Getting focus is in theory very simple. You point the camera, you wait for the focus confirmation, and you take the picture. But as we all know things don’t always work that way.
Achieving focus is somewhat arbitrary in the sense that it is dependent on many factors, starting with depth of field.
Depth of field can be tricky to understand. We talk about depth of field with the implication that the point of focus has depth when the point of focus is literally at a point, it has no depth. The reason we say, “depth of field” is simply a short hand way of saying “the area of the light cone that appears to be in focus”. Appears is the keyword here because “appears” to be in focus can mean different things depending on the camera sensor, the print resolution, the print size, and the print viewing distance.
For instance, if you view photos on a phone the “depth of field” is drastically larger than if you view the photo as a 16×20 print. This is simply a matter of detail being hidden the smaller an image is. You can test this in your favorite editing application. Open a picture that is slightly out of focus and zoom out until it appears sharp. Now zoom in to your image and blow it up until it appears to fit 16×20, does it still look sharp? If not, then it obviously isn’t good enough to be printed at that size.
All this means “depth of field” is generally relative to the size of the print. So, when determining if something is in focus or not think about the media you are targeting. For instance, if you’re targeting Instagram, you can get away with an out of focus image that you wouldn’t get away with in a typical print.
To understand more about depth of field check out my quick tip: How to control depth of field.
All this is well and good but what is good focus in practice? Generally, the subject of your photo should be in focus, no matter where it is in frame. If you’re really close to your subject and have narrow depth of field you should try to get a prominent feature of the subject in focus, typically with people this would be the eyes. If you don’t focus on the eyes your photo might be in danger of being called out of focus.
Be still when focusing
To achieve focus you need to be careful, especially with a wide aperture lens. Remember the point of focus is literally a point, if you move a millimeter that point moves a millimeter out of focus on your subject.
If you’re using ONE SHOT AF what you should do is frame your shot with your focus points on the subject, then hold still, then focus, then immediately take the picture after the camera achieves focus.
For a lot of you the true progression of events is probably more like, change framing to get focus points on face of subject, get focus confirmation, carefully reframe the subject, then take a picture.
If you’re doing anything after you get focus confirmation, even if its just waiting too long, that is probably why you’re messing up your focus on your shots.
Frame your shot wider
If you’re having trouble framing your shot, you need to back up or zoom out. A lot of photographers shoot this way, they shoot wide then crop later. It’s a perfectly valid way of working. Not only will you find it easier to frame your shot this way, but you also increase the depth of field by increasing the field of view.
Use a different focus mode
Another option for your focus is to use AI SERVO instead of ONE SHOT. If you have a Canon 80D or better, you have access to tracking AF that you can use to set your initial AF point, start focusing with that point on a person’s face, and then the camera will track the face across all available AF points. This is a very useful way to shoot if you don’t want to worry about adjusting your AF points manually. Below are two shots where I used the tracking AF of AI SERVO on my Canon 6D II to track my subject from one side of the frame to the other side when they changed their pose. With these models on the runway I only have a second or two to get my shots, so choosing the right focus mode is key.
Have any other tips for achieving perfect focus? Let us know about it in the comments below!