K7 & catch-in-focus... help!

Nass · 09-27-2009, 08:38 AM

Hello, I can't seem to get this to work as described in the manual, maybe I'm doing it wrong?

I've attached pentax-a 50mm, changed the focus mode to AF.S and focused on a spot 50 cm away. I pressed the shutter fully and moved something into focus immediately afterwards. It beeped (ie focus confirmation beep) but the camera didn't take a picture.

Then, I picked the camera up, pressed the shutter fully, moved the camera so that something became focused, and again it beeped but didn't take a picture.

However, if I press the shutter fully repeatedly, then when the camera does have focus, it takes the picture, but it prevents a picture being taken when when it's out of focus. In other words it's functioning like the camera has to be still and focused to take the picture (ie it's acting like an instantaneous mode that says "no focus? no picture") rather than 'catching' a subject when it comes into focus?

Is this what's supposed to happen or is there something else I'm supposed to do? I was under the impression that catch-in-focus is like a standby function that'll wait until a subject is in focus then take it (if shutter has been pressed). Is there some time within which the subject has to come into focus and if so, which setting would it be to increase that time?

Many thanks

Wheatfield · 09-27-2009, 10:28 AM

Catch-in focus was presented to us when Pentax first started making phase focus SLR cameras. It's more of an accidental feature than a real one, since it's just a quirk that is allowed by using a manual focus lens on an AF SLR camera.
Anyway, I think what you are probably running into is a combination of a more refined AF resolution combined with a slightly long lag time.
I've found with my K-7 (with AF lenses, AF-S) that if the focus locks but the subject moves out of focus before the camera takes the picture, I get exactly what you are describing as well.
My thoughts are that this was probably more usable 25 years ago when AF was new and sensor resolution wasn't as refined.

Here's a little check for you:
Put your camera on a tripod, set a focus distance, use a remote release to lock the shutter button and them walk towards the camera at different speeds to see how effective a feature catch in focus is.

Nass · 09-27-2009, 10:58 AM

Yes, upon further testing I think that's it - that you have to keep the shutter pressed fully down. Is this possible with an electronic remote control?

Wheatfield · 09-27-2009, 12:03 PM

Originally posted by Nass

Yes, upon further testing I think that's it - that you have to keep the shutter pressed fully down. Is this possible with an electronic remote control?

Oh, well yes, that helps. As soon as you release the shutter button, the camera stops trying to take a picture. The Pentax wired remote has a locking shutter button. I don't know if the third party ones do or not.

Nass · 09-27-2009, 12:31 PM

deleted, I was being dense

Nass · 09-27-2009, 12:36 PM

deleted - I was being even denser than usual

09-27-2009, 08:38 AM	#1
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402	K7 & catch-in-focus... help! Hello, I can't seem to get this to work as described in the manual, maybe I'm doing it wrong? I've attached pentax-a 50mm, changed the focus mode to AF.S and focused on a spot 50 cm away. I pressed the shutter fully and moved something into focus immediately afterwards. It beeped (ie focus confirmation beep) but the camera didn't take a picture. Then, I picked the camera up, pressed the shutter fully, moved the camera so that something became focused, and again it beeped but didn't take a picture. However, if I press the shutter fully repeatedly, then when the camera does have focus, it takes the picture, but it prevents a picture being taken when when it's out of focus. In other words it's functioning like the camera has to be still and focused to take the picture (ie it's acting like an instantaneous mode that says "no focus? no picture") rather than 'catching' a subject when it comes into focus? Is this what's supposed to happen or is there something else I'm supposed to do? I was under the impression that catch-in-focus is like a standby function that'll wait until a subject is in focus then take it (if shutter has been pressed). Is there some time within which the subject has to come into focus and if so, which setting would it be to increase that time? Many thanks

09-27-2009, 12:31 PM	#5
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402 Original Poster	deleted, I was being dense Last edited by Nass; 09-27-2009 at 12:37 PM.

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09-27-2009, 10:28 AM	#2
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,991	Catch-in focus was presented to us when Pentax first started making phase focus SLR cameras. It's more of an accidental feature than a real one, since it's just a quirk that is allowed by using a manual focus lens on an AF SLR camera. Anyway, I think what you are probably running into is a combination of a more refined AF resolution combined with a slightly long lag time. I've found with my K-7 (with AF lenses, AF-S) that if the focus locks but the subject moves out of focus before the camera takes the picture, I get exactly what you are describing as well. My thoughts are that this was probably more usable 25 years ago when AF was new and sensor resolution wasn't as refined. Here's a little check for you: Put your camera on a tripod, set a focus distance, use a remote release to lock the shutter button and them walk towards the camera at different speeds to see how effective a feature catch in focus is.

09-27-2009, 10:58 AM	#3
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402 Original Poster	Yes, upon further testing I think that's it - that you have to keep the shutter pressed fully down. Is this possible with an electronic remote control?

09-27-2009, 12:03 PM	#4
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,991	Originally posted by Nass Yes, upon further testing I think that's it - that you have to keep the shutter pressed fully down. Is this possible with an electronic remote control? Oh, well yes, that helps. As soon as you release the shutter button, the camera stops trying to take a picture. The Pentax wired remote has a locking shutter button. I don't know if the third party ones do or not.

09-27-2009, 12:36 PM	#6
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402 Original Poster	deleted - I was being even denser than usual