Take some time to learn when manual focus is the better option, and how thinking about focus distance can lead to better images
THE VAST majority of photographers take autofocus for granted, but it wasn’t that long ago that manual focus was the only option. And it still has a huge part to play, particularly if you want to get the most accurate images possible.
For some subjects, manual focusing will be far too slow. However, it’s great for the type of shots that most enthusiasts take on a regular basis. You may even find the manual method faster and more accurate, as twisting the lens barrel can often be faster than changing the selected AF point. Not to mention that some lenses can suffer from front or back focus, causing images to be fractionally softer than they should be. In fact, one way to determine whether a lens suffers from front or back focus is to set a camera on a tripod, use autofocus and take pictures of a detailed subject.
For landscapes images, manual focus can be very beneficial, allowing the photographer to use the focus distance scale on the lens to set it to the hyperfocal distance point. This will maximise depth of field to make sure that both the subject and background are in focus, to infinity. For more on hyperfocal focusing see АР 13 July.
It can be difficult to use autofocus when photographing subjects in the sky, especially at night. For stars or fireworks, it is best to manually set the lens to infinity focus. How you do this will depend on your lens.
For instance, if your lens has a focus distance scale, manually focus at a set distance is easy, but not all lenses focus to infinity in the same way. Some have a ‘hard-stop’ infinity focus, which means that when you turn the focusing ring to its maximum focus distance it will stop at infinity. However, the focus nng on some lenses can turn slightly beyond infinity. This is where the common belief that you should always focus slightly back from infinity comes from. In fact, what you should be doing is turning the focusing ring until the focus indicator line is in the centre of the infinity symbol. This will guarantee you are focusing on infinity so you can concentrate on composing the image and finng the shutter at the correct time.
When you take macro images, manual focus should be your default. As the depth of field involved in macro imagery is so small, it can be difficult to get precise points in focus using AF Manual focus gives more control.
Manually focusing on your subject via the viewfinder can be a little difficult as the display may be a quite dark, especially if extension tubes or bellows have been used. If you a live view function, magnify the on-screen image as much as it will go. This will enable you to see tiny details much better.
PRESET MANUAL FOCUS
When taking documentary and street photos, it is often useful to preset the focus manually. By selecting a certain focus distance and aperture, the resulting depth of field will make it possible to capture the subject in focus. In this way, documentary photographers are able to use their cameras almost like a point-and-shoot, so the camera is ready the moment the shutter is fired, without autofocus getting in the way.
For example, when shooting with a 35mm lens on a camera with an APS-C-sized sensor, setting the lens aperture to f/11 and the focus distance to 4.5m will create a depth of field extending from 2.47m to 25.7m. This should be more than enough to for any documentary or street subject.
So, the next time you are out engaged in this type of photography, use this technique; and have more freedom to concentrate on composition and capturing the moment.