• Ed Dozier

Focus-Trap Shooting on the D500 and D850

Have you ever heard of focus-trap shooting? That’s where you set up your camera to wait until a subject moves into a pre-set zone of sharp focus. As the subject enters that zone, the camera automatically starts shooting. It stops shooting after the subject leaves the focus zone. If the subject re-enters the zone, the camera will start shooting once again.



Humming bird fly-by: caught in a focus trap


Focus-trap is useful for things like the finish line of races, where the photographer isn’t allowed to be there. He sets up his camera to automatically shoot the end of the race with his camera unattended. This feature is also used beside a trail where shy or dangerous wild animals will wander by, and you have your camera in a secured box with a hole in it for the lens to see through. It’s also great for shy bugs moving onto a pre-focused spot over a flower or waiting for birds to land on a perch.


It’s not very straight-forward how you can do focus-trap with the Nikon D500 or D850, but it’s possible to do.




High speed hummer: not easy to react to.


For the shot above, I set up a focus position in mid-air where I knew that a humming bird would fly past on its way to eat. It’s almost impossible to shoot a humming bird up close if it’s not hovering or perching. With a focus trap, the camera could easily do what I find exceedingly difficult to do: get a shot in flight from just a few feet away.


How to set up the camera


Pre-focus your lens to the distance where you want your camera to trigger shooting.


Set your shutter release to AF-C mode, and make sure you’re in auto-focus mode. Set Ch for high-speed continuous shooting to get lots of shots while the subject is in focus. This won’t work in manual-focus mode.


You might want to set your focus-point selection to ‘single’, if you want a very selective focus zone, but this isn’t mandatory.




Autofocus menu





AF-C shooting priority configuration




Focus priority with AF-C: only shoot an in-focus subject




AF activation menu




Select AF-ON only. Don’t allow combined shutter and focus




Disable the Out-of-focus shutter release



Go to the ‘Custom Settings’ (pencil menu) “a1AF-C priority selection.


Select “Focus” (you may want to switch back to something like “Focus + release” after you’re done with focus-trap shooting).


Go to the “a8AF Activation | AF-ON only | Out-of-focus release | Disable


Now, point your camera in the direction of the zone where you want the subject to trigger shooting after it comes into focus. You probably want to set your camera on a tripod at this point, unless you plan on holding the camera yourself.


Don’t touch the AF-On button! The trick here is that your camera can’t (auto)focus on its own, because this button doesn’t ever get pressed.




Unattended operation: wired remote with shutter-hold feature




Hold down the shutter, or use a wired remote that has a locking feature on its shutter release function to keep the shutter release active. The shutter is “held down” until you unlock it.


When the subject moves into the correct-focus region, the camera will start shooting until the subject leaves the zone of focus. If the subject re-enters the zone of focus, the camera will start shooting once again.


Make sure that you test your setup by waving your hand in the desired focus zone and verify the camera starts shooting. You’d hate to waste an hour waiting for that animal to arrive, only to discover later that you had overlooked something in the setup that caused to camera to ignore taking the shot.


Remember to go back to the “a1” menu when you’re done, and restore the original setting you had (such as “Focus + release”). If you don’t remember to restore the old setting, you’ll get burned later when you try shooting and your camera behaves strangely.


Many of the flying bird close-up shots require you switch to “M” and set a really high shutter (1/4000 and faster) with Auto-ISO and a stopped-down aperture to get some depth of focus. The Auto-ISO options on something like Aperture-priority mode just won’t go fast enough for the focal length.


This mode of shooting causes fairly high battery drain, so be aware of that fact. Charge up your battery before you start up a focus-trap session.



Samples










Summary


You may just find that some types of difficult/impossible shots become do-able with this technique. You wouldn’t make a steady diet of this kind of shooting, but when you need it you need it.


You may think that animals wouldn’t be any good at taking selfies with a DSLR, but they may just surprise you.










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