Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-25-2008, 08:39 PM   #16
Veteran Member




Join Date: Aug 2008
Location: California
Posts: 851
Original Poster
Thanks for your thoughts. I was at a shop today with my gear so I borrowed a K20d to test. I can confirm that it works with my DA* lenses set to MF. I was not really near any moving targets so I could not test the speed/accuracy but at least it works in theory with those lenses.

09-26-2008, 04:22 PM   #17
Site Supporter
LeoTaylor's Avatar

Join Date: Feb 2007
Location: Connecticut
Photos: Gallery
Posts: 679
It is nice that the K20D has a Catch In Focus Mode. This differs from my thread called, "Trap Focus Setup for K100D" in that the it appears the newer camera takes one shot and releases the shutter. Perhaps you can lock the shutter with a cable release? The older camera takes more effort to set up but keeps shooting as long as enabled. This allows capturing fleeting events like squirrels in my case or hummingbirds as others have done. You need dozens of frames to get a few interesting ones. The last image on this thread was one of 930 taken automatically in 90 minutes....

https://www.pentaxforums.com/forums/pentax-dslr-discussion/16946-trap-focus-setup-k100d.html
09-27-2008, 01:12 PM   #18
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,144
QuoteOriginally posted by Deni Quote
Yes, it'll do just that but only with manual only lenses or if you place a piece of paper between the contacts of the lens and camera for af lenses.

As you turn the focus ring and hold the shutter button pressed the camera will fire only when the subject in the center will be in focus.

Disadvantages:

If you use very slow shutter speeds it might not work as when the subject is in focus, the camera fires, and as the shutter is still opened you might not react that fast and you still keep turning the focusing ring.

This won't work if you want your subject to be off the center because if you recompose you have to have the camera set to MF so that it would fire when the centerpoint is off focus.
The OP is talking about the k20d, and catch-in-focus can be enabled by setting the body to AF.S and the lens to MF. It's the first thing I tried with my DA* 50-135 on the k10d, and it did not work. I bitched, and Pentax fixed it - but only on the k20d.

It works beautifully on the k10d with my M 100, M 400 and A 70-210. But it won't work with the DA* lenses. I blew the budget when I got the k10d last November, unfortunately, so I cannot upgrade to the k20d ... yet.

I can say that it is much faster reacting than autofocus - the time to focus the lens is eliminated. As soon as the focus is detected, the shutter is released. The camera does not need the time to focus the lens.
10-05-2008, 03:17 PM   #19
Veteran Member




Join Date: Aug 2008
Location: California
Posts: 851
Original Poster
For anyone interested I thought i would follow up on this and let people know my experience with this catch-in-focus.
I picked up a K20 to shoot an event today and it went quite well... but not perfect.

setup: DA*50-135, shot at F3.2, 1/1000, whatever ISO required to reach those settings.

I went out the day before to dial in all the settings and try it out. I sat near the bottom of a hill that had a lot of cyclists coming down (~30mph) and tried to autofocus to capture them at close to full frame. The autofocus failed miserably. 10/10 failure rate. the Pentax AF is simply not fast enough to capture.

Catch in Focus - I set it up by trying to catch the cyclist in the perfect position using AF (which of course came out blurry). I then set the AF to AF.S and the lens to M. I pointed the camera at the next cyclist with the shutter release fully depressed and followed them all the way down the hill. 10/10 times the shutter released with the cyclist in perfect focus



During the event the cycling was nearly perfect... probably close to 95%. Ocassionally it would mis-fire when nothing in the frame was anywhere near in focus. Then I changed to another location and shot the run. I don't know if it had to do with the fact that the new location had the runners in full sun (running into the sun) but the catch-in-focus was <50%. After a bunch of failures I tested it out by depressing the shutter release halfway and watching for the in-focus "dot" to appear. That dot would frequently appear 3 different times at different distances (while the focus on the lens was not changing). I started to feel a little panicky thinking that the camera was going to let me down and ruin a whole section of the race so I tried switching to autofocus, figuring that the runners were going significantly slower than the cyclists so maybe it could keep up. For the most part the AF.C worked well with close to ~75% in perfect focus with another 10% just a little soft (but probably still OK).

There are a few reasons I can think why I may have been having a little trouble on the run.
1. the bouncing motion of the runners was somehow messing with the AF computer
2. The direct sunlight (lots of runners had white jerseys) caused a near blow-out situation and the AF may have had a tough time with it.

In the end everything worked out. The catch-in-focus was positively brilliant on the cycling while the AF.C seemed adequate for the run. Clearly Pentax has some room for improvement with their AF but for now (with only some minor adjustments to technique) everything seems to be working out.

10-05-2008, 04:06 PM   #20
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,144
Your results seem to follow mine. I have been using snap-in-focus (former term dating from the SF-1) and the shutter release time is short enough that for fast action, it works very well.

Your failure rate with the runners seems a bit odd to me. I did read that the sun was behind you correctly? As a thought, and only because you did not mention it, have you set the camera to center spot only? I have the k10d, and with manual focus lenses it does that anyway, but perhaps with the newer lenses it is trying more than one focus spot.

Thanks for the review. This type of thing is greatly appreciated.
10-05-2008, 05:15 PM   #21
Veteran Member




Join Date: Aug 2008
Location: California
Posts: 851
Original Poster
My failure rate on the running really surprised me as well considering how it did on the bike. You are correct - the sun was on my back and in the face of the runners. the K20 has the same 9 focus points as the k10. The focus point was one point right of center (with the BG2 mounted that put the focus on the face of the rider/runner)
10-07-2008, 09:55 PM   #22
Site Supporter




Join Date: Sep 2007
Location: Victoria, BC, Canada
Photos: Gallery
Posts: 154
Trap focus with macros?

Has anyone here had good results using this trap focus technique when shooting macros? I just did a quick test and the concept seems to work if I close focus my lens then move in until it is in focus.
10-08-2008, 08:50 AM   #23
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,144
QuoteOriginally posted by Hornet Quote
Has anyone here had good results using this trap focus technique when shooting macros? I just did a quick test and the concept seems to work if I close focus my lens then move in until it is in focus.
It works beautifully with my M 100/4 macro. The only catch is that the focus point is always in the centre of the frame. Sometimes it would be nicer to have it off centre, but with an M lens I only have one working point of focus. I think. Hmmm gotta check THAT out.

10-09-2008, 05:10 AM   #24
Forum Member
LittleSkink's Avatar

Join Date: Jul 2008
Location: Sheffield, England
Posts: 63
QuoteOriginally posted by Hornet Quote
Has anyone here had good results using this trap focus technique when shooting macros? I just did a quick test and the concept seems to work if I close focus my lens then move in until it is in focus.
reckon it depends on your subject and whether the focus point wants to be in the middle (front to back) of the zone of focus

I tried 'trap focus' macro with my K10 on feeding bees and butterflies recently and found I got better results going back to MF and continuous shooting mode

Mostly 'trap focus' failed my needs here because the wrong stuff was in focus - in this instance. The focus was on the bee for sure, but the flower was far more out of focus than I wanted (was shooting hand held f8 mostly, with more light and f16 maybe this would be less of an issue)

When the bees took flight the trap focus was good for focus but exposure was only c1/90, so the buggers were blurred anyhow . . .

Last edited by LittleSkink; 10-09-2008 at 05:10 AM. Reason: typo
12-24-2008, 04:39 PM   #25
Pentaxian
Transit's Avatar

Join Date: Aug 2007
Location: Whanganui NZ
Photos: Gallery | Albums
Posts: 3,880
Hi Guys and Merry Christmas
excuse me winding up an old thread
I am trying to get trap focus happening with my K100D and an M- 200mm.
Have camera on AF but it fires whether focused or not.
Am I missing something ?
cheers
Pete
12-24-2008, 04:44 PM   #26
Veteran Member




Join Date: Apr 2008
Location: Minnesota
Photos: Gallery
Posts: 1,530
You need to make sure the AF mode is in AF.S.
12-24-2008, 05:04 PM   #27
Pentaxian
Transit's Avatar

Join Date: Aug 2007
Location: Whanganui NZ
Photos: Gallery | Albums
Posts: 3,880
and 5 mins later from the other side of the world comes the answer !
Thanks a lot MrApollinax, that did the trick

cheers
Pete
02-08-2009, 02:52 AM   #28
Senior Member




Join Date: Jan 2009
Posts: 173
I guess I'll have to revive the old thread as well.
I have a similar problem as the poster above me had, but my AF is set to AF.S, my camera is set to AF, but when I press the shutter release button is just fires without the subject coming into focus.

I am using Takumar 135mm (may be i need to short the contacts to get it to work?) and I tried it on M setting and Auto setting. Anybody have any ideas why it doesn't work? Oh and I'm using K200D
02-08-2009, 04:03 AM   #29
Senior Member




Join Date: Feb 2008
Location: London
Posts: 219
I think I'm being thick here, why does this require a new 'mode'? Using AF on the K10 with any of the manual lenses I had allowed me to use focus trapping - what does this mode achieve?
02-08-2009, 09:46 AM   #30
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,144
QuoteOriginally posted by Vormulac Quote
I think I'm being thick here, why does this require a new 'mode'? Using AF on the K10 with any of the manual lenses I had allowed me to use focus trapping - what does this mode achieve?
Unlike the K10D, on the K20D catch-in-focus will work with an AF lens that has a MF/AF switch on it. Set the lens to MF, the body to AF and catch-in-focus works. On my K10D, only MF lenses will use the old snap-in-focus system.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, k20d, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to use Trap-focus or Catch-in focus eurostar Pentax DSLR and Camera Articles 33 04-27-2016 10:41 AM
How to do catch in focus with Kx and 55-300? pjr Pentax DSLR Discussion 1 07-30-2010 08:09 PM
catch in focus? janstew Pentax DSLR Discussion 40 03-15-2010 05:02 PM
K-7 Catch in Focus konraDarnok Pentax DSLR Discussion 3 10-18-2009 01:26 PM
My first results with catch-in focus Rense Post Your Photos! 19 08-15-2009 12:16 AM



All times are GMT -7. The time now is 09:17 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top