a large set. For example, my set is made up of 16 parts and has both filter diameter enlargement and reduction adapters.

I have only one coupling adapter between 49mm and 55mm filter threads. I chose these values to mount the Pentax lenses such as 50mm or 28mm, which are used on Tamron 90mm. 49mm and 55mm are the filter thread sizes of these lenses.

When I want to couple different lenses, I can use cheap stepping adapters to convert their different filter diameters to 49-55 instead of purchasing separate coupling adapters for each lens.

These sets will help you with other things. For example, you will need filter diameter converters to use a single polarized filter in all of your lenses.

Which lens is better?

We need to choose two lenses for the application. There are some points to consider when determining which two are appropriate.

Sharpness

Double lens means we use two times more glass than normal. And each layer will steal from the sharpness and light transmission. But don’t be scared. Just select sharper ones. It is generally better to use prime lenses instead of zoom lenses.

Focal length – magnification

The focal lengths of the lenses are important. This ratio will determine the magnification. Add the ratio of the focal lengths of the two lenses to the magnification of the tele lens to find the total magnification.

So if we have a 100mm 1:1 macro lens, it has 1X magnification. When we mount a 50mm in front of it, 100/50 = 2X will be an extra enlargement. We’ll get 3X in total.

Aperture

The aperture value of the reverse lens, mounted to the front, should be in the wide-open position. It has to be a fast lens, having a wide aperture. Otherwise, you may face a high degree of vignetting. If you use a full-frame camera, vignetting will appear more quickly.

We can do a few things if we still have vignetting when the front lens aperture is wide-open.

  • We can replace the rear (main) lens with a lower focal length lens.
  • We can replace the front lens with a wider aperture lens.
  • We can replace the front lens with a higher focal length lens.
  • We can narrow the aperture of the rear (main) lens.

Sample photos

This time I did not want to take measurements with millimeter paper and do tedious calculations. I’m going to take direct sample shots. We will evaluate the magnification through consideration. As for the comparison, let’s start with a photo taken with Tamron 90mm at a magnification of 1:1.

A rose petal from the garden and live aphids on it will be our guests. Aphids are qute small creatures that even a true macro lens with 1:1 magnification may not be enough to take good photos of them. Microscopic magnifications like 10X are needed to fill the frame. Let’s see how they look in 1X.

Tamron 90mm 1:1 Aphid
Aphid in 1:1 magnification with Tamron 90mm

The 1X is quite inadequate to see the details. But the depth of field is fine with f11. We can see the whole insect clearly.

Pentax K 200mm f4

Pentax-K-200

I chose the Pentax K-200, an old manual lens with a focal length of 200mm as the main lens. It is quite compact so will not cause mobility problems.

Since it has a 58mm filter diameter, I first installed the adapter that reduced it to 55mm and then added the 55-49 coupling adapter. The reverse lenses, Pentax SMC M 50mm and Pentax SMC M 28mm, both have 49mm filter diameters.

Reverse Pentax M 28mm on Pentax K 200mm

The K 200mm lens is focused on its closest distance. The equipment looks a little long and bulky when we add the reversed lens.

Pentax-K-200mm-Pentax-M-50mm
Pentax M 50mm reverse mounted on Pentax K 200mm

I started with 28mm because I wanted to try the highest magnification. I expect a magnification of about 7.5X. I don’t have much hope because it is an extreme value, but let’s see the results now.

Reverse-Pentax-M-28mm-onPentax-K-200mm
Pentax M 28mm reverse mounted on Pentax K 200mm

Magnification is very high but the result is bad as I guessed. The f2.8, which is the widest aperture, could not prevent the vignetting. I used f16 on 200mm to compensate for a little bit. But the vignetting still remained (even it is an APSC camera) and the diffraction killed the details. Our photo looks like a watercolor painting. K 200 and M 28 simply cannot be used together.

Pentax M 50mm on Pentax K 200mm

The SMC M 50mm lens is both f1.7 and has a focal length of twice as much as 28mm. I feel it will not create a vignette. And we may be less affected by the loss of details due to diffraction if we use the 200mm lens at f11.

Let’s see what we get.

Aphid-Reverse-Pentax-M-50mm-onPentax-K-200mm
Aphid with Pentax M 50mm reversed on Pentax K 200mm

Magnification should be close to 5X. We got a better picture than 28mm. But it’s still not the quality I can accept. Perhaps the K 200mm is not a sharp enough lens. Let’s try the Pentax K 135mm f2.5, famous with it’s sharpness.

Reverse Pentax M 50mm on Pentax K 135mm

K 135mm had been good with Raynox and had produced nice macros. I guess it will work similar with a reversed 50mm.

Aphid-Reverse-Pentax-M-50mm-onPentax-K-135mm
Reverse Pentax M 50mm on Pentax K 135mm

This time it seems to have reached a reasonable magnification and again a reasonable quality with a nice framing.

Magnification is around 3X. If we are shooting in hand we should not exceed this magnification. Naturally, our depth of field is not enough. You’ll have to take a few extra frames and process unclear areas in the computer environment (focus stacking).

Result

I kept the aperture at f11 in order to increase the depth of field in the sample photos. It caused a loss of detail because f11 is too narrow compared to the level of magnification. Sharper pictures can be obtained if you set an aperture like f5.6 in the main lens and do focus stacking.

There was another lens I wanted to include in this article: Nikon El-Nikkor 50mm f2.8N. I was confident that it would produce much sharper images than Pentax 50mm. But my 40.5mm-49mm filter diameter adapter and the PK reverse lens adapter that I used in this lens are stuck together. I pushed my hand until I cut myself, and then I gave it up. Sometimes Chinese adapters can be very annoying.

My personal opinion is that the dual lens technique is not a choice. At least I can’t get close to the quality I want with my lenses. If you have to, testing lens coupling is pleasant, but the quality of the pictures taken with simple reversed lenses on extension tubes are superior. Have a set of extension tubes and read the article on reverse lenses.

You may find interesting

Leave a Comment