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!

[Aegea]

I think it's really a feature of both. On my D90, the camera has to be able to detect focus, which means that the lens has to be fast enough/the light has to be bright enough. Below about f/8 (e.g., an f/6.3 lens with a 1.4x TC) focus trap will not work reliably, if at all. Seems to be no essential difference between MF and AF lenses. I'm sure others on the forum have a better understanding than I do, however.

[jojonac]

I had no Idea what focus trap was.

So I googled it. From the top two results I would say that its a function of the camera. And it looks like any new Nikon from the D2H and up will do it. Seems like a neat idea, but with todays AF motors and AF systems it almost seems like to much trouble for what its worth.

jojo

[dlambert]

I think CHDK can accomplish something like this on supported cameras, but it sounds like it's a little bit of a hack.

[i speak in math]

i believe any pentax dslr can do it so long as the lens is manual focus or has a manual focus switch on the lens. This is really helpful for all of us that can and do use old glass.

[daft_biker]

Originally Posted by haring

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

Pre-focus?

I use manual focus lenses on moving subjects frequently.....no need to let the camera do it for you. I also use the pre-focus technique with compacts to get the shutter lag down.

[inkista]

Canon's don't do focus trap (about which I am sad). There's a weird hack to approximate it, but it's not the same thing.

Nikons and Pentaxes do, iirc. Not sure about the others.

[jdepould]

Originally Posted by daft_biker

Pre-focus?

I use manual focus lenses on moving subjects frequently.....no need to let the camera do it for you. I also use the pre-focus technique with compacts to get the shutter lag down.

It's sort of like prefocus.

You set the camera to focus-priority release, then prefocus on the spot where you want to shoot. Flip it into continuous and hold the shutter down. Any time an object is in focus the shutter will release.

[daft_biker]

Originally Posted by jdepould

It's sort of like prefocus.

Whilst I'm sure it has it's uses when something is coming straight at you and fast I can't imagine it's that useful when side on and trying to time the moment....



.....if I'd have panned in following the movement with focus trap the shutter would have fired way too early.

Focus trap would probably work well with something like...

....which I also used manual focus for as I happened to have a manual focus lens on at the time. Focus trap would have probably got me a better hit rate, made it easier to fill more of the frame and get shallower DoF (not that it really matters for snaps of the bairn) .

Don't have it but am guessing it has it's uses and limitations?

PS both shots above taken using pre-focus