If you are taking a picture of a magnificent church, it’s a completely different thing than taking a picture of someone riding a bike in front of that same building.
You should always think about what it is you want to be in sharp focus in your image, and adjust your camera settings accordingly. In an article over at Digital Photography School this is what photographer James Brandon had to say on the subject.
One-Shot
This is probably the most commonly used method and is likely the ‘standard’ setting on your camera. When you press your shutter half way down (or use your AF-ON button instead) the camera sets focus one time and holds that focal distance until the picture is taken. If you’re shooting still life or a subject that simply isn’t moving much then this is a good method to use. You can even go into your settings and make the camera beep when focus is locked so you know it’s good. This setting is also a must when using flash in low light; for whatever reason (I really wish Canon would change this) the focusing grid on your external flash will only work in One Shot mode. Switching to Servo will disable the grid completely.
AI-Servo
Using AI-Servo was really a huge step forward for me . When I discovered it for the first time I was pretty blown away! AI-Servo tracks focus on moving subjects so as your subject moves closer or moves further away your camera constantly updates focus to keep the subject as sharp as possible. This means that a train could be headed straight towards you and you could set your center focus point over the nose of the train and your camera would keep the train in focus as it got close and closer. Eventually the train would be too close for your camera to focus though and at that time it’s best to get off the tracks (protip).
So Which One Is Best?
Well that really is the question isn’t it? Unfortunately there really isn’t a right answer. The better question is which one is better most of the time? And I will wager that the correct answer to that question is AI-Servo.
We found a great example video to show you how changing the focusing mode will make it so much easier to get sharp images of moving subjects.
GO TO THE NEXT PAGE FOR THE VIDEO
You can read the full article by James Brandon over at Digital Photography School
Source: Digital Photography School
Why are you applying this to if you shoot with a Nikon? It applies to all cameras the one shot and Al Servo.
The concept is the same Rick Kuperberg One Shot with Canon is AF-S with Nikon. AI Servo with Canon is AF-C with Nikon. Same principles apply. Would be nice if they both just called it the same thing.
This was a great tip. Especially in low light when getting focus can be hard. I’m officially a convert to back button focusing after just a few minutes of playing with it.
What is front focus vs back focus?
James Schultz, another article that may be helpful( especially using back button focus near end of article).
The only time my focus is on one shot is in my studio. In shooting belly dancing events in low light, road racing where cars are moving at speeds of 100 mph or more and roller derby where skaters are coming right at you, AI servo is the only way to go.
I do better with manual focus in those conditions
Seems to me back button auto focus gives me the best of both
to use the back button on Nikon anyway .. you have to be AF-C for it to work ……
The lady asked about back focus and front focus ….. check the video out about assigning the back button as your focus button rather than depressing shutter half way ……. when shooting something moving, keep holding back button down .. when it stops or your shooting static .. press back button down, let it up and shoot .. can let it up and recompose to as long as subject or you don’t move to change distance to the focused subject ……….
Fowling