In the Desktop Macro Photography video, I did not go fully into the camera auto-focus modes and what the general recommendations would be for different scenarios. This is what we will discuss here.
I have only Nikon bodies, so, I can only talk in those terms. Other brands would have equivalents of the modes that I will talk about here.
For this brief session, I would strongly recommend that you put on the macro lens on your camera body and pause the video, where needed, and try out the settings that we discuss here.
Depending on the camera body, the number of focus points and groups would differ, but, we are generally not really concerned with that since we will generally use only a single focus point for the Af-Area (S).
The AF-Mode, unlike for most other purposes, will also be single shot or AF-S instead of the more commonly used AF-C.
As I explained in an earlier video, Nikon users would have to go into the custom settings and make sure that AF-S is set to focus, which is the default. As a side note, I use focus priority for AF-C as well.
I am assuming that your camera is already set up for back button focus. This is a requirement and not optional in this case.
So, for the Nikons, you would use AF-S/S for macros and make sure the AF-S is set to focus priority.
What this setup does is that the camera will not release the shutter unless it has focus on something. You can keep the shutter button pressed and nothing will happen till there is some object that the camera thinks it has the focus locked on to.
Now for the exercise to check this out…
- Rotate the focus ring on your lens to the minimum distance, i.e. at 1:1. For most macro lenses, the MWD would be around 10 cm, but, do check your lens’ specs for that.
- It does not matter what the camera settings for the exposure are for this test. You can set the camera to full auto mode as well. We are not concerned with the exposure here.
- Place an object, I will use the same sanitiser bottle we used in the earlier video, on your desktop and look at the object through the viewfinder of the camera while keeping the shutter release button pressed. The shutter will only release once you have the camera close enough to the object for the camera to acquire a focus lock on the object. This will not work if you do not have back button focus set up.
This is also referred to as a “focus trap” and can be used in other scenarios as well.
So…How does this experiment help?
Given the razor sharp DoF when shooting macros, the point of focus becomes critical.
For example, this is a snapshot from one of the many DoF calculators available online. Although lenses in real life are far more complex than this simple computation, but, this does give you an idea of the DoF when fully stopped down on this Tamron 90mm macro lens.
This is also the only way you can be sure that at least the camera “thinks” it has the subject in focus. This will almost always be correct unless your lens is front or back focussing. I will explain how to correct this issue in a later video.
Now, one might wonder if this is it!
The ultimate settings for macro photography…
Not really, this is just the ideal scenario which may or may not happen in the wild or even your own desktop unless you have sufficient light for the camera to detect and lock focus. This is just the only way to go about getting the smaller subjects where you want to make sure you are shooting at a full 1:1 magnification. Using AF would generally lock at any distance over the MFD and you might not get 1:1.
For subjects larger than the sensor size or if you are looking for more of a composition close shot, the AF works fine most of the time in all such cases. In fact, for larger subjects, you can even switch back to AF-C/Any Focus-Area mode.
Okay, so, where would this fail or not be desirable?
One, of course, as we already discussed, for larger subjects, it does not matter what modes you use. The prime macro lens will give you a much better IQ than a zoom in all these cases.
The second is in low light scenarios. I don’t mean low light as in late evening or similar. What I mean is when shooting wildlife in the open, the subject might be in a location where the light and/or the contrast of the subject will not allow the camera to figure out if it has acquired focus. Even though you might see a sharp image in your viewfinder, the camera will refuse to release the shutter. In such cases, just change to a group focus or auto and shoot before the subject vanishes.
The third is if you get lucky and get a subject in the wild that is stationary for a few seconds even after the first shot with the flash. This is a perfect opportunity to try and get multiple shots and stack them later. This is generally referred to as focus stacking and we will see how this is done in a later video.
Of course, there are specific instances as well. For example, if you are shooting some object in a glass and want to focus on a specific point.
I hope this clarifies the focus mode and areas when shooting macros.