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How to use Trap-focus or Catch-in focus
Posted By: eurostar, 02-14-2009, 06:21 AM

Any Pentax DSLR allows the user to easily build a photographic trap to shot elusive birds and other animals. No need for infrared sensors and electronic do-it-yourself skills. Just a camera, a manual lens and a cable release with lock, and everyone can create a robot-camera that shot when the subject come on the spot. And the shot will be always in perfect focus.

You need: an AF Pentax reflex camera (a DSRL is preferable), a KA mount manual lens, an electrical cable release with lock and a tripod or similar camera support (pic 1).
Camera must be set on AF-S (pic 2), continuous shooting (pic 3), exposure mode on AV (pic 4). Aperture priority allows the use of a large aperture, with shallow DOF and fast shutter time to freeze movements.
Aim the central focus point to the place where your subject is expected to come, manual focus until focus aid (green hexagon) lit up, recompose to have the central focus point to aim at the point where subject head should be.
Now put viewfinder cap on, to avoid errors in exposure (pic 5)
Plug in the cable release (pic 6), push the release button and block it (pic 7).
Nothing will happens. Go to the place your subject will come, wave you hand in the focus point, and you will hear the shutter working.
Go away and allow subjects to come. After some hours come back and control if pictures counter advanced. If so, you can replay pictures on the LCD to see what species came.

With Pentax K20D, you can use not only the central AF point, but every one, allowing for a better placement of subject in the frame of the picture. This improvemetn has brought Pentax to rename the function catch-in focus.

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08-03-2015, 11:08 AM   #31
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Seems like Pentax haven't really thought this through. This should be a brilliant and easy to use feature for wildlife shooters, for example. Instead, only manual focus lenses? Having to tape foil over lens mounts? Fiddle endlessly with menu settings? It's all very Heath Robinson, when it should be so easy!
I thought this was the point of the feature, otherwise I can't see the point of it at all.

12-20-2015, 08:23 AM   #32
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I found the guidelines here very helpful. One small point may be helpful. The drive mode button on the K50 does not allow you to simultaneously set continuous shooting and use of the remote. However, I found - admittedly this may be obvious to others - that the wired remote will still works anyway. Also found it useful to pre-set the remote hold button before plugging in. It has taken a while but I think I am getting there! Many thanks for the advice in this thread.
04-27-2016, 10:19 AM   #33
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I do nt have a digital SLR yet and am educating myself about the K-1. So I was totally unaware of this trap-focus function. It's very appealing! However, although I saw on one of the Chinese reviews of the K-1 that the function is usable on the K-1 I can see no reference to it in the K-1 User Manual that I downloaded from the Ricoh site.

Please, can anyone point me to the relevant reference page in the User Manual? I searched using "CIF", "trap focus" and and "trap-focus" but found nothing.
Thanks in advance for any guidance.
04-27-2016, 10:41 AM   #34
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Since my first post I found it myself. I used "catch-in focus" and all was revealed!

07-22-2017, 08:29 PM   #35
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hi folks, i am just wondering, after all these years and all the fiddles, if there is a workaround for cif using a 200D, a Pentax 18-55II and/or a 70-300mm Sigma APO DG with no remote or adaptors or mount plates... shorting the terminal with tape seems so barbaric...

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