Cool Camera Tricks:
Two Button Focusing
This week in Cool Camera Tricks, I want to talk about a novel trick for managing auto-focus (A/F) in situations where the environment demands both tracking and static auto-focus, nearly interchangeably and quickly. For lack of a better word, I’m calling this 2-button focusing.
In it’s normal default configuration, and how it’s normally used, almost all cameras start their AF and auto-exposure metering (A/E) when the shutter release is half pressed. This is often just fine in most situations as there’s no real need to flip/flop between a tracking AF and a static AF, or at least do so quickly. Often though in wildlife photography, especially when shooting at a preserve like Wakodahatchee wetlands or Green Cay wetlands in Palm Beach county, you have a verity of shots switching rapidly between flight shots demanding continuous tracking AF and static shots of a bird on a perch or branch. In this case it can be difficult to remember to, or have enough time to, switch between the tracking AF and single shot AF.
The solution is to decouple the AF control from the metering so that you can still have the shutter release half pressed to take a shot, but have the AF controlled separately.
Before I get into the details of setting this up, here’s roughly how it works in practice. With the AF controlled by the AF-On button on the rear of the camera, an the focus mode set to continuous tracking, a flight shot can be done simply by holding the focus button with your thumb and the shutter release with your index finger as you would normally do. The AF system will track whatever is targeted, as long as the focus button is pressed. Then say you turn around and there’s a bird perched on the plant right behind you, normally if you continued to shoot with the tracking AF enabled, you’d have keep the center focus point on the bird to keep the camera from shifting the focus. Obviously that limits your compositional probabilities. The normal solution to the situation would be to set the AF mode to single shot, then focus and recompose. But not with two button focusing; with TBF you simply place your active focus point over the bird as you would in single shot AF, and press the AF button. When the focus correct, you simply release the focus button and shoot like you would if you were shooting in single shot or even if the camera was manual focus.
What’s needed for this to work? Obviously you need the ability to program one of the rear buttons to act as the AF-On button and the ability to remap it to control the AF.
