Photographing Insects: Choosing a Macro Lens
Comparing the two Canon 100mm macro lenses
After using my kit lens and extension tubes for two months it is time to get a true macro lens. Here I talk about my requirements and compare the new Canon RF 100mm 2.8L Macro with its much cheaper predecessor, the EF 100mm 2.8L Macro. Which one should I buy?
An adapted version of this article has appeared in my free book My Journey into Insect Photography that you can download here.
Disclaimer: This is not a full review of the lenses. There are many of these on the web. I only look at the lenses from my personal perspective and for insect photography, in particular handheld. Macro lenses are often also used for portrait photography, product photography, and even as general prime lenses. Moreover, I use them on a modern APS-C camera, which might be different than on other cameras.
I apologize for this being a rather long article. But I wanted to do a thorough job.
Requirements
From the experience over the past period I derived the following requirements for a macro lens:
At least 1x1 magnification. I like to shoot small insects. With my current setup they still tend to become too small in the image and require a large digital crop. A 1x1 magnification of the lens is actually 1.6 for my APS-C sensor, so that is already very good. Anything more is a bonus.
High-speed autofocus. Contrary to the belief of many macro photographers, I use autofocus most of the time. But for this to work smoothly, the autofocus has to be very fast and precise. So no manual lens for me.
Reasonable working distance. With my current setup I sometimes have to get as close as 3 cm from the lens to the insect. That can scare the insect away, and I often bump into things with the camera and diffuser. So I want a lens with a longer focal length, like 85 mm or 100 mm, to get a reasonable working distance.
Excellent central image quality. As I use an APS-C camera, image quality in the corners is not important, as the corners do not show in the image. But, because of the high 32MP resolution in the area in the center, excellent central image quality is essential.
The following aspects are nice to haves, but they are not essential:
Image stabilization. Because I use flash all the time, image stabilization is not important to avoid camera motion blur. But it does help to get a more stable image in the viewfinder and to focus more easily.
Non-extending. I don’t like lenses that extend when focusing. I use a flash diffuser on the lens and when the lens moves, that diffuser moves as well and might bump into the plant with the insect. Also, I sometimes rest the front of the lens on something.
Low weight. I like to travel light. So I don’t like heavy lenses.
Possible choices
My requirements limit the possible choices considerably. Having autofocus rules out all the great Laowa lenses and many others because they are manual. B.t.w., an addition problem with fully manual lenses is that the excellent manual focus guide of Canon cameras no longer works.
That basically leaves the Canon and Sigma lenses. The Sigma 75 mm has a minimal working distance of only 6.5 cm, which is a bit small. So the 105 mm might be a better choice. Both Sigma lenses are considerably cheaper but reviews say that they are slightly less sharp and the autofocus is less good. So instead I decided to rent and test the two possible Canon macro lenses: the Canon RF 100mm 2.8L Macro and its predecessor, the EF 100mm 2.8L Macro using an adapter, which I now abbreviate as RF100 and EF100.
For the EF100 you can easily get a good used one for less than 700 euro, while the RF100 costs 1500 euro (used ones are not really available yet). So there is quite a price difference. Is that worth it?
Feature comparison
Considering my requirements, the following follows from the specs:
Magnification: The RF100 has maximum magnification of 1.4, while the EF100 has a magnification of 1. That is a considerable difference. On APS-C cameras these become 2.24 and 1.6, respectively.
Autofocus: Both have fast and accurate autofocus. Reviews say that the RF100 is even better and faster than the EF100.
Working distance: At 1x1 magnification, both are above 10 cm. The RF100 has a working distance of 9 cm at 1.4 magnification.
Central image quality: Both are L quality lenses, so image quality is excellent, in particular in the center.
Both have image stabilization, are non-extending, and have a similar weight of around 700 gram (if you add the weight of the adapter to the EF100), which is on the high side.
There are some other features that are less important to me. For example, both are weather sealed, but I don’t like photographing in the rain, and insects are normally invisible in wet, cold, and/or stormy weather.
Look and feel
When adding the adapter to the EF100, both lenses have about the same length and weight. The RF100 clearly looks more modern. It displays all information in the camera, not on the lens. In particular, when using manual focus, the RF100 shows the focus distance and the magnification factor in the viewfinder, while the EF100 does not. For the EF100 this can be a problem because there is no tactile feedback on the position of the focus ring. So while looking through the viewfinder you do not know whether you are at maximal magnification.
The RF100 has this weird Spherical Aberration control, which seems useless for insect photography. Who wants dreamy looking insects? So I set it to 0, with the lock on. It also has the extra control ring that all RF lenses have. That can be handy. I normally set this to exposure compensation. But as I use flash for the insect shots, that is rarely used there.
The EF100 is a bit more noisy than the RF100. You clearly hear the autofocus and also the image stabilizer. I find this a bit annoying but I guess you get used to it. At least you know the lens is working for you. The RF100 is almost completely silent.
Focusing
I went out for three days, taking insect pictures with both lenses at different locations. Using the lenses was easy. Actually easier than using my kit lens as I no longer had to set the focal length. The weight of the lenses was something to get used to, but soon I no longer noticed. They are not too heavy and give a solid feel while taking shots.
I used autofocus most of the time. I did notice some differences here. The EF100 is a bit slower and sometimes had trouble to focus very closely and kept moving back and forth a little bit. This was in particular a problem when there was some wind. The EF could not keep up with the changes in distance due to the wind. The RF did a much better job.
I was a bit disappointed with my keep rate for both lenses. But then I realized that with these lenses I was using a larger magnification than with my previous kit lens. And that considerably reduces the depth of field and, hence, the chance of a sharp image at the correct place. I learned that it is often better to go for a bit of digital crop to get a better depth of field.
Both of these lenses have a maximal aperture of 2.8, which is much wider than the kit lens I used before. Because the camera focuses with the lens wide open, the depth of field you see during focusing is very small, and considerably smaller than with the kit lens. Initially I thought that the focus of these lenses was worse, but that was obviously not the case. When taking the shot, the actual aperture is used, giving the expected depth of field. After a bit of practice this was actually a positive. Because only a small area is in focus while focusing, you have to be very precise, leading to better shots.
You can use the DoF preview button on the front of the camera to see the actual depth of field. However, this unfortunately does not work with autofocus. With manual focus though, it works great. Even the focus guide works while holding that button.
Image stabilization seems to work well in both cameras, but it is clearly audible on the EF100 while being almost completely silent on the RF100.
Image quality
This is very difficult to compare because I took different shots with the cameras. (I did not want to switch lenses too often.) In general, the quality was better than the shots I took before with the kit lens and extension tubes. For my earlier shots I often needed to do some sharpening in post processing to get them sharp enough. With the new lenses this is no longer necessary.
Doing some pixel peeping on controlled shots, for both lenses sharpness is very good until F11. F16 is still doable, but F22 is not good enough, especially if you are going to use digital crop. I had the feeling that the RF100 was slightly sharper than the EF100 at F11, but this can be due to many aspects other than the lens.
Magnification
In the field I noticed I do not really use the maximal magnification. When photographing handheld this is almost impossible, unless there is absolutely no wind. And even then the depth of field becomes so small it is better to use a smaller magnification and a digital crop later. So the advantage of the RF100 is not really important here.
Still I wanted to know what could be achieved. So I did some tests to determine the magnification, together with the working distance (from the lens) where this is achieved. I looked at the lens itself, the lens with 31 mm of extension tubes, the lens with the Raynox 250, and using both the extension tubes and the Raynox. Here are the results for the RF100.
At the left you see the numbers for the maximal magnification, achieved at the minimal focus distance. They show the width of the minimal area that can be photographed (in cm), the working distance where this is achieved (in cm) and the corresponding magnification factor. (This is all for an APS-C sensor.) At the right you get the maximal width possible, the corresponding distance and magnification factor. When just using the lens you can focus at infinity, so this is no useful information.
As can be seen the maximal magnification with just the macro lens is 2.25, as was to be expected from the specs. Adding extension tubes or the Raynox have a similar effect, but extension tubes allow you to stay further from your subject. Using both gives an amazing 5.14 magnification factor, but this is very hard to work with.
For the EF100 the numbers are, as expected, a bit lower. The Raynox though works surprisingly well.
Because of the hassle to use them, I think I will never use the extension tubes in the field. I might use the Raynox in certain rare situations where I need more magnification and can hold the camera against something solid. In a studio setting, I might use the combination to get maximal magnification, probably while using focus stacking.
Focus shift
What got me a bit worried about the RF100 were reports about focus shift. The Canon cameras (like most mirrorless cameras) use the widest aperture (F2.8 in this case) when focusing and only when you shoot the image the aperture is closed to what you set it to. Focus shift means that when the aperture becomes narrower (F number becomes higher) the plane of focus shifts a bit. This could mean that in the actual image, the point you were focusing on is no longer perfect in focus. This would be a serious issue as I often use F13 or F16 when shooting insects.
On the web, the opinions about this differ. Focus shift definitely happens in the RF100 (more than in the EF100) but does it effect your images? When narrowing the aperture also the depth of field increases. Some field test by others do not seem to show any problem. But to be sure I did my own tests. Here is one of the resulting images I produced:
It shows the RF100 lens at around 1x magnification, autofocusing on the 10 cm mark on a ruler. The ruler is at an angle of 45 degrees with the camera. From left to right the camera uses F2.8, F4, F5.6, F8. F11, and F16. ISO is 100 and shutter speed determined by the camera. No flash.
As you expect, the depth of field increases when the aperture gets narrower. I think that in all images the 10 cm mark is perfectly focused. However, if you look carefully you notice that the depth of field extends more to the back than to the front. I don’t know whether this is the result of focus shift. But my conclusion is that focus shift is not a serious problem for macro photography, even when using apertures like 11 or 16.
Just for completeness, here is a similar image for the EF100:
Conclusion
The RF100 is the better lens. It has more magnification, has better autofocus, seems slightly sharper, and is more modern. But are the improvements worth the large price difference? This is a difficult one. Buying the EF100 would be a considerable improvement over my current setup, and I would be happy with it. The slower autofocus would be the only thing that worries me a bit.
But you buy a lens for the coming 10 years. And I am afraid that at some moment I am going to want the improved sharpness and autofocus and the extra magnification. Also, lenses with RF mounts are the future, so the EF100 will lose its value pretty quickly, while the RF100 will be valuable for a long time to come.
So, even though it is a lot of money for a dedicated lens, I decided to buy the Canon RF 100mm F/2.8L Macro IS USM, as its full name is. Now I have to relearn a lot of stuff.
Next: Post Processing
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Mark Overmars is a dedicated insect photographer that loves to share and regularly publishes about his work and about photography in general. You can visit his website at www.insectphotography.org. Download his free insect photography book at www.insectphotography.org/book.
