One area that I am increasingly focussing on (excuse the pun!) in my training courses is how to maximise the power of your camera's focussing system. As with ND filters (my blog topic last week), I find that camera focus modes is another area that can be confusing. Get it wrong and you can end up with blurred photos, but get it right and you may discover that your camera has hidden focussing powers that you didn't even know about!
The main focus modes
As long as you have a Bridge, DSLR or mirrorless camera (not just a camera phone or compact 'point and shoot' camera) then you are likely to have a number of focus modes available to you, each of which are suitable for different situations. How you access them will depend very much on your camera make and model (time to check the manual!) but the main focus modes are: AF-S, AF-C, AF-A and M (Manual). Although Manual is denoted by M across different camera makes, the other modes have different names across different manufacturers, so an explainer can be found in the table below.
These four focus modes, what they are and when you use them, are explained in the remainder of this article.
Single shot (AF-S)
This is the simplest focus mode, and is the one that I use most of the time for landscape photography. It effectively means that the camera acquires focus as you depress the shutter button halfway (when you should hear that satisfying beep!), and then locks that focus as you take a single shot by depressing the shutter all the way. This is most appropriate to landscape photography, as there is normally nothing moving in the photo, and so once you have achieved the appropriate focus, there is no need to change it before taking the shot.
Continuous (AF-C)
If you often take photos of wildlife, sports, air shows or similar, where there is an object moving in your frame, then this is the focus mode for you! In this mode, the camera acquires focus as you depress the shutter button halfway, but unlike in AF-S mode, if something moves before you take the shot, your focus system will ATTEMPT TO TRACK IT. This means that if you are taking a photo of a bird, and it starts to fly away from you, or across the frame, the camera autofocus system will do it's best to follow the bird and keep it in focus. This is obviously most critical if you are using a shallow depth of field, where only a shallow part of the image is in focus, and if you have something like a jet plane, using AF-C is likely to be your only chance to ensure you nail the focus. How well your camera does this depends very much on your camera model and its capabilities, but many modern cameras can do this very effectively.
Automatic (AF-A)
The automatic mode is designed to take the decision of AF-C or AF-S out of your hands. Essentially, the camera is meant to decide whether it detects anything moving, and then use AF-C or AF-S as appropriate. In reality, in most cameras this mode can be rather temperamental, and I usually do NOT recommend that you use this mode.
When to use Manual focus (M)
In landscape photography, my camera is generally set to AF-C, however there are some situations where Manual focus becomes a necessity. In Manual focus mode, your camera's autofocus is turned off completely, and focus can only be achieved by rotating the focus ring on your lens until the object that you want in focus, is in focus. This takes some time, and so this mode is NOT applicable for moving subjects. There are a number of situations where Manual focus is the way to go. These include:
Low light scenes. In low light situations, it's possible that your camera's autofocus system won't function correctly. As you half press the shutter, the lens may shudder slightly as it 'hunts for focus' and you don't get a satisfying beep to let you know that focus has been achieved. It's quite likely that if you've tried taking photos at dusk, or tried your hand at astrophotography, this is exactly what has happened. In these situations, Manual focus is your friend.
Low contrast scenes. Camera autofocus systems rely on contrast in a scene to work effectively, so if you have a low contrast scene (e.g. a uniform field of snow) then your autofocus may not work, and you'll need to embrace Manual focus.
Macro photography. In macro photography, where you are taking photos very close to your subject, you effectively have an extremely narrow depth of field (the plane of focus is very narrow). For example, if you're taking a photo of a fly, their eyes might be in focus, but the rest of them is out of focus. In these situations, it's really important to make sure that exactly the right part of your scene is in focus, and for this fine control, Manual focus is the best way ahead.
Panoramas. When photographing a panorama, you need to take a series of photos and stitch them together. Clearly for a good result, it's important that all the frames have the same plane of focus, and so it's good practice to use Manual focus to ensure that the focus doesn't change between frames.
How to use Manual focus
In simple terms, to manually focus, you simply turn your lens focus ring until the part of the frame that you want in focus, is in focus. However, many cameras have a number of features which can help you to do this well:
Auto zoom. Some cameras have a setting whereby as soon as you start turning your lens zoom ring, your on screen display zooms into a small proportion of the scene. You may be able to control the portion of the scene that you are viewing. This is a very effective way to see when critical parts of the scene (usually the main subject) come into focus. Check your camera manual to see if you have this feature and how to enable it.
Focus peaking. Some mirrorless cameras have a focus peaking function. When this is enabled. portions of the image that are in focus, are highlighted by being outlined in a bright colour (usually red or yellow). This is an additional way of knowing when key parts of your frame are in focus. Check your camera manual to see if you have this feature and how to enable it.
Focus modes are only part of the focussing picture
As well as focus modes, there is another aspect of focussing to understand how to focus effectively; this is how to control where you focus by using different focus points or areas. Watch this space for a feature on this in next week's blog post!
