Peterff Loc: O'er The Hills and Far Away, in Themyscira.

We've had a lot of discussions about the merits of manual focus with long lenses and also macro photography, and also for other situations.
Some have expressed frustration as a result of eyesight issues and other things. I haven't found much discussion about the capabilities some DSLRs - or other digital autofocus cameras that support manual focus modes - to fire the shutter when a focus point locks on.

This isn't intended as a brand comparison question, but more about the value or otherwise of this functionality, and especially from those that have experience with it one way or another.

Definition from wikipedia:

A method variously referred to as trap focus, focus trap, or catch-in-focus uses autofocus to take a shot when a subject moves into the focal plane (at the relevant focal point); this can be used to get a focused shot of a rapidly moving object, particularly in sports or wildlife photography, or alternatively to set a "trap" so that a shot can automatically be taken without a person present. This is done by using AF to detect but not set focus – using manual focus to set focus (or switching to manual after focus has been set) but then using focus priority to detect focus and only release the shutter when an object is in focus.

Background:

I was playing around with some old manual focus lenses that I have adapted to the EOS system with Ed Mika's replacement mounts. Specifically a Canon FL 55mm f/1.2 and a Canon FDn 135mm f/2, both equipped with chips to communicate with the camera, and thus provide focus detection. The camera is a Canon T3i with Magic Lantern v2.3 installed. http://www.magiclantern.fm/index.html

My primary interest in Magic Lantern relates to still photography not video. It provides capabilities such as extended exposure bracketing (for HDR for example), an intervalometer ( time lapse ), focus trapping and much more.

The focus trapping works with either fully manual lenses (with a chip installed for Canon) or with autofocus lenses in manual mode so long as the camera will recognize the lens aperture, and in this case is < f/8.

Essentially you compose your shot with (in my case using center focus point only), hold down the shutter and slowly adjust the focus. As soon as focus is achieved the shutter fires. This was using manual mode, so all other things needed to be set up ahead of time, but I believe that it will also work in other modes, at least with some lenses. The older ones need to be in stop down, manual mode.

Question:

I know that trap focus is supported on some cameras from some manufacturers, but it seems to be somewhat sporadic, at least that seems to be true for both Canon and Nikon. Magic Lantern is only 'supported' - better term is functional - on some Canon models.

So, ladies, gentlemen, and anyone that prefers a different affiliation, what do you think?

Thanks

Dngallagher Loc: Wilmington De.

Interesting, but would it not introduce more camera movement?

It would definitely take some getting used to for sure.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

Thanks. I think it could, but not necessarily so. I think it would be very situation dependent. For example, think birds at bird feeder, you sort of know where they might be, especially a humming bird. So if you have every thing set up, on a decent tripod, just waiting for the bird to trigger the shutter when in focus?

Or a moving subject traveling towards you. You know it will be in the trajectory, and the camera is triggered when focus is confirmed. The theory seems to be that the camera can respond faster than a human being, and possibly faster than continuous focus tracking.

Also, if you are in a well lit situation with high shutter speeds, but the action is predictable (to a photographer but not a camera), could it make sense?

This is why I'm asking about it, especially from anyone that has actual experience good or bad. I have only theory that tells me that it is interesting to explore. If some manufacturers or 'custom hackers' implement it , one assumes that it has some theoretical value, but that isn't necessarily guaranteed in reality. We still have cheap mirror lenses and people still buy them. "The debate goes ever on, from the forum where it began...."

Thanks for responding...., much appreciated.

nicksr1125 Loc: Mesa, AZ

On this same line, I'm looking at the Vello FreeWave Stryker Lightning & Motion Trigger to use with my Alpha 850. My use will be to set the camera up outside on our patio in a blind to shoot song birds as they land on the feeders. Do any of ya'll have any experience with this device?

blackest Loc: Ireland

pentax has it, saves missing and capturing a junk shot. Although there is a focus hexagon in the viewfinder too its solid when you have achieved focus.

I am not so keen on the idea of manually focusing as you hold down the shutter button you may start out in focus but your not going to stop before your out of focus either

Dngallagher Loc: Wilmington De.

I think that the way I read your note, I assumed composing, press & hold the shutter down and manually adjust the focus finishing up when the shutter fires, so that is where I would worry about camera movement.

Now, composing and pressing & holding shutter until a subject crosses the focus point to fire the shutter sounds like it would be good for some subjects, but I would think lots of things could set off the shutter, not necessarily what you might want, or they end up out of where you wanted them in the frame. Not sure.

RWR Loc: La Mesa, CA

Freeze-Focus is one of the functions of the MF-23 back for the Nikon F4 - great for auto unmanned/remote photography.

SharpShooter Loc: NorCal

I have shoot a lot on manual everything. Pre-focusing on an exact spot where I know the action will pass, especially with fast lenses wide open and then anticipating and shooting a spray of shots with the subject coming strait at me. If using long fast lenses, the DoF can be an inch or less in some shots. Even the bests cameras can't handle a shot like that and not likely to get the shot if the subject is traveling at say 40 mph or even as fast as 100 mph. The smaller the subject the harder.
Don't know if that's trap shooting.
Fast traveling subjects can move a few inches when coming straight at you by the time the camera locks focus and snaps the shot.
I'm not talking side to side movement, as the most basic camera can handle that.
I can post a shot later of what I'm talking about.
And manual lenses using the chiped adapters can't do it either. The chirp indicates the subject was in focus but not necessarily is any longer. I would NEVER depend on the chirp of a chipped adaptor for focus unless I have gobs of DoF. ;-)
SS

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

I think there are multiple ways of setting it up. I described just one. I believe Pentax may have been one of the first, possibly the first to implement this.

Thanks.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

Thanks SS. All valid points. Appreciated.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

I think this going to require experimentation. I suspect the camera reacts faster than I can. Both Don's and SS's points are good, but I can see some possibilities that may have potential, especially for the older manual focus lenses.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

Duplicate. Deleted.

Tjohn Loc: Inverness, FL formerly Arivaca, AZ

Yes, I have used to motion detector for large subjects, not birds, and it has worked perfectly. Meanwhile the light change detector was not working. It is in for repair or exchange by Vello. Past warranty and all, free repair, free return shipping. I did have to pay for my end shipping. I also have the Vello remote Freewave Plus and it works just fine.

sirlensalot Loc: Arizona

My old Pentax K-x had it. Tried it a few times. For the most part, it went unused. In fact, the AF was so erratic it was an option that would have helped had I made a choice to keep it.

GENorkus Loc: Washington Twp, Michigan

I've got two Pentax dslr's and both have the catch in focus. Used it on my older K20D and it worked well. The best results came when I had the most amount of boken. After a short while, I lost interest in it.