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Macro photography with 20X microscope lens

by Güray Dere

In those days of discovery, when I couldn’t find peace in macro photography and started looking for something different, I always had the same thing in mind: To get closer, to see more detail.

The very first of everything followed one after the other. Reversed wide-angle lenses, microfilm lenses and finally microscope lenses. It was very enjoyable to observe structures and details that I saw for the first time. After 3X, 5X, 8X, 12X, I had reached the limit with the Lomo 20X. I hit the wall right around here. This is where the sharpness ended. The photos I took were like mud. But it wasn’t only the lens that was to blame, it was the Pentax K-x body with lots of vibration. I ended the race and moved on, enjoying the comfortable magnifications.

20X is quite an extreme magnification. I used to see clear photos from the masters, even at 50X, but they were using space station-like setups. And there is a lack of subject material. Where is 20X needed? If we don’t work in a way that shows a certain detail, or if we don’t find a really small target (like a mite), there’s no point. Anyway, let’s move on to our lens.

The Infinity Plan 20X microscope lens, the subject of this article, was sent to me for testing by my friend Abdullah Tanık along with many other lenses (I thank him). The 20X was the first thing that caught my attention in the box with its bigger appearance than other microscope lenses. Then I locked onto the ∞ (infinity) symbol on it. You know how there are cartoon characters who have a $ sign in their eyes with the sound of a cash register? It was my first time seeing an infinity-type lens, the effect was hypnotic! The Infinity Plan 20X microscope lens, the subject of this article, was sent to me for testing by my friend Abdullah Tanık along with many other lenses (I thank him). The 20X was the first thing that caught my attention in the box with its bigger appearance than other microscope lenses. Then I locked onto the ∞ (infinity) symbol on it. You know how there are cartoon characters who have a $ sign in their eyes with the sound of a cash register? It was my first time seeing an Infinity type lens, the effect was hypnotic! We looked at each other for a while with the ∞ sign in my eyes.

Let us briefly recall microscope lenses

Microscope lenses in my inventory at the time of writing

Finite type microscope lenses

The most common microscope lenses are finite type lenses. In the early days they were all made this way. So they are relatively old and cheap lenses. But don’t underestimate them at all, they range from cheap and good quality to very expensive ones. You can understand that the lens is finite from the expressions like 160, 190 on them. This means that we can take this lens and put it in front of a bellows and start shooting immediately. If we extend the bellows to 160mm or 190mm, whatever it says, we get the fabrication magnification of the lens. If we put the Lomo 3.7X lens in a bellows opened to 160mm, we get 3.7X magnification. If we expand the bellows more, the magnification increases, if we shorten it, the magnification decreases. In this way we have the opportunity to capture the appropriate frame.

Infinity type microscope lenses

These lenses have a more modern design with a ∞ mark on them. To use them, we need to use another 200mm lens called a tube lens. There are special tube lenses as well as an ordinary 200mm lens or a zoom lens like 70-300mm can be used as a tube lens. Of course, the sharpness of the tube lens directly affects the result. It is preferable to have a good lens. As the focal length of the tube lens changes, the magnification changes. As in the bellows example, if we use a 10X infinity lens with a 200mm tube lens, we get 10X. If we use it with a 300mm tube lens, we get 15X, with a 100mm tube lens we get 5X.

Although zoom lenses are not very sharp, we have the chance to play with the frame by changing zoom levels.

For both types, the best, sharpest, vignetting-free operation is to use the lens at its own magnification.

20X infinity plan microscope lens

The tested lens is an unbranded 20X lens. Although we do not expect a high level of quality, since it is a new production lens, it must have benefited from some of the possibilities of technology. But it is not an APO lens, we should expect CA color distortion. And of course, the working distance is a matter of curiosity. Since the Lomo 20X was shooting at a distance of only a few millimeters, things were very complicated. Even lighting the subject at this distance is a problem in itself.

The lens has an RMS thread. Therefore, an RMS adapter suitable for the filter diameter of the tube lens will be used.

Infinity mikroskop lensi ve adaptörü
Infinity microscope lens and adapter

The RMS adapter Abdullah sent me has a diameter of 58mm. Luckily the K series manual Pentax lenses I have are also 58mm, so I can use the adapter directly.

The back surface of the RMS adapter is very wide and will be directly facing the glass, i.e. the sensor. Since it doesn’t have a matte surface, there is a possibility that it will harm the photo quality. To improve it, I cover the inside of the adapter with an anti-reflective “light trap”.

Pentax K 135mm f2.5 microscope lens on RMS adapter with light trap covering

The Pentax SMC K 200mm f4 will give me exactly 20X magnification, but I don’t trust its sharpness, so I’d rather use it with the Pentax SMC K 135mm f2.5. This lens is very sharp. It will give 13.5X magnification but it will be a lighter and sharper option.

Pentax SMC K 200mm ve SMC K 135mm lensler ile infinity tipi mikroskop lensi
Infinity type microscope lens with Pentax SMC K 200mm and SMC K 135mm lenses

Since the microscope objective will be very close to the subject, we will have problems especially with frontal lighting. To overcome this, I use a foam cup. The cup will act as a diffuser and the lower part of the cup at the end of the lens will work as a reflector, reflecting the light back to the subject.

Mikroskop lensi için difüzör / reflektör tasarımı
Diffuser/reflector design for microscope lens

I’m using the Pentax body as an example model, but the Sony A7II body with electronic shutter system will be used for shooting. This feature is so important in macro photography that if the body you have does not support it, you can immediately consider a body change.

Çekime hazır mikroskop lensi kurulumu
Microscope lens setup ready to shoot

20X test shots

When the magnification is 20X, you have to think about what to shoot. The target area will be as small as a pinhead. The working distance is short and the depth of field is extremely narrow. If possible, it is necessary to aim for flat-shaped targets, avoiding large(!) overlapping structures.

I decided to do the first experiment on a weevil beetle, the 1cm long beetle of which I have already published a full body photo:

Full view of the insect used in the shooting

I want to take a shot of the back of this one, to measure the working distance, to understand the magnification and the overall image quality. I need to see what I have before moving on to the actual shots.

Tek çekim 20X weevil sırt dokusu
Single shot 20X weevil back tissue

The working distance of the lens is about 5mm. That’s good for 20X. Magnification is very high. CA is also very high (we can’t see it in this photo because it has been cleaned). The overlapping feathers scare me. I need to choose a simpler target. The fly eye, a macro classic, is the first thing that comes to my mind. There are plenty of flies in the stock. I take one out and approach the eye.

20X sinek gözü tek çekim
20X fly eye single shot

And this one looks much better. The depth of field is very thin, but at 20X it’s not bad either. The fly’s eye is too big, it’s out of the frame. Each eye unit is visible with its details. Despite the correction, the colors that seem to be painted blue, especially in the bokeh areas, are CA distortion. But focus stacking and Photoshop CA correction function will save the situation to a great extent.

20X tek çekim crop
20X single shot crop

Here I’m cropping to show the state of CA degradation. These blue tones are the places that need to be corrected in Photoshop. Fortunately, it’s not too difficult because there are no blue tones in the whole photo. The whole batch can be edited together.

135mm (13.5X) ile yarım focus stack çalışması
Half focus stack work with 135mm (13.5X)

This time I’ll change the lens. When I put the 135mm on, the magnification drops to 13.5X. It will take a lot of testing with different models of tube lenses to understand the difference in sharpness and framing. My first impression is that the shot looks a bit better with the 135mm. The framing is also a bit better. 20X was too much. Now we see the fly’s eye from a wider angle(!). We see that the 20X lens adapts very well to a different magnification of 13.5X. Let’s take a closer look to perceive the detail. Let’s take a crop from this photo.

13.5X sinek gözü crop
13.5X fly-eye crop

After CA correction, the fly’s eye looks as above at 13.5X. Not bad detail for a full size crop. I’m starting to enjoy the lens. Let’s test it on a more colorful section. Our fly is a green fly. I take a shot from the dorsal region.

20X sinek sırtı
20X fly back

It’s going to be difficult to pick up the colors in this area. Also, the hairs are overlapping so I give up on continuing the shot. Let’s get closer to the root of the hairs and look at the detail through the crop before moving on to a full study.

20X sinek sırtı
20X fly hair crop

It’s really interesting to see it so close, even if it’s not very clear. But it takes courage to work in this area. I’ll leave this frame as a sample single frame shot and move on to the ant portrait I’ve been planning to recreate for a long time. My goal now is to make the work as complete as possible.

Ant portrait

Ant portrait was a work that made me feel all the challenges of 20X to the fullest. And I have to say once again what I repeated at the beginning of this article: I’ve reached the limit at 20X, with my current method. For the depth of the head of a tiny ant, I had to take 175 shots, each with a 2s exposure. And then I realized that if I were to include the right antenna, I would need about 100 more images. Because I was tired and I didn’t know what to expect, I stopped the process here and left the right antenna in the blurry field. Of course, with microscope lenses there is a very sharp transition from sharp to blurry. It looked like the antenna had broken off.

20X ant

175 shots is not excessive. That’s not what made me tired.

Precision rail

For the rail, I use one of the Newports, one of the best choices for macro. It’s an amazing rail that moves smoothly with more precision than I can feel. With the micrometer on it, 1 tick corresponds to a distance of 10 µm. If we use the Vernier scale, this precision can be adjusted down to 1 µm. But the problem is to rotate the micrometer with that precision.

I move 5-25 ticks between two photographs with reversed lenses.

When I use the Lomo 3.7X lens, my step is 4-5 ticks.

Step size is 1 tick on the Nikon 10X microscope lens

This time I had to go half or a third of a tick, holding my breath, with the smallest touch my hand could apply. So we’re talking about steps of 3-5 microns. That’s how shallow the depth of field is.


And if the depth of field is a few microns, how does ambient vibration affect this? Answer: In a devastating way.

I haven’t shot with microscope lenses in the living room for a while. Since the living room has a wooden parquet floor, even if I stand 1 meter away from the tripod, my breathing or even my heartbeat shows itself as vibration in the frame. Instead, I shoot in the hallway and use the stone parquet floor, where I can breathe comfortably. Actually, it was like this until today, but that’s over too. Because now I’ve magnified the vibration in the environment by 20X. I realized when I was watching the frame after shooting, I couldn’t get the sharpness!

I recommend watching the video below in full screen and HD.

Now you can imagine the cold shower effect I had when I realized this after 175 photos I had taken. Despite all that effort, the photo would not come out sharp. In other words, even if I had the best lens, it became clear that I could not achieve sharpness with these methods. The vibration is coming from the building and there seems to be no way to easily block it. They are probably caused by the central heating system working. 20X is something like that.

What kind of setup?

So what do we do? Give up at 20X when everyone else is taking 50X pictures? Of course not. Here’s the solution:

  • We will use a vertical setup mounted on the microscope body. The travel screws on the microscopes are much more sensitive than the Newport. Not only at 20X, but even at 100X.
  • We will cut a large marble block and attach anti-vibration rubber feet to it. Our mini-studio will be built on this. It’ll be like a solid rock.
  • We will get a powerful computer. I didn’t write above, but it’s not easy to process 175 photos with 24MP resolution and focus stack them. It can take hours. Storing big files is also a problem.

The third one is easy. But I think I’ll stay away from 20X until I get the first two.

Spider face

Before leaving the subject, I wanted to do one more test. For some reason, I made a difficult, even wrong choice and chose a tiny spider that I found dead that day. I say wrong because it is difficult to adjust color and contrast values on creatures with translucent bodies. The real difficulty is that the software has trouble finding the focus during focus stacking. When the structure is translucent, the difference between sharp and blurry images is very small. The software gets confused, and instead of getting that area from the sharp photo, it gets it from the blurry one. We lose texture and detail. The result is a problematic photo that is very laborious to process.

As a matter of fact, if I found a big spider and worked with 3X magnification, I would get a very clear photo in the same frame.

I also post this photo as an example, but I didn’t post it elsewhere because I didn’t think it was suitable in terms of quality.

20X tiny spider

I’ll leave the magnification race at 20X for now, but only for now 🙂

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