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11-09-2007, 07:20 AM   #1
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Expose ONLY when subject comes into focus.

Fairly new to the K10D so still learning. I understand that it is possible to set the camera up so that it will expose only when the subject comes into focus - useful for wildlife shots eg with the camera prefocussed on an empty space waiting for the beast to emerge from its lair. I believe I read something about it in this forum, but I can't locate the thread.

Any tips?

11-09-2007, 07:28 AM   #2
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Trap focus

QuoteOriginally posted by ukbluetooth Quote
Fairly new to the K10D so still learning. I understand that it is possible to set the camera up so that it will expose only when the subject comes into focus - useful for wildlife shots eg with the camera prefocussed on an empty space waiting for the beast to emerge from its lair. I believe I read something about it in this forum, but I can't locate the thread.

Any tips?
I've seen it also called focus trap, don't know which is right. Here is a thread on it. https://www.pentaxforums.com/forums/pentax-dslr-discussion/9853-trap-focus.html
I use it all the time with my manual lenses.

With screw mount, K, M, or A series lenses put switch in AFS mode. Hold shutter button down and turnfocus ring until it is in focus and the camera will fire. You can do it from a tripod using a remote lock so that it fires every time something comes in focus if you set the switch to AFC.

Regards,
ken

Last edited by regken; 11-09-2007 at 07:34 AM.
11-09-2007, 07:40 AM   #3
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Just be careful to turn the focusing ring VERY slowly. There is a bit of lag in the focus indicator, so it is easy to FF or BF using this technique. Of course, is that any different than when "eyeballing" it?
11-09-2007, 09:59 AM   #4
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If you search the DPReview pentax forum on the term "focus trap", you should find postings about this. Ron (brandrx) has quite a few posts on it.

The important thing to note is that you do this with the camera set on AF, but you are using a MF lens. You focus on some point that is out of focus and use a corded trigger to set the shutter open. There is a trick for using FA and DA lenses involving sliding a piece of paper between the pin contacts to prevent the circuitry from getting involved.

11-09-2007, 09:15 PM   #5
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I've usually called it snap-in-focus (as in the SF-1 manual). A couple up in the thread there is a typo where regken says to use AFC. This does not work. You must be in AFS - the shutter will not trip untilt he subject is in focus. If you are in AFC the shutter will go off, in focus or not.

I use this for shooting butterflies with my macro. I set the macro to the image size I want, set the camera to AFS and hold down the shutter release while slooowwwwly moving the camera toward the subject. (My macro is the M 100/4). This will work with any manual focus lens or AF lens that has an AF/MF switch or focus ring positiion. Just use the MF lens with the camera in AFS. Works every time.

I got three nice humming bird shots at a feeder when I fist got my SF-1 with the 70-210 just to see how it worked. Focussed on the perch, slid the AF spot up about an inch above the perch, set AFS, locked the cable release down, and went inside to eat supper. Eureka! It works! LOL
11-10-2007, 08:53 AM   #6
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Great - thanks for all your help folks. I will try it out.
11-12-2007, 08:54 PM   #7
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QuoteOriginally posted by Canada_Rockies Quote
I've usually called it snap-in-focus (as in the SF-1 manual)....

...

I got three nice humming bird shots at a feeder when I fist got my SF-1 with the 70-210 just to see how it worked. Focussed on the perch, slid the AF spot up about an inch above the perch, set AFS, locked the cable release down, and went inside to eat supper. Eureka! It works! LOL
Do you still use your SF-1?
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