Focus Trap??? Which cameras can I use focus trap with?

[haring]

- Is focus trap a feature of the lens or the camera? I am sorry if the question is too basic.-
- Is there a list of DSLRs I can use "focus trap" with? Canon, Nikon, Sony, Leica, Mamiya, Hasselblad, etc...?
- Can I use with any lens on cameras which capable of the focus trap feature?

I have a few old manual lenses and it would be great to focus on moving subjects...

Thanks a lot!

 

[ann]

is this a digital question? wrong site.

On the other hand, never heard the term focus trap. Do you mean auto focus lock? If so, this is a feature of the camera not the lens. Most older manual lenses will not match up with the auto focusing features of chip driven bodies, either film or digital.

 

[munz6869]

Yes, wrong site. If you were shooting film, the Canon EOS 1V has the ability to focus trap - it's 'personal function 16', and means that when you press the shutter button, the shutter will only fire when there's an object at the focussed point of the lens.

Marc!

 

[Jeff Kubach]

I sometimes use hyperfocal.

Jeff

 

[film_man]

Assuming that by focus trap you mean pressing the shutter button and then the camera not firing until it thinks it is in focus, then as far as I know and I have used, this is only possible with digital SLRs and cameras like the EOS 1V when using AF lenses. Manual lenses will cause the camera to fire immediately.

 

[ann]

interesting, learn something new everyday

 

[ath]

http://www.eosdoc.com/manuals/?q=ATrapFocus

 

[53bicycles]

My Pentax K10d (dslr) has the focus trap trick. It works great, and works on manual lenses also.
Not sure if the current K5 has it, but I belive Pentax is pretty well known for this feature.
Just set the focus dial to "AF-S" and the shutter will only fire when the center focus point is sharp.
Works well for sports, macro, journalism, and most everyday use.
You can hold the shutter and wait for the subject to move into your preset focus plane.
Also you can hold the shutter down while focusing and it will fire when sharp.

 

[Francis in VT]

I remember selling the Yashica 230 AF camera which had Trap Focus.
I'm not sure but I think one of the Mamiya 35 electronic models also had it .

This is an explanation from the manual for the Yashica 230.


Trap Focus:
This mode is useful for shooting nervous animals or moving subjects at a fixed distance. Face the camera toward the place where you guess your subject will come, set the camera to that distance with the Focusing Ring, attach the cable switch and release it. As soon as the subject comes to this distance and it is caught in the focusing frame in the center of the viewfinder, the shutter will trip to take your picture.

Francis in VT

 

[Usagi]

nikon f90x has focus trap when equpment with multifunction back.

With af lenses the camera fires when something goes to focus. I haven't have tested with mf lenses.

 

[Rick A]

Where's the skill in that feature? I'll stick with my "I'll do it myself" cameras

 

[Diapositivo]

IIRC the first camera with focus trap was an Olympus of the OM system which had assisted focusing, it was a derivated of the OM-10. For those who don't remember, before autofocus there was assisted focusing, and it was good for those who were somehow sight-challenged. Instead of relying on microprisms or such, your camera gave you three leds in the viewfinder, one pointing to the right, one to the left, and another one telling you focus was OK. If you forgot your glasses in your car, or had to use somebody else's camera without a dioptre, well that might have helped. Also it made things like focus trap possible.

The first such camera was IIRC an Olympus based on the OM-10, followed a few months later by a Canon model (some kind of modified AV-1 maybe). The Olympus surely had this "focus trap" thing, which obviously worked with any manual focus lens (autofocus lenses were yet to come).

In the autofocus field, Nikon F-801 should have had the "focus trap" function with an optional "data back" that performed many functions besides impressing the date.

So, to answer the questions of the OP: focus trap is a function of the camera, which must have some electronic focus detection capability.
If the camera is an assisted-focus camera, it would work with any lens for that camera (manual focus lens, that is).
If the camera is an autofocus camera, you have to see it case by case but I would guess it would work with any lens anyway if the mount is the same (Nikon, Pentax) so that you don't need an adapter ring.

Autofocus devices don't like stopped-down diaphragms so it would probably not work properly with a stopped-down lens of a different make used with an adapter ring unless you use it at a fairly wide aperture.

Fabrizio

 

[moki]

There is a trick to do it with a Canon EOS... put a little piece of tape (something thin like scotch tape seems to work) over the rightmost electric contact on the lens. In this picture (->link) you see from left to right the row of small contacts, then the one that's a little bigger and then finally the small one you need to isolate. My lenses only seem to have a row of five contacts, not nine, but it's still the one on the very right and it seems to control the autofocus motor. Attach the lens as usual, set autofocus to "one shot", manually prefocus to whatever distance you want and press the shutter. The camera will try to focus, but can't because the contact is blocked. It won't open the shutter until there's something in focus, but since autofocus is dead, it will go off as soon as something wanders into the focus trap. You're basically killing autofocus in the lens without the camera knowing about it.
It doesn't work with all lenses, though... I have no idea, why this is happening. With a Tamron 60mm macro for digital cameras and it didn't work, but older Zooms by Canon, Tamron and Soligor worked very well with EOS 50e and 50d and probably with all other EOSses too. Usually, focus trap is a property of the camera, but this is a workaround.

This neat little trick was discovered or at least documented by Jan Berenbrink on his website: http://www.berenbrink.net/node/23 There's a more in-depth description if you speak german.

 

[narsuitus]

Here is my understanding of the “trap focus” feature of some auto focus cameras and/or lenses:

1. The photographer pre-sets a focus distance (20 feet for example).

2. The camera pre-focuses at that 20-foot distance.

3. The auto focus of the camera delays the shutter release until there is an in-focus subject at that 20-foot distance.

4. The camera automatically releases the shutter to take the photo (with or without the presence of the photographer) when an in-focus subject is at the 20-foot distance.

Since this is an auto focus feature, it can theoretically be in film or digital cameras.

 

[David A. Goldfarb]

Not a technique I've used, but I'd say there are certainly skills associated with techniques like remote-camera nature photography that use methods like trap-focus, animal triggers, and such. Some photographs can't be made any other way, and it takes considerable knowledge of the subject's habits and feeding patterns and forethought with regard to lighting and background placement to be "lucky" enough to get a good shot that way.

 

[Diapositivo]

The Yashica 230 AF and the Yashica 200 AF had the focus trap function as well. I even forgot that there had been Autofocus Yashica SLRs, I've just been browsing an old catalogue of 1989.

Fabrizio

 

[haring]

nikon f90x has focus trap when equpment with multifunction back.

With af lenses the camera fires when something goes to focus. I haven't have tested with mf lenses.

I have tried with my old MF lenses and it doesn't seem to work. I just don't want to waste film.... I better use my digital cameras and AF lenses.