Which Lens for Catch-In Focus Mode?

stewart_photo · 12-22-2008, 09:39 PM

Here's a question for the experienced users of the Catch-In Focus Mode of the K20D. An unusually attractive bird is visiting my feeder roughly three feet from the window, so this is perhaps a good time to experiment with this mode. As I understand it, I need either a DA or FA lens with a AF/MF switch or a manual focus lens.

So what's a reasonably priced lens adequate for this purpose? Please note I don't want to spend a lot of money at this time since this is strictly experimentation and I don't really need this type of lens elsewhere.

By the way, while I have your attention, any other tricks or tidbits of advice you can offer when it comes to doing this? Thanks for your kind assistance.

stewart

**Marc Sabatella** · 12-22-2008, 09:48 PM

If you don't have an M135/3.5, that would seem an obvious cheap possibility. Unless you're worried that's too long, in which case, an M100/2.8 isn't *that* much more expensive. Or, if you don't have a 50, that would be another obvious thing to have.

axl · 12-23-2008, 01:01 AM

How does this mode work? Does K10 have it too?
anyway, with 3 feet, I think 135 will be too long. Something between 70 and 105 would be long enough,
my 2p

Gimbal · 12-23-2008, 04:42 AM

Yes, it’s works on the K10 too.
It’s not a special mode in a menu or something, but with a manual lens and the camera set on auto focus the shutter will not release until there is something in focus.

**Marc Sabatella** · 12-23-2008, 11:44 AM

Originally Posted by axl

How does this mode work? Does K10 have it too?

As far as I know, all Pentax DSLRs have it. When using a manual focus lens - and it has to be an manual focus lens, or at least an AF lens in which the AF can be disabled *on the lens* - set the camera to AF. Camera won't fire unless it thinks subject is in focus. So Press and hold shutter, then start slowly turning the focusing ring. When the camera thinks it is in focus, it fires. Or, prefocus on a spot where there is nothing to focus on. Press and hold the shutter. When an appropriate subject comes to that spot, the camera notices something is in focus, and fires.

*jbinpg* · 12-23-2008, 12:53 PM

Originally Posted by Marc Sabatella

As far as I know, all Pentax DSLRs have it. When using a manual focus lens - and it has to be an manual focus lens, or at least an AF lens in which the AF can be disabled *on the lens* - set the camera to AF. Camera won't fire unless it thinks subject is in focus. So Press and hold shutter, then start slowly turning the focusing ring. When the camera thinks it is in focus, it fires. Or, prefocus on a spot where there is nothing to focus on. Press and hold the shutter. When an appropriate subject comes to that spot, the camera notices something is in focus, and fires.

Just confirming what Mark said: if you have a fancy new DA* such as my 300, if you leave the body set to AF but turn the lens switch to MF, then the lens will do catch-in focus. Quite handy for those times you need to have the subject trigger the shot.

Jack.

stewart_photo · 12-24-2008, 01:29 AM

Thanks for the suggestions everyone. I borrowed an older manual focus zoom from a friend and will do a little expermenting the next time that bird appears. If it works out, maybe I'll buy a lens myself. I have already learned one thing. A well charged battery is an absolute necessity, with an AC adapter perhaps a good idea.

stewart

*Syb* · 12-24-2008, 01:49 AM

Does this Autofocus mode on the camera need to be AF-C or AF-S?

flyer · 12-24-2008, 02:58 AM

The camera needs to be on AF-S, otherwise it won't work.

*Syb* · 12-24-2008, 03:17 AM

Originally Posted by jbinpg

Just confirming what Mark said: if you have a fancy new DA* such as my 300, if you leave the body set to AF but turn the lens switch to MF, then the lens will do catch-in focus. Quite handy for those times you need to have the subject trigger the shot.

Cool! What if it doesn't work? My K10d does not wait for anything to come in focus but fires straight away. Is there a custom setting I could have forgot to change?

My camera is in AF-S mode.
The lens is MF.

What could be wrong?

*Syb* · 12-24-2008, 03:35 AM

Let's elaborate.

K10d; AF-S mode and AF-button for autofocus. This will work with the K135/2.5:
Pressing the AF button while turning the focusing ring will make this a catch-in-focus combo.

But... it will not work with a DA or a FA lens, when they are set MF.
Pushing the AF button on the back (lens will of course do nothing) but shutter fires away happily and unsharp.

*falconeye* · 12-24-2008, 04:01 AM

Originally Posted by stewart_photo

any other tricks or tidbits of advice

Experimenting with a tele converter, I noticed that the contacts on the lens' bayonett can be taped such that a FA or DA lens becomes non-AF.

You may use an old (non-AF) tele converter as well.

You may find some extra info in some of my posts in the teleconverter thread:
http://www.pentaxforums.com/forums/243751-post330.html
http://www.pentaxforums.com/forums/243776-post331.html

danielchtong · 12-24-2008, 07:26 AM

Originally Posted by stewart_photo

Here's a question for the experienced users of the Catch-In Focus Mode of the K20D. An unusually attractive bird is visiting my feeder roughly three feet from the window, so this is perhaps a good time to experiment with this mode. As I understand it, I need either a DA or FA lens with a AF/MF switch or a manual focus lens.

So what's a reasonably priced lens adequate for this purpose? Please note I don't want to spend a lot of money at this time since this is strictly experimentation and I don't really need this type of lens elsewhere.

By the way, while I have your attention, any other tricks or tidbits of advice you can offer when it comes to doing this? Thanks for your kind assistance.

stewart

I had lengthy discussion on this focus trap (or catch in focus) method and Ron (further down this thread) explains how it works.

BIF ok with manual focus lens: Pentax SLR Talk Forum: Digital Photography Review

Focus trap method is very good for not quite fast subject , say kids walking to you. But for fast one like bird flying or sport car zooming from one end to next the manual method (a tricky one) is still preferred (maybe by me then). The main problem lies with the camera not responding and confirming fast enough.

Daniel

navcom · 12-24-2008, 09:34 AM

Holy crap! I learn something new here every day! I've used manual lenses on my DSLR's for years and have never tried this. How cool is this!

Yeah, it's pretty easy to make me happy.

*Andi Lo* · 12-24-2008, 12:45 PM

Does K100 have this feature? I'm pretty sure I read the magic lantern manual extensively and cannot find the word "catch-in focus"