Recently I was posed a question by Andy, who asked: When shooting dynamic subjects, what’s the best auto focus mode and what is “dynamic AF point selection” used for?
First, let me start by saying if you have your cameras set to “auto area” focus, referring to your focal cursor points, you probably want to set it to “single point.” Auto area is the camera’s evaluation of what it thinks you’re trying to focus on (normally the closest subject to the camera) and can give very inconsistent results. It displays this by different flashing points every time you try to focus. For precise auto focus, use the single focal cursor point, and you then have the ability to move that point anywhere in the viewfinder. Refer to Image 1 to see how I used the single focal cursor to focus on the second flower from the right, on the bottom. This technique negates the need to recompose, unlike having the cursor in the middle.
Revisiting our first question now, when working with fast-action subjects it’s best to use continuous mode, which allows the camera to track the subject, and also have the focal cursor area set to “dynamic” for Nikon, or (AF point expansion) for Canon. What this looks like in the viewfinder when focusing is still one high light cursor point; however, in this mode you have surrounding points acting as support points (even though they don’t show up in the view finder). While tracking a subject, if your focal cursor point misses your target even briefly, the supporting points will maintain focus.
In Image 2, I was ready and waiting for the professional stand-up paddle boarder as he approached very quickly. Having the camera set in continuous AF, and the single focal cursor set to the top left corner of my camera’s viewfinder (while utilizing dynamic AF point mode), I was able to maintain the focus on the subject’s upper body. Even if I had temporarily missed my focus, the “support focal cursors” in dynamic AF point mode would have maintained sharp, predictive focus. This technique works very well for things like birds in flight, sporting events or anything with unpredictable movements.
The second question I received, and have on multiple occasions, is: How do I achieve the sun’s starburst while still getting a properly exposed image? This technique is best achieved in manual mode. To illustrate, let’s look at Image 3. Since I live in an arid area of the country, I work with the sun a lot! Instead of fighting it, I’ve learned to use it to create more impactful images. In this case I used an aperture setting of f11 (to achieve the star effect with the sun.) A higher numbered aperture achieves a better star quality (try f16 or f18 for city lights).
I then pointed my camera up to the sky to the right of the sun. Make sure you’re close to the sun, but not including it when setting your exposure. Now, set your shutter speed to what the camera’s metering system is telling you (meaning the line graph on the bottom of your viewfinder is showing “0″). Now you can recompose and take your first image. Next, check your histogram. You may need to overexpose more (or slow your shutter speed down) to achieve an optimal histogram that has your subject properly exposed. The only blowouts in your image should be the sun!
To read more of Kelly Funk’s columns and other great how-to articles please pick up the Summer/Fall 2014 issue of OPC today, or subscribe!