Lens Reversal technique for high magnification macro photography
Taken with a reversed 18-55mm kit lens
I have explained the lens reversal techniqueearlier. It is one of the techniques I like because of the reasons I mentioned before. I have been getting a lot of questions on reverse lens technique ever since I published it. Since it is becoming a favorite technique of photographers, I thought I should write more about it. I wrote the article by showing how to reverse a 50mm lens. But, it only gives you a 1:1 magnification. But, what if you want a magnification higher than that?
Taken with a reversed 18-55mm kit lens
So, in this article, I will explain how to take high magnification macro photographs using the lens reversal technique by reversing an 18-55mm kit lens. The tutorial is structured in the following way:
Lens reversal technique for high magnification macro photography — Reversing an 18-55mm kit lens
What is high magnification macro photography?
There are some of confusion about the magnification in macro photography. Most people get confused with the jargons like magnification ratio, life-size magnification, and numbers like 1:1, 1:2, 2:1, 3:1, etc. Or 1X, 3X, etc. But it is pretty simple. You need to know what these ratios mean when you read or do something about macro photography. Some of you might think, “why do I need to know the magnification ratio or all that mathematical stuff? If the subject is big enough in the photograph, then it would be fine” But, trust me, it will help you in framing and, moreover, that would help you improve your macro photography.
It is no rocket science. A 1:1 magnification (life-size magnification) is capturing the true size of a subject. Say, your camera has a 23mm sensor and if you photograph a subject which is 23mm long, it will fill the entire frame. And if you photograph the subject at 1:2 magnification, then the length of the subject would be 11.5mm in the photograph. Thus, a 2:1 magnification means you are capturing the subject twice its original size. And 1:2 magnification means you are capturing the subject half its original size. Some lenses like tamron 70-300mm offer 1:2 magnification where it let you focus a little closer than normal lenses to get that magnification. A dedicated macro lens gives atleast a 1:1 magnification. Similarly, 1X means the magnification is same as that of the real size of the subject, 2X means twice the size of the subject, and so on.
At 0.31m and 0.39m focusing distance, you can capture at 1:1 and 1:2 magnification respectively
What are the various methods for high magnification macro photography?
I had used reversed 50mm for macro photography before I started using the reversed kit lens. Like I have mentioned before, a reversed 50mm lens will only give a 1:1 magnification. Even though it was good enough, I wanted to try higher magnification. So, I looked up for various methods to take high magnification macro photography and found these:
Dedicated lens like canon MP-E 65mm.
Lens reversal technique with a focal length smaller than 50mm (or longer that 50mm, but I wouldn’t recommend that method)
Using extension tubes along with a dedicated macro lens or a reversed lens.
Lens coupling.
A magnifier like Raynox DCR-250/150 along with a dedicated macro lens.
Using microscopic lens (for very high magnification like 10X or more)
I decided to reverse my 18-55mm lens to take some high magnification macros because of the following reasons:
I could not afford a dedicated lens.
Drastic light loss if I use lens coupling or extension tubes.
I already had a kit lens.
Kit lens gives me the flexibility to change the magnification (1X -5X).
So, all I had to do was to buy the reverse ring for my 18-55mm kit lens and get started.
How to reverse an 18-55mm kit lens for high magnification macro photography?
I would suggest you to read my earlier posts on reverse lens technique since the steps are pretty much the same.
A DSLR with a cropped sensor. I haven’t tried reversing an 18-55mm lens on a full-frame DSLR. And I won’t recommend you to use it since at 18mm there will be vignetting (dark corners in the pictures). However, since the effective focal length of 18mm in a 1.6 crop factor DSLR is 34mm, you can reverse a lens with a minimum of 34 mm in a full frame camera. That would give the same magnification as 18mm in a cropped sensor.
A reverse ring for your 18-55mm lens. The filter thread diameter for 18-55mm lens is 58mm. So you need a reverse ring of that diameter.
Notice the 58mm filter diameter
An external light source. You need to use either your pop-up flash or an external flash as a light source to compensate for exposure loss. It is not just that simple to use the flash and get good results. There is so much to talk about lighting and it would make this post insanely lengthy. I will explain in detail about the lighting in high magnification macro photography in another article.
Some colored objects, flowers or leaves. This is for getting a colored background in the photograph. I will explain more about this when I explain lighting and exposure.
Next, I am going to explain how to use this setup to take high magnification macro photographs and how to get better results with a reversed 18-55mm kit lens.
How to measure the magnification of a reversed lens?
The usual question is, how do you measure the magnification once the lens is reversed. I have searched a lot about this. What I could find was that there is no absolute way to measure the magnification in macro photography. That is, there is no equation in which you could just put your parameters and get the magnification. All you could do is to use a ruler, take photographs at different focal lengths and then find out the magnification. However, I could be wrong about this. So if you have a proper method to measure the magnification of a reversed lens, then please share it with me.
F-number, magnification, and depth of field
The f-number, magnification, and depth of field are related. Understanding this will help you make a good image. However, this is most confusing part in macro photography and it is magnified in reverse lens technique and even more in high magnification macro photography. You will get confused about how to set the aperture or what aperture setting you should use at different magnifications to get sharp images. The usual mistake people make is ignoring the aperture settings when they use the reverse lens technique. And the result is an unfocused, blurred image. So you should know how to choose the aperture to get a proper depth of field at different magnifications. I can talk about this using some physics, mathematics and everything but I know it is boring and I don’t want to make you all dizzy and hate shutterstoppers forever. After all, getting good results doesn’t demand knowing all those stuffs. So, I am going to explain it as simple as I could do, even though there are some technical aspects which should not be overlooked. I hope you don’t curse me.
How depth of field is related to magnification and f-number?
Depth of field is simply the area of the image in focus. So, a shallow depth of field means very small area in focus and the rest of the image is blurred. The factors that determine the depth of field are aperture, the magnification of the subject, the distance between the subject and the sensor of your camera. Thus, by changing these, you can change the depth of field. But the story doesn’t end here.
High magnification macro photography needs a lot of light. This is because the effective f-number changes at high magnification as you need to use small f-number to get an acceptable depth of field. As I mentioned before, as the magnification increases, the depth of field decreases. At high magnification like 4X, the depth of field will be less than 0.2mm (that is the area in focus). So, to increase this depth of field, you need to use small f-number since narrow apertures increase the depth of field. But, even at f16, the depth of field is not good enough to get the entire subject in focus. In such cases, there are two things you can do: either focus an interesting part of the subject or use focus stacking method. However, it is not advisable to stop down beyond f16 since it causes diffraction which makes the image soft.
Now you might be wondering why at small f-numbers you don’t get very large depth of field even though you shoot landscape photographs at f16 and get the complete image in focus. This is because the f-number you set on your camera is not really the aperture setting at closer focusing distances (or when you shoot at high magnification). I guess you might be pulling out your hair now. Let me explain. The F-number you set in your camera is for infinity focusing distance. When the focusing distance decreases, the magnification increases. And when you focus at close distances, the f-number changes. Thus, the effective f-number is related to the magnification and f-number you set in your camera. You can see this by yourself. Set the f-number to f14 and change the magnification from 1X to 5X. You could see that the viewfinder gets darker when the magnification changes from 1X to 5X and vice versa.
Effective F-number =f-number x (1+magnification)
This is not a useful equation to calculate the f-number since there are several other parameters involved. This equation is just to give you an idea that f-number changes with magnification. Nikon users know this aspect more than Sony and Canon users since Nikon work on effective f-numbers. That is, Nikon changes the aperture as you focus closer while Sony and Canon does not. This is the case when the lens is in normal mount. In reverse mount, all brands work the same way.
Thus, high magnification results in shallow depth of field, so you need use narrow apertures (small f-numbers) to get an acceptable depth of field.
Changing the magnification while using a reversed 18-55mm kit lens
When the focusing distance decreases, magnification increases. Usually, lenses have fixed short focusing distance which is why you cannot take macro photographs using every lens. Dedicated macro lenses have mechanism to focus at close distances. In part 1 of this tutorial, I have shown you how the magnification changes with the focusing distance. The focusing distance is changed by:
Changing the focal length of the lens.
By an internal focusing mechanism. This technique is used in dedicated macro lenses like 90mm, 100mm, etc. When you focus closer using these lenses, the length of the lens doesn’t change.
So, at different focal lengths, you get different magnification. And the focusing distance changes, too. Thus, when the lens is in reverse mount, the focusing distance gets shorter when you change the focal length from 55mm to 18mm since the magnification increases.
Thus, the advantage of using a reversed 18-55mm lens is that you can change the magnification (1:1-5:1) by changing the focal length. Apart from getting different magnifications, another advantage is that you can find the subject to frame well. I will explain this in the next article.
Summary
All of this information might overwhelm you. So I thought I should give you the gist of this article. This article should give you:
A fundamental idea about depth of field, f-number, and magnification in high magnification macro photography.
Enough information to set the camera settings (aperture settings at various magnifications).
An idea about how to change the magnification when the lens is in reverse mount.
This post was last modified on September 18, 2019 3:04 PM
Vidhu Soman
Hi, I am Vidhu Soman, Editor of Shutterstoppers. I have been doing photography since 2010, and I co-founded shutterstoppers community in 2012. I love photography, writing, travelling, and reading. If you wish to contact me, send a mail using our contact form.