How does AF system works when operated Remotely ?

[birdsofearth]

I have done lot of remote control photography using manual focus

system. In MF remote control photography, I used to pre-focus my lens

and then wait for the subject to pass thru the area where the lens is

focused and then trip the shutter.

 

I want to how does AF systems work when operated remotely, i.e.

shutter is tripped remotely(whatever method). How does the lens

focusing mechanism works here ? Assuming that you have pre-focused

your AF lens to the subject area, what happens if subject is slightly

out of focus ? Does the lens focuses automatically ? Or do you prefer

to have your 'focus locked' to the subject area ? Can anybody share

their field experience of remote control photography using AF system,

specically regarding 'focusing'?

[bobatkins]

If your subject is in the AF zone when you trip the shutter it will AF just fine. If it isn't, it will AF on whatever IS in the AF zone. MF is safer if you know where your subject will be, but then if you knew that you could use AF! Some cameras (not EOS) have a mode where you can set them up focused on a particular spot and when something moves into that spot and is in focus, the shutter will trip.

 

When I've used a long remote (not very often), I've prefocused and left the system in MF mode.

[bill_horn2]

I use a Radio Slave 4i made by Quantum Instruments. Bob is correct, in AF mode the lens refocuses onto whatever is in the focus area. I shoot birds, and the system works, as advertised. However, it is much harder than you might imagine to "prefocus" on small, animate objects and get quality results. MF has proven a bit more effective for me too. Good luck!!

[chuck_greene]

Narendra,

 

Have you considering using one of Nikon's multi-function backs that include a "freeze" focus function?

 

You turn AF off on the camera (or lens) and focus the lens at a particular point, when something is in the line of sight of the focus sensor AND is at the same distance the lens is focused at, the back tells the camera to trip the shutter.

[patrick_clow]

Basically the camera will perform whatever function you have set it to do -- some newer cameras will NOT fire until the subject area has something is in focus. That, like setting to manual or auto mode, is purely a function of the settings available in your camera. Set to normal autofocus the camera will focus, then fire. Set to manual mode the camera will simply fire at wherever you focused. I have heard a rumor (anyone else heard of this?) that there is at least one autofocus camera that will fire when something actually comes into focus!

 

If timing is critical then you may not want to move the lens when it is in autofocus mode! Say you preset the camera by maunally moving the focus ring to a good point and you leave the camera in auto mode (most cameras do NOT recommend this!. Some cameras will move throughout the entire range of focus if they have been moved manually and the subject may clear the area before the camera settles on a focus. You'll have to experiment with your particular camera.

 

Another way to handle this is to "pre-release" the camera. With the right kind of cable for your remote you can turn on or off the wakeup function (like depressing the shutter release part-way). If you have your camera set to continuously autofocus, and the pre-release function is enabled, the camera will constantly focus and fire very quickly. This eats camera batteries like crazy! Maybe a few hours maximum operating time when used in this fashion.

 

I have worked with a lot of basketball shooters. They just about always pre-focus and set their remote cameras to manual -- even their F5s! But that's basketball and the "sweet spot" is pretty clear -- the goal is only so big. If you were setting up a camera at the end of a long corridor and the subject could be anywhere in it, that would be another problem.

 

Yet another method is to use a beam break device to fire the camera. Check out the WaveSensor at:

 

http://www.lpadesign.com/

 

Hope some of this is helpful!

[bill_harris1]

Nikon has a system on one of their backs(i forget the model #)that will fire auto only when a moving object comes into a prefocused area. They are good for shooting wildlife, birds,etc. The backs are rather expensive though, but they do a lot of fancy stuff and are somewhat specialized equiptment. Probably MF is the best option.

[rollin_verlinde]

just my 0.02 Belgian franks : the focus-triggering which was mentioned in the mail before is the f90x (n90s) with (I think) a MF26 back. However, the F100 can do this without an additional back. You can use this system only in good light conditions and slow-moving objects, otherwise the shutter goes off when the object is back out of focus. But it works!

 

I work a lot in dark environments, capturing flying bats on film and the only way to do this is MF, open shutter and a superfast IR-trigger on the flashes. Also when the object is in daylight and moving with an average speed, whatever that is, I think you will have more succes with MF than AF. Sometimes I try AF when photographing woodpeckers at branches sitting still and succes-rate is only slightly better.

Succes!

Rollin