Trap Focus with manual lens
4 Sep 2013 -
Trap focus doesn't work with manual lenses for Nikon (or Canon as far as I'm aware). Trap focus is a method where you set the camera to focus on a specific spot and as soon as it detects focus on something entering that zone, it fires of an exposure. Unfortunately, this requires an autofocus lens for unknown reasons. The camera is perfectly capable to detect whether or not there is an object in focus on a manual lens, but it won't let you expose only if such an event occurs. When depressing the shutter button on a manual lens, it always fires of a shot.
But, there is a solution in the shape of an AF-chip that you glue on to the manual lens. I have a Lensbaby Composer Pro and the reason I want to use trap focus is because the lenses for the Lensbaby sometimes heavily distorts the image in the viewfinder so it's hard to determine whether or not you're in focus or not. But the camera knows, most of the time at least! So I ordered a Dandelion chip and here are the steps to mount it.
For reference, here's the connection of a normal lens
This is my Composer Pro, lacking the above connections since it's a manual lens.
These are the parts that came in the Chip kit. A template for placement and a small plastic mounting bracket when needed.
The chip was glued to the plastic mounting part, which was needed in my case since the Composer Pro has a part of the metal missing where the chip should be mounted.
Then I removed the mounting piece from the lens and with the template I glued the chip. The template slides in to a grove on the lens which ensures that the chip is placed 100% correct.
Then I assembled it all together, and here's how it looks
And it works! The camera now thinks it has a autofocus lens mounted, and won't fire off the shutter unless it detects focus. Sure, it requires some practicing, since you can overshoot the focus point since you are focusing manually, but I'm very pleased!
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