5 Tips to Capture Fast Moving Subjects
The ability to focus on moving subjects takes time and practice. Whether you are trying to track a super sonic jet, an airborne athlete, a dog in full sprint, or a bird in flight, there are several settings that will improve your percentage of keepers. Of course, due to the demanding nature of high speed work, a greater number of OOF images (out of focus) is expected. Yet, with these techniques you'll have the ability to lock on and capture the peak of action more often than not.
1) Choose One Active AF Point (the center)
The center autofocus point is typically a cross type sensor which in simple terms means it's faster to achieve focus in comparison to the outer points. By using just one active AF point, you are simplifying the entire AF system. This actually works to your advantage over complex AF clusters which often fail to accurately grab the precise location you want sharpest. Since everything will be centered, you can crop later to create the desired composition.
While the outer points are helpful at creating different types of compositions, they reduce the effectiveness of autofocus on fast objects, and increase the chance for the AF to miss either by camera or user error.
2) Set the AF mode to AI Servo
If used properly, AI Servo can track moving subjects and continue to refocus even as they come towards you. The trick is to keep the single center AF point on your subject and keep your shutter pressed half way down. The ease of which this can be done is largely dependent on the speed and predictability of your subject's path.
With practice, you will get better at following the subject through the viewfinder. I like to keep both eyes open while doing this to benefit from my peripheral vision of the entire area.
3) Set the Camera to Continuous High
Rather than shooting one frame at a time, you can use this mode to fire multiple frames per second as the action heats up. Entry level DSLRs offer 3+ fps which is reasonably fast. Of course those models capable of 6+ will reduce the time between each frame, making it more likely that you'll catch the desired moment.
4) Raw or Jpeg?
Normally I shoot in RAW, but there is one problem when shooting high speed subjects; the buffer. If you are shooting in RAW, the buffer will fill quickly, and you could miss the action waiting for it to clear. In JPEG, this is not an issue as the file size isn't as large and can be written to the memory card faster. As such, it can be useful to switch out of RAW for these types of situations. If you opt for JPEG, just be sure to keep the quality to LARGE/FINE and you will enjoy a big buffer along with great image quality.
5) If the Photo is Too Dark
When shooting fast subjects, most camera users correctly choose a fast shutter such as 1/500 or 1/1000. These are good options for freezing motion, but they do not allow much light into the camera. As a result, it's often necessary to use a very wide aperture like f4, or f2.8, and a high ISO such as 800, 1600, or higher depending on the existing light.