Trap Focus for Nikon

[kinetic]

Trap Focus for Nikon Users
Here's a helpful tip for shooting fast-moving objects.

Camera settings:
Custom menu (pencil):
Auto focus set to AF-S
AF area mode set to single
AE-L/AF-L set to AF ON

Compose your shot and set the focus by aiming the centre focus icon at a definite target
at the precise distance you want, for example, a branch where a bird is about to land,
or on second base where the baseball player's foot will land. Press the "AE-L/AF-L" button near the viewfinder.
This will focus the lens, then let go of AE-L/AF-L button. Turn away, press and hold the shutter button
all the way down now turn the camera back to the pre-focused point and wait, when the subject
gets in the sweet spot the camera will take the shot.

This method is said to work faster than human reflexes.

[eyerkish]

Great tip, Mark. Thanks for sharing. I think I'll give it a try.

[jerryph]

Different cameras will be a bit different, and for a Nikon D700, you can mimic "Trap Focus" with the following settings:

1. Set custom setting #A5 to AF-ON ONLY

2. Set the focus mode to SINGLE SERVO

3. Set Auto focus area mode to SINGLE POINT (9 point, 21 point, 51 point or 51 point 3-D will all work)

4. If your lens has an A/M switch, make sure it is set to A for autofocus mode.

5. Pre-focus the lens for a particular distance. Don't forget that a more convenient way to use this trick is to pre-focus using not the shutter button, but the FOCUS button on the back of the camera can be used. I find this easier and more effective.

6. Press and hold the shutter release ALL the way down, the camera shoots only when the selected focus bracket is in focus.

"Trap Focus" is only effective if you know exactly where your moving object will stop and you yourself do not move or change position from (ie: the examples of a baseball plate or a branch where you expect a bird to land are very good, and having a deeper DOF is also a strong consideration when very close to the subject).

Another place where "Trap Focus" comes in handy, and not many people know or use it with, is with hand held macro shots. If you are using the trap focus method, you focus on a particular area, are ready to take a shot, breathe perhaps a little, the scene goes ever so slightly out of focus, the camera will refuse to take the shot until you adjust position, camera focuses and the shot is sharp. In this case, "Trap Focus" saved you from taking a blurry picture.

However, it is not very good for use where we want to capture a moving object and we do not know the exact location where it will stop, or in cases where an object moves from sensors on one side of the screen to the other.

In these cases, continual focus or continuous servo, as Nikon calls it (in conjunction with a Dynamic AF setting and Single Point focus area), gives me far more keepers than using "Trap Focus" (ie: bride and groom are moving down the isle and you are moving to keep up with them), as I choose the STARTING focus point and as they move (I may want to recompose the shot on the fly), the focus remains on the subject that I initially set the starting focus point on. It does this because the lens is continually trying to focus as long as I have the shutter pressed instead of waiting on that one point/distance where focus is achieved and the shutter trips to take the shot, and if they move to another sensor, focus tracking is in place and focus is continually modified and locked.

Trap Focus has caused me to lose or miss the moment many times in the past before I learned to understand the D700 focus and exposure system and how it works in detail and when to use each of the proper settings to best effect.

Knowing your camera and it's capabilities intimately permits you to get the most out of your camera under the greatest variety of situations and conditions. :)

[eyerkish]

Sound advice, Jerry. Thanks for sharing your knowledge and experience.

[kinetic]

Hi Eddie and Jerry, I think Jerry, that you have given good examples of where trap focus can and cant be used,
or maybe not cant be used, but less desirable in a given scenario. More good advice comes in your comments with
regards to understanding the tools to be used to achieve the job in hand. It goes without saying, that the more you
understand how to use the tools the better the job will turn out, that is of course if all the other ingredients that go
into making up the subject of photography are applied, (and that’s for another posting).

One scenario I am keen to give trap focus a go with is in that of “bee flight”. I got reasonable photos of bees in flight
with a bit of patients and a bit more luck. I want to remove some of the luck part and shoot with more intent and with
a method that will yield better results, is that method trap focus, well I suppose time will tell.
Mark

[jerryph]

...is that method trap focus, well I suppose time will tell.

It sure can be, Mark, as long as you know where it will land (bees going from flower to flower are fairly predictable, and if you get a little lucky, could nail the sharpest bee shot ever. :)