Not all autofocus systems are created equal.
Over the next few weeks we’ll be covering one of the most popular subjects with our readers “How To Take Sharper Photos” One big chunk of this learning will be centered around autofocus and how to master it.
This article is dedicated to autofocus points and how to use them. When looking through the viewfinder of your camera you’ll see a series of dots arranged in a pattern. These are your AF or focus points.
Today’s modern digital cameras have incredibly precise autofocusing systems
However, they vary in degrees of accuracy from system to system and are definitely not 100% foolproof. Whenever I sort through a batch of images there are always images that don’t make the cut because they have a soft focus.
For example if you’re shooting with a Canon 6D which is on the lowest end of the Canon full frame DSLR’s you have a total of 11 autofocus points with just one cross-type focusing point in the very center.
One the flip side if you’re shooting with a Canon 5D Mark III you have one of the most advanced autofocusing systems that Canon offers. There are 61 autofocus points and as many as 41 cross-type autofocus points depending on the type of lens you’re using with the camera.
Shooting with more autofocus points is not always better
If you are using your autofocusing in automatic mode all of the focus points are selected. Initially that might sound like a good thing but, in a situation where you’re shooting a scene with a large depth you run the risk of objects in front of or behind your subject being in focus while your subject itself is out of focus.
It’s only when you start selecting groups of autofocus points or individual autofocus points that you can really leverage the power of these advanced focusing systems.
The buttons and/or wheel that you use to select individual or group autofocus points can vary from camera to camera so you’ll need to consult your manual. I rarely use focusing groups and almost always use a single autofocus point.
I generally use a cross-type focusing point
There are what’s known as vertical and cross-type AF points. When focusing on a scene the focusing point is looking for contrast. A vertical sensor can only detect contrast on one dimension. Either horizontal or vertical depending on the orientation of that sensor.
A cross-type sensor can detect contrast of both dimensions horizontal and vertical. So as you can see the corss-type sensor has the potential for being far more accurate depending upon the type of scene you’re shooting
This is a basic overview of autofocusing points. We can get far more technical in these explanations. I don’t believe that diving that far down the rabbit hole will make as big a difference in your photography as a mastery of the following basics based upon the information here.
I recommend learning about your camera’s autofocusing system. How many sensors does it have? What types of sensors are they? Cross-type or vertical? Where are they positioned and, how do you select them individually and/or by groups?
Once you’ve answered these basic questions get out and practice, practice, practice. Learn to select the right autofocus points for your shooting situation. If you do I have no doubt your photography will improve greatly.