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06-29-2009, 09:23 AM   #1
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Two K20D focus question

Two K20D focus questions:

1. On page 106 of the manual there are directions on how to make auto focus adjustments for different lenses. Step #3 relates how to make the changes apply to one lens or to all lenses. In the “Apply One” box it is stated: “The lens ID is displayed when obtained.” Question – how is it obtained? (Under Rec Mode, "Input Focal Length" is not active.)


2. In the camera Custom Menu screens, #34 is labeled “Catch-in Focus.” Clicking the four-way controller allows it to be “enabled” or “disabled.” Question – what is “Catch-in Focus”? --Thanks!



Last edited by Tom Lee; 06-29-2009 at 07:54 PM.
06-29-2009, 09:36 AM   #2
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QuoteOriginally posted by Tom Lee Quote
TQuestion – what is “Catch-in Focus”?

Thanks!
PDAF (phase detection auto focus) can tell you if something (some object - does not matter which one exactly) is in focus immediately (unlike CDAF), so "catch in focus" functionality can trigger the shutter if something (anything) will appear in the area where lens is focused...
06-29-2009, 09:14 PM   #3
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QuoteOriginally posted by Tom Lee Quote
Two K20D focus questions:

....... “The lens ID is displayed when obtained.” Question – how is it obtained? (Under Rec Mode, "Input Focal Length" is not active.)


2. In the camera Custom Menu screens, #34 is labeled “Catch-in Focus.” Clicking the four-way controller allows it to be “enabled” or “disabled.” Question – what is “Catch-in Focus”? --Thanks!
The ID of the mounted lens is obtained electronically via the lens chip.
The same way th Exif file will record what model of lens you used when you took the photo.
All Autofocus lenses should have this ID. It is based on the lens model e.g. a Pentax FA50mm f/1.4 or Tamron 17-50mm f/2.8 XR Di II , so if you mount a borrowed lens of the same model, the adjustment will apply because the camera won't know the difference.

"Catch-in-focus" refers to the Focus-Trap method you can use to have the Autofocus system trigger the shutter when using old manual-focus lenses. Its a very neat trick. The menu allows you to turn the capability off or on.
06-29-2009, 09:29 PM   #4
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Catch in focus is a function that, whan enabled, will trigger the shutter.
You will need either an old manual focus lens, or an AF lens on which you can disable the AF function.
The trick is you choose an AF point, adjust the focus to a value you choose by yourself (preset a distance), and press the shutter button. When the subject (think of somekind like wildlife or a racing car) is in focus, the camera will trigger the shutter. It's the same like taking pictures in low light, and the camera will be hunting and trigger the shot whan in focus.
This function is also usefull when you take sports photos. You wait the subject to come in focus rather then use AF.
Hope my answer is helpfull.

06-30-2009, 07:27 AM   #5
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Thank you for the reply. But dumb me needs some claification.

You say the ID is obtained electronically via the lens chip -- does this mean then that the adjustment of whatever lens is mounted at the time of adjustment will be retained, and applied each time said lens is affixed to the body?

I assume this is what happens, but just need to make certain, as there is no indication in the menu of this. Also, the menu line, "Input Focal Length" is grayed out, and I thought that might have something to do with it, but I guess not, as you might need to adjust different lenses of the same focal length.

Also, do you know what the increments are on the adjustment screen? They go from 1-10,. but 1-10 what? Inches, centimeters?

Sorry to come back to you with all this, but just wanted to be sure I understand it all. Thank you very much for your replies.

Tom



QuoteOriginally posted by kittykat46 Quote
The ID of the mounted lens is obtained electronically via the lens chip.
The same way th Exif file will record what model of lens you used when you took the photo.
All Autofocus lenses should have this ID. It is based on the lens model e.g. a Pentax FA50mm f/1.4 or Tamron 17-50mm f/2.8 XR Di II , so if you mount a borrowed lens of the same model, the adjustment will apply because the camera won't know the difference.

"Catch-in-focus" refers to the Focus-Trap method you can use to have the Autofocus system trigger the shutter when using old manual-focus lenses. Its a very neat trick. The menu allows you to turn the capability off or on.
06-30-2009, 08:16 PM   #6
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QuoteOriginally posted by Tom Lee Quote
- does this mean then that the adjustment of whatever lens is mounted at the time of adjustment will be retained, and applied each time said lens is affixed to the body?

Tom
That's correct - but the same lens model, even if its a different copy of it.
Unfortunately the User's Manual reads like a prescription but no clear explanation of what the function actually does.


QuoteOriginally posted by Tom Lee Quote
Also, do you know what the increments are on the adjustment screen? They go from 1-10,. but 1-10 what? Inches, centimeters?

Sorry to come back to you with all this, but just wanted to be sure I understand it all. Thank you very much for your replies.

Tom
As far as I can see, its an arbitrary scale.

+/- 1 hardly makes any visible difference, while +/- 10 is quite a visible change.

-negative adjustment is for Front Focus problems(the lens is focusing nearer than intended) +positive adjustment is for Back Focus - the lens is focusing further than intended).

Be Careful using this function. Use a focus test chart, set on a tripod, focus in good light. Controlled and repeatable conditions, a bit like a science experiment.

Many times what a user thinks is a Back or Front Focus problem is simply the camera focusing on a different object from what was intended - because its bigger, nearer, brighter, more contrasty etc. The centre focus is not really a small area, and if you have a mixture of near and far objects around it, its easy for the AF to get confused.

I hear the K-7 has improved on this - looking forward to it.
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