Photographing Insects: Focus
How to achieve the very important focus on the insect
It is crucial that the insects you photograph are in focus. And achieving focus is rather difficult when doing macro photography. In this article I give you my experiences with manual and automatic focus.
An extended version of this article has appeared in my free book My Journey into Insect Photography that you can download here.
Auto focus
My Canon R7 has great auto focus. Using spot focus I can indicated very precisely what to focus on. You need continuous focus (called servo on Canon cameras) because your camera is constantly moving slightly, changing the focus. However, I switched off subject tracking. If you have that on, the focus point can jump to places you don’t want. Similarly I do not use animal or eye tracking. I want to determine the focus point myself.
I normally use back-button auto focus, where you focus with a button on the back of the camera, rather than by half-pressing the shutter button. This is way more flexible. But for insects I switched back to using the shutter button. I realized that holding my thumb on the focus button while pressing the shutter button gave a less stable grip. And for macro you always want to focus the moment you press the shutter button anyway. Also, keeping the shutter button half-pressed is faster when I want to take the shot.
The auto focus on this camera is extremely fast, which is very important for macro shots. Most of the time I am happy with the result although sometimes the wrong part is in focus. So you always need to take multiple shots.
I encountered two issues with auto focus. The first is that you have to shift the focus point if you do not want to focus on the center of the image. This can be a bit hard. My solution is that I always first imagine how I want to photograph the insect. I change the focus point accordingly and only then approach the subject. As a result, taking the picture is considerably faster with less chance that the insect flies away. But it does not work when the insect moves around!
The second issue is that it is actually hard to keep the focus point on the correct position on the insect (like on the eyes). Very small movements of the camera move it to the wrong position and, hence, focusing wrongly. This probably requires more practice, but it can also be a reason to use manual focus.
Manual focus
Most articles and videos on macro photography recommend using manual focus. I think that this is less of an issue with modern cameras and their excellent and fast auto focus. But it still has its advantages. For one, many macro lenses do not support auto focus, so you must use manual focus.
There are two techniques for manual focus. The first is to fix the frame you want to photograph. Next you turn the focus ring on the lens to get the subject in focus. This is basically impossible when shooting insects handheld. You are always moving the camera slightly and, hence, you change the focus. But it is considered the preferred way to work when using a tripod. (More about tripods in the future.)
The second way is to fix the focus distance, often close to the minimum focus distance. Next you slowly move the camera forward and backward until the correct position is in focus. This is actually rather easy. Press the camera against your face (use the viewfinder), press your arms against your body, and slowly bend your upper body forward and backward. Don’t move your head or arms! Press the shutter button at the correct moment. I normally do that during the motion. So I do not stop the motion but simply continue it and press the button at the correct moment. Note that the higher the magnification factor, the harder it becomes to focus manually.
Manual focus support
Cameras have a couple of features to assist in manual focus.
Magnification. You can magnify the image you see with a factor of typically 5 or 10. So you only see the part you want to get in focus. Of course you must determine that part of the image in advance. For me this technique does not work. You must hold the camera extremely steady because all motions are magnified as well. I can image it work great with a tripod but, for me, not when shooting handheld.
Focus peaking. Focus peaking shows the pixels in the image where the camera determines that there is focus. These are typical places where there is an edge. Cameras use different techniques to determine those positions. Default the positions are colored red, but you can change the color when you have a red insect. These positions move when you move the camera forward and backward. When they are at the correct position, take the shot. I always have this on.
Focus guide. This is a Canon thing, and it works great. It shows the focus square, like when using auto focus, and when the object in the square is in focus, it turns green, again, like in auto focus. But what is even better, it shows three little arrows. The closer these arrows are to each other, the closer you are to focus and when they align focus is there. They even show whether you need to move closer to the subject or further away. I love this and use it all the time. While you move your body you see the arrows moving together. You predict when they will meet and then shoot. By clicking just before or just after the square turns green I can adapt the depth to focus on. Success almost guaranteed. (Well, you still need to take multiple images to be sure.)
One problem with focus guide it that it only works on a lens that has electronic connections to the body. Fully manual lenses, like the great Laowa macro lenses, do not have this, so focus guide does not work for them. This is actually a strong argument for me not to get such a lens!
Focus depth
Focus depth, or depth of field as it is often called, is the distance range that is in focus. (The precise definition of this is actually very complex, dealing with something called the circle of confusion.) This depends, among others, on the magnification and on the aperture you use. A narrow aperture (high F number) gives you a larger depth of field, getting more of your subject in focus.
A useful technique here is to make sure the whole insect lies in the focus plane, that is, the plane where there is focus. This normally means photographing the insect from the side or top and making sure the back of the insect is at the same distance from the lens as the front.
Still, it is often impossible to get the whole insect in focus, in particular when you photograph it from the front. And that gives the nicest images. But this does not need to be an issue. Having only part of the insect in focus will actually guide the viewer to the important spot, as the following picture shows. I will talk more about depth of field and other theoretical aspects in the next article.
Next: Some Theory
Previous: Using a Flash
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.
