Autofocus Modes Explained
By Geoff Harris •
The process of becoming a more skilled and creative photographer involves moving away from the 'out of the box' automatic settings on your camera, and taking control of it yourself. While many enthusiast photographers understand that they need to get beyond auto-everything or Program shooting modes to take more creative shots, you may not realise you also need to take control of automatic focussing.
This sounds counterintuitive; surely the whole point of autofocus (one of the greatest breakthroughs in camera technology of the last 50 years) is that it's, er, automatic? True, but even fairly basic compacts now give you a range of autofocus (AF) options to suit different focussing needs and situations. This is the point – focussing on a static rock in a landscape is a very different exercise from focussing on a racing car or bird.
Digital SLRs now offer a bewildering range of AF options and some are much more useful than others. To help with autofocus, here's a quick guide to what mode to use in different situations. NB: you don't adjust AF modes in exactly the same way on every camera, so while the principle is the same, you'll need to consult your manual for specific guidance.
1) Still objects/portraits
If you are shooting a static subject, you will often get the sharpest results if you select single point or one shot AF mode. When you do this, you will notice a series of AF points, which you can usually move via a button or joystick device on your camera. The central point is the most sensitive, so try placing this over the area that absolutely needs to be in focus – the eyes on a portrait, for instance.
You can then half press the shutter button to lock this focus, and recompose for a better composition (so long as your subject stays still and the distance between you and the subject stays the same). Or, select the nearest AF point to where you need to focus and move it as necessary.
2) Moving subjects
With moving subjects it can be trickier, but rather than just relying on the default AF settings, we recommend choosing continuous AF, also known as Servo AF on Canon cameras. It's still important to keep the active AF point close to where you must stay sharp – the eyes or beak on a flying bird, for example, or the helmet of a racing car driver. Continuous AF should also be used with slower moving subjects, such as a bride walking down the aisle, again keeping the AF point over the 'hot spot.'
3) Group shots
So long as your group is not moving too much you should also use single point AF and focus on the centre of the group, but you can also try Face Detection AF (if available) as you can be sure the camera is focusing on actual faces. It can get confused though, so Face Detection AF tends to work better with smaller gatherings.
//image needed of group//
If your shots are still not sharp after taking control of your AF, there are probably other factors at work. It's imperative that you use a tripod if you are shooting in low light, or at a very narrow aperture (higher f number) or slow shutter speed (less than 1/15th sec). Aperture choice is also crucial.
The sharpest results are usually found around two to three stops from the widest setting – f/8 or f/11 for instance. Try this if you are having trouble with group shots. Finally, if you are having trouble keeping your landscapes sharp, try using a shorter lens focal length, then set a wider aperture (e.g. f/11) and focus around a third into the scene.
Since landscapes don't move much you can also get great results by switching to Manual focus on your lens, then zoom in to where you want to focus with Live View on the camera's rear screen (not zooming in with the lens!). Once you can see in Live View that you have got correct focus, you are good to go. Again, a tripod is essential at slow shutter speeds or in low light.
If you would like to learn more about child photography with David Handley or Bird Photography with David Tipling why not consider taking the following 4 week online classed
http://www.my-photo-school.com/course/photographing-children/
http://www.my-photo-school.com/course/bird-photography/
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