Railfan Technology > The Nikon D200 has a very interesting feature called Tr

In regards to the Nikon D200.
I've found a very interesting feature that could be very useful for railroad photography, its called "Trap Focusing" or, "Focus Priority auto shutter fire?"
Wouldn't it be cool if you could take a train picture hands free. You should be able to, with the Nikon D200
Say you have two cameras, the fist camera (D200) could be set up on a tripod, focused at just the right spot, the train comes along, and as soon as it comes into focus at the spot that you just set up, it fires the shutter. In the mean time, you are set up with your other camera at a different spot, different angle, different focal length lens, now you have two totally different pictures of the same train. Its like getting two shots for the price of one.
This outline was found on the Nikonians web site. Here's the set up for the D200.

<you can be in "S" or "C" modes. It will depend on your settings in a1 and a2.

<Set a2 to "Focus"
<Set a6 to "AF-ON Only"

<Set switch on side of camera to "S"

<Set your focus to the distance that you want your picture to be taken.

<Hold down the shutter release and when an object appears at the correct distance the shutter will fire. You can use this with <your camera on a tripod to catch a car coming around a bend in which case the car moves into the "trap". Alternatively you can
<set your macro lens at a particular focusing distance and then move in on your prey until the shutter fires.

I don't have the D200 yet, still waiting for B&H, but for those of you that have this camera, give this a try, and let use know if in fact it works. My guess is, you would need a long lens to limit the dof

This has been available from Nikon for sometime if you purchased the high dollar back for the camera. Birders have used the feature for some time when the hummingbird stops at the feeder the camera senses something in the focus zone and releases the shutter. I know it is available for the F4 but you have to purchase the date/data back upgrade for the camera to get it. It is nice to see it as standard equipment with the body of the D200. Now it might be possible to get a photo of a gopher popping out of the hole instead of just a blur of him dropping back down after seeing the camera on the tripod.

Canon also has this fire on focus feature on their 1-Series cameras through Personal Function 16. Note that for both systems, you have to be there pushing the shutter button. It won't operate without you.

-Justin
RapidsRail.com

The Nikon system will indeed work without direct contact with the camera. Make the set up, activate the shutter and walk away. No photo will be taken until something comes into focus at the point where the camera is focused. I wonder how much power will be consumed by the D200 if the camera is set up for 30 minutes or more. Perhaps the camera goes into a light sleep mode with minimal power useage. We need someone to try it and give us a report. I can see some railfan potential with it especially if the user can choose the focus sensor to activate the shutter.

EDIT: The trap focus for the Nikon film cameras will work automatically after being set up. I have not researched the digital system for the D200 to say for certain they are the same as the film cameras with the data back attached. If the shutter needs to be depressed then the 10 in electronic shutter release cables have a locking feature where you can push the release and then use a slider to hold it there.