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04-08-2008, 05:09 PM   #1
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K20D - Catch in focus - a backward step

The K20D has an option to turn on "catch in focus". So when using certain lenses it will automatically fire a picture when the image is in focus and your finger is on the button. This is fine except that it only works with manual focus lenses or DA or FA lenses that have a MF/AF setting on them. So too bad if you want to use a DA or FA lens in manual focus and the lens doen't have MF/AF on it.

My istDS had a setting something like - only take a picture when it's in focus On/Off. So if you set this on you do a "catch in focus" with ANY lens, and I used it with my DA 18-55.

To me this is a backward step by Pentax, limiting this useful feature to a certain amount of lenses, none of which I own!

04-08-2008, 07:38 PM   #2
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QuoteOriginally posted by Arpe Quote
The K20D has an option to turn on "catch in focus". So when using certain lenses it will automatically fire a picture when the image is in focus and your finger is on the button. This is fine except that it only works with manual focus lenses or DA or FA lenses that have a MF/AF setting on them. So too bad if you want to use a DA or FA lens in manual focus and the lens doen't have MF/AF on it.....

I have not used this feature on my K20D, but I suspect that there's a good reason for these limitations.

Pentax bodies are so remarkably compatible with nearly all old Pentax lenses that we Pentax users sometimes forget what it's like out there in the rest of the world, say, with Nikon and Canon bodies.

Will
04-09-2008, 12:40 AM   #3
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still....

QuoteOriginally posted by WMBP Quote
I have not used this feature on my K20D, but I suspect that there's a good reason for these limitations.

Pentax bodies are so remarkably compatible with nearly all old Pentax lenses that we Pentax users sometimes forget what it's like out there in the rest of the world, say, with Nikon and Canon bodies.

Will
the op has a point.

it does seem like a backwards step.
it may have its reasons...but...one generation of camera supporting any lens for trap focus

then the next only supporting a handful?
04-09-2008, 12:41 AM   #4
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QuoteOriginally posted by Arpe Quote
The K20D has an option to turn on "catch in focus". So when using certain lenses it will automatically fire a picture when the image is in focus and your finger is on the button. This is fine except that it only works with manual focus lenses or DA or FA lenses that have a MF/AF setting on them. So too bad if you want to use a DA or FA lens in manual focus and the lens doen't have MF/AF on it.

My istDS had a setting something like - only take a picture when it's in focus On/Off. So if you set this on you do a "catch in focus" with ANY lens, and I used it with my DA 18-55.

To me this is a backward step by Pentax, limiting this useful feature to a certain amount of lenses, none of which I own!
Do you mean that if you set the switch on camera body to MF it won't make a picture when something comes to focus and you are holding down the shutter ?

04-09-2008, 07:50 AM   #5
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QuoteOriginally posted by procyon Quote
Do you mean that if you set the switch on camera body to MF it won't make a picture when something comes to focus and you are holding down the shutter ?
Sounds like this only works on DA lenses w/ an MF button.

This was a major complaint w/ the K10D...what you want only works if the lens is not AF. The hack was to take a piece of scotch tape and cover the AF pin on the lens so the body thinks it is a MF lens. Then what you want can be done.

I don't understand why they implemented the K20D trap focus the way they did either...sounds like the hack will still be needed...
04-09-2008, 08:29 AM   #6
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I'm at work and can't try myself atm. but would the following work:
1. set the camera not to AF at shutter half press.
2. set focus mode to AF-S
3. press the shutter button completely down
4. focus manually until something is in focus
Does this make a DA lens trap the focus ?


Edit:
Never mind, doesn't work that way (at least on K10D, but I guess K20d should be the same).

Last edited by procyon; 04-09-2008 at 01:32 PM.
04-09-2008, 05:04 PM   #7
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QuoteOriginally posted by procyon Quote
Do you mean that if you set the switch on camera body to MF it won't make a picture when something comes to focus and you are holding down the shutter ?
That's right. It just takes it as soon as you press the button, from what I remember of my experiment at home a couple of nights ago.

It just seems strange to alter the istDs way of doing things when it did the same thing but better.
04-09-2008, 06:02 PM   #8
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I don't think you all understand or remember correctly...

Arpe wrote:
QuoteQuote:
My istDS had a setting something like - only take a picture when it's in focus On/Off. So if you set this on you do a "catch in focus" with ANY lens, and I used it with my DA 18-55.
I still have the *istDS. (That's all I have.) The trap focus setting Arpe describes above is the MF/AF switch on the body. And so it only works with manual focus lenses, even on the DS. Here's why:

MF - The shutter fires no matter how far OOF the scene in the viewfinder. It doesn't matter if you have a MF or AF lens.

AF - The shutter fires only when the focus is good enough to trigger the "in focus" circuit. With an AF lens, you are in AF mode so of course you can't set the focus manually. With a manual lens in AF mode, however the shutter still won't fire until it detects "in focus". So trap focus now works... The shutter only fires when the bug, bird, or what ever moves into the "in focus" region that you have set manually. Disabling the AF pin as kenyee suggested turns an AF lens into an MF only lens overcoming this "limitation".

procyon wrote:
QuoteQuote:
Do you mean that if you set the switch on camera body to MF it won't make a picture when something comes to focus and you are holding down the shutter ?
Right. In MF mode on the body, it takes the picture instantly and doesn't attempt decide if the scene is in focus or not. That's the purpose of the MF switch on the body.

So, AFAIK, the DS on up to the K20D all behave the same regarding "trap focus". By definition, you cannot use an AF lens (unless you disable the AF) regardless of body. No steps back here. Trap focus is a nice, probably unintended consequence / side effect of Pentax backwards compatibility with old MF only lenses.

See some old posts by BRANDRX (Ron) in the DPR forum for much more detailed info.

Regards.

-Mark

04-09-2008, 06:25 PM   #9
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QuoteOriginally posted by SWEngineer Quote
Arpe wrote:

I still have the *istDS. (That's all I have.) The trap focus setting Arpe describes above is the MF/AF switch on the body. And so it only works with manual focus lenses, even on the DS. Here's why:

MF - The shutter fires no matter how far OOF the scene in the viewfinder. It doesn't matter if you have a MF or AF lens.

AF - The shutter fires only when the focus is good enough to trigger the "in focus" circuit. With an AF lens, you are in AF mode so of course you can't set the focus manually. With a manual lens in AF mode, however the shutter still won't fire until it detects "in focus". So trap focus now works... The shutter only fires when the bug, bird, or what ever moves into the "in focus" region that you have set manually. Disabling the AF pin as kenyee suggested turns an AF lens into an MF only lens overcoming this "limitation".

procyon wrote:
Right. In MF mode on the body, it takes the picture instantly and doesn't attempt decide if the scene is in focus or not. That's the purpose of the MF switch on the body.

So, AFAIK, the DS on up to the K20D all behave the same regarding "trap focus". By definition, you cannot use an AF lens (unless you disable the AF) regardless of body. No steps back here. Trap focus is a nice, probably unintended consequence / side effect of Pentax backwards compatibility with old MF only lenses.

See some old posts by BRANDRX (Ron) in the DPR forum for much more detailed info.

Regards.

-Mark
This snap-in-focus system was introduced with the SF-1. If the lens is Manual Focus, the camera waits for something to pass through the focus point when the camera is set to AF.S only. AF.C and MF fire the shutter as soon as you press the release without reference to the state of focus.

Personally, I was disappointed that the DA* lenses I have do not do this when set to MF while the K10D remains in AF.S. I was hoping I would have the best of both worlds this way. Maybe on the K30D.
04-09-2008, 06:47 PM   #10
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QuoteOriginally posted by Canada_Rockies Quote
... Personally, I was disappointed that the DA* lenses I have do not do this when set to MF while the K10D remains in AF.S. I was hoping I would have the best of both worlds this way. Maybe on the K30D.
The DA* lenses have a MF/AF switch on them? (Obviously I haven't gotten very near such a lens.) Then I can understand your disappointment that trap focus doesn't work with the switch on the lens set to MF and the body to AF.S. But none of my DA lenses (such as the DA18-55) have such a switch and so they cannot be expected to "focus trap" much to Arpe's disappointment.

-Mark
04-09-2008, 06:48 PM   #11
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QuoteOriginally posted by SWEngineer Quote
The DA* lenses have a MF/AF switch on them? (Obviously I haven't gotten very near such a lens.) Then I can understand your disappointment that trap focus doesn't work with the switch on the lens set to MF and the body to AF.S. But none of my DA lenses (such as the DA18-55) have such a switch and so they cannot be expected to "focus trap" much to Arpe's disappointment.

-Mark
Yes, but unfortunately they act just like the switch on the body. PITA. Annoying, yet.
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