This one’s an easy, cool trick.
Using the focus trap technique you can set a ‘trap’ for your subjects at a particular spot in your scene and just as your subject comes into focus, the camera takes the shot.
Sounds cool, isn’t it?
In theory, this technique should give you perfectly focused images. Every single time.
Oh no, you don’t need any fancy gear for any of this. Any DSLR or Mirrorless camera will do. Just the camera and the lens.
The most important bit of information you need to know to make this focus trick work is the spot where the action is going to happen.
That is right, you need to know beforehand where a certain event of which you want an image of, is going to happen.
That is all. You can deal with the rest yourself.
The Process Overview
The idea is pretty simple and straightforward.
Once we know where the action is about to occur, we prefocus on that area and then instruct our camera to take an image as soon as it finds something in focus.
Let’s take an example where you can use this in real life.
Say, you are at a football match (which my friends in the United States call a soccer match). You are sitting at the sidelines and want a good image when a goal is scored.
The most important thing you require to employ this technique of prefocusing as I said earlier, is the information about the position of the action in the frame.
In this case, you know that already. It’s the goal post.
Goals cannot happen at the centrefield.
So you select a good spot for yourself from where if you take the image it will have good composition and lighting.
Now, all that is left to do is to prefocus in the general area where the players are sure to be at when the goal is scored and wait.
When the players actually come and hit the place where you set the focus trap for them, the camera shutter fires, and the image is captured. Easy-peasy!
There is nothing fancy about the way focus traps are set and executed.
The entire premise is based on a function called AutoFocus Release Priority.
Don’t get confused by the long, colorful name. All it does is determine whether or not to take the shot when you press the shutter button?
Not take the shot when I press the shutter button?
Let me tell you the whole story and then you will surely get why this might happen.
Generally, the AF Release Priority has two sub-settings.
When you select the first option, ‘Release’, the camera just takes the shot whenever the shutter button is fully pressed.
This seems how all cameras work, right?
Well just hear out how the next option works.
When the ‘Focus’ option is engaged, each time the shutter button is pressed down, the camera checks if it has a solid focus lock. If and only if the camera feels that it has some of the elements of the scene in focus will it take the shot.
Else, it will simply refuse.
No points for guessing that we use the latter Autofocus option for the focus trap to work.
Just to have a little more control over the area where we want the trap to be set and the exact moment when the shutter is triggered, we need to adjust two more settings. We need to change the Autofocus mode to One-Shot or AF-S and the Autofocus Points to Single/One.
These two functions together ensure two very important aspects required for the Focus trap to work properly:
- We only focus once.
- Only one point of the entire frame is evaluated if it is indeed in focus or not.
Let’s run a quick recap then.
For the settings, we need to choose AF-S or One-Shot as the AF mode so that the camera focuses only once.
For the Focus area, we choose Single Point so that only one point is monitored for focus checks by our camera.
Last, we need to choose Focus as the AF Release Priority to tell the camera to ONLY take the shot when it finds a good focus lock.
The first two settings should have the same names that I used here. Autofocus Release Priority may have a slightly different name in your particular make and model, just perform a quick Google search and it should find you the settings name you need.
Remember the function you need to change and I am sure you will find it on your camera.
Apart from the scenarios that I discussed above, you can also use the Focus trap technique to shoot tack sharp images in situations when it might be difficult for your camera to actually acquire focus.
Situations when this might happen is a cause for concern.
Imagine a dark, dimly lit set in which the light keeps on changing color and intensity every second. This is the perfect nightmare.
For the camera to acquire focus, it needs light. More light is nearly always better.
It is no wonder then that the autofocusing system is going to struggle pretty hard in low-light situations.
To use the Focus trap in a situation like this, first and foremost find the place where the action is going to happen. As always!
Let’s say there is a mic stand. So you know for sure that whatever happens, the singer has to come up to the mic to sing. You have the position then.
Now just focus on the mic or a little behind it when you get the chance and when the lighting gets a little better.
Once you acquire focus, keep pointing the camera towards the mic and the shutter button pressed fully down. Don’t worry the camera will not take any images, it would wait for something to be in focus.
As soon as the singer walks up to the mic, the camera finds him within the ‘trap’ and it fires the shutter. It need not focus at all since you already did that.
This is much quicker and reliable in situations like this.
Just make sure that you do not move much from the position you prefocused the camera from.
Back Button Integration
If you already use Back Button Focusing (you should definitely try it out if you haven’t already), the only setting you need to change is the AF Release Priority. Set it to ‘Focus’ and you are ready to set your first trap.
That is it, guys. That is all you need to know how to set a trap for your subjects. I know it sounds sinister at first but you are using it to create great images, so it’s cool.
Let me know how it works out for you, and if it indeed gives you the results you want.
Keep shooting beautiful.