Howdy friends! Raise your hand if this has ever happened to you. You take a photo and it appears sharp on the LCD screen. You get home and view it on your monitor only to realize the subject is blurry and the background (or foreground) is crystal clear.
Accurate focus is one of the most important factors for super sharp photos. To achieve accurate focus, you need to have the right focus settings in place.
When adjusting focus settings, it’s helpful to understand what focus points and focus modes are used for.
Focus points control WHERE focus is locked, while focus modes control HOW focus is acquired.
The D3100 comes with four different focus point options.
Single-point AF: You select the focus point.
Dynamic-area AF: You select the focus point and the D3100 will use surrounding focus points if the subject moves after locking focus (with AF-A or AF-C enabled).
Auto-area AF: The D3100 automatically chooses the best focus point.
3D-tracking: You select the focus point and the D3100 tracks the subject as it moves through the frame (with AF-A or AF-C enabled).
Most beginners leave Auto-area AF on all the time, allowing the D3100 to make all the decisions. However, if you want to make sure your intended subject is sharp, you may want to experiment with Single-point AF. I use Single-point AF whenever I shoot portraits to ensure the eyes are in focus. I use 3D-tracking and Auto-area for sports and fast moving subjects. Dynamic-area AF is good for shooting macro subjects outdoors and portraits of babies. In both instances, if the subject slightly moves from it’s original focus point dynamic-area AF will use the surrounding focus points to lock focus.
You can read more about focus points on page 58 of the D3100 manual.
The D3100 comes with four different focus mode options.
AF-A: The D3100 reads the scene and selects a focus mode automatically. If the subject is stationary, it locks focus. If the subject is moving, it enables continuous focus.
AF-S: Focus is locked when shutter button is pressed halfway. If the subject moves away from the initial focus point, the subject will no longer be in focus.
AF-C: The D3100 focuses continuously while shutter is pressed halfway.
MF: Focus is achieved manually by using the focusing ring on the lens.
Most beginners leave AF-A enabled, allowing the D3100 to automatically read the scene and select the appropriate focus mode. This mode works pretty well in some situations, but my advice is to use AF-S for stationary subjects and AF-C for moving subjects. AF-S is great for locking focus and re-composing the shot. AF-C is great for shooting sports, as the action is constantly moving in many different directions.
You can read more about focus modes on page 55 of the manual.
For more tips, advice and recommendations, check out the Nikon D3100 homepage. Happy shooting!