The September meeting of the Calvert Photography Club was called to order by our President, T.O. Galloway, who was also our guest speaker today, along with club member, Rick Macquade. The topic was entitled “Focus on Focus” and we learned about the different focus modes that are available to us on our cameras as well as how to test and make adjustments to obtain the best focus possible.
When you set your camera lens to AF (auto focus), you have a choice between AF-S - Single Servo, or AF-C - Continuous Servo (for Nikon) or One-Shot and AI-Servo (on a Canon). AF-S or One-Shot mode is good for photographing subjects that don’t move, such as flowers or portraits etc. It locks the focus on the non-moving object that you want to photograph. AF-C or AI-Servo mode is good to use when photographing moving objects. When your camera is set to AF-C and you focus on a moving subject, such as a dog running towards you, the camera will keep re- focusing and the focus will stay on the animal as long as your shutter button is held half way down.
There are a number of focus points in your camera. Focus points are the little empty squares or dots that you see when you look through your viewfinder. Different cameras may have a different number of focus points. A greater number of focus points gives you more AF points to use when composing a shot and focusing on a particular area of an image. Also the camera AF system can use the different focus points for tracking a subject. In addition, there are also different types of AF points – vertical and cross-type sensors. T.O. explained that when shopping for a camera body it is important to pay attention to the total number of AF points along with the number of cross-type sensors. Cross-type sensors are more accurate than vertical sensors because they can detect contrast on both vertical and horizontal lines. The more cross-type sensors your camera has, the better and more accurate your camera’s autofocus will be.
Rick Macquade gave us a brief explanation on the use of back button focusing. Back button focusing is a way of separating the focus button from the shutter release button. This allows you to focus on your subject, then re-compose if needed, and then shoot as many images as you want without re-focusing. The back button is used for focusing. The shutter release is used only to release the shutter and expose the picture. By pressing and releasing the back button you lock the focus on your subject and if the subject doesn’t move, the camera stays focused on that subject (even if someone walks between you and the subject.) Conversely, if you press and hold the back button, the camera will continuously focus on a moving subject. So you can do either single focusing or continuous focusing depending on how you hold the button! Either press and release to lock focus, or continuously press for continuous focus.
Did you know that your camera may not be focusing as accurately as it should? And that some cameras have the capability of adjusting the focus point for the individual lens? For the remainder of our meeting time, T.O. And Rick helped a number of club members check their lens alignment using either a Lens Align product (around $100) or Dot-Tune (which is free – information can be found online!)
The October photo assignment is: Illustrate the concept of “Resist”.
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