K20 catch focus with Tamron lens

FHPhotographer · 08-26-2009, 05:57 PM

I know the K20 can be set to catch (trap) focus with a manual lens, or with a Pentax lens with the AF/MF switch, but can it be made to work with a Tamron AF lens without the on-lens switch?
With my Pentax A50 MF lens, I switch the camera to AF, then manually focus until it catches and takes the shot, and frankly it's better than I can do by eye even with the KatzEye screen. And I'd like to figure out a setting on the K20 that would trap focus with my Tamron 28-75,
Brian

kittykat46 · 08-26-2009, 06:17 PM

On the Tamron 28-75mm it is not possible to do trap focus.
It is purely an auto focus lens when the camera's focus mode switch is set to auto focus.

A few Tamron lenses like the SP90 Macro have an on-lens manual focus switch, and you can do trap focus if you set that switch to manual + AF on the camera.

FHPhotographer · 08-27-2009, 10:39 AM

Originally posted by kittykat46

On the Tamron 28-75mm it is not possible to do trap focus.
It is purely an auto focus lens when the camera's focus mode switch is set to auto focus.

A few Tamron lenses like the SP90 Macro have an on-lens manual focus switch, and you can do trap focus if you set that switch to manual + AF on the camera.

That's what I thought, but I gave it a shot on the off chance somebody had a workaround. Thanks,
Brian

dlacouture · 08-27-2009, 02:14 PM

Actually, there is a (dirty) mean to do trap focus with a tamron 28-75 : just press the mount's locking button while composing... The AF motor will turn without actually driving the lens (as the AF shaft is retracted into the body), and the body will wait for AF confirm to take the pic...

Only problem : the motor will turn indefinitely...

octavmandru · 08-28-2009, 09:31 AM

Try to use some tape to insulate the lens contactsand use it as manual lens. Does your lens have aperture ring?

08-26-2009, 05:57 PM	#1
FHPhotographer Veteran Member Join Date: Jul 2008 Location: Fountain Hills, AZ Photos: Gallery \| Albums Posts: 1,297	K20 catch focus with Tamron lens I know the K20 can be set to catch (trap) focus with a manual lens, or with a Pentax lens with the AF/MF switch, but can it be made to work with a Tamron AF lens without the on-lens switch? With my Pentax A50 MF lens, I switch the camera to AF, then manually focus until it catches and takes the shot, and frankly it's better than I can do by eye even with the KatzEye screen. And I'd like to figure out a setting on the K20 that would trap focus with my Tamron 28-75, Brian

08-27-2009, 10:39 AM	#3
FHPhotographer Veteran Member Join Date: Jul 2008 Location: Fountain Hills, AZ Photos: Gallery \| Albums Posts: 1,297 Original Poster	That's what I thought Originally posted by kittykat46 On the Tamron 28-75mm it is not possible to do trap focus. It is purely an auto focus lens when the camera's focus mode switch is set to auto focus. A few Tamron lenses like the SP90 Macro have an on-lens manual focus switch, and you can do trap focus if you set that switch to manual + AF on the camera. That's what I thought, but I gave it a shot on the off chance somebody had a workaround. Thanks, Brian

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08-26-2009, 06:17 PM	#2
kittykat46 Veteran Member Join Date: Dec 2007 Posts: 923	On the Tamron 28-75mm it is not possible to do trap focus. It is purely an auto focus lens when the camera's focus mode switch is set to auto focus. A few Tamron lenses like the SP90 Macro have an on-lens manual focus switch, and you can do trap focus if you set that switch to manual + AF on the camera.

08-27-2009, 02:14 PM	#4
dlacouture Veteran Member Join Date: Jul 2008 Location: Var, South of France Photos: Albums Posts: 1,074	Actually, there is a (dirty) mean to do trap focus with a tamron 28-75 : just press the mount's locking button while composing... The AF motor will turn without actually driving the lens (as the AF shaft is retracted into the body), and the body will wait for AF confirm to take the pic... Only problem : the motor will turn indefinitely...

08-28-2009, 09:31 AM	#5
octavmandru Veteran Member Join Date: Jan 2009 Location: somewhere around Posts: 615	Try to use some tape to insulate the lens contactsand use it as manual lens. Does your lens have aperture ring?