Question on Pentax tele-converter and SDM lens.
Posted 11/06/2017 - 19:25
Link
The Pentax 1.7X is not designed to transfer the AF from the lens. It was originally designed so you could have Auto focus with a Manual lens.
I think the original instruction was to set the manual focus lens at infinity and let the 1.7x do the focusing for you. In practice I found you were better off getting the focus somewhere near and let the 1.7x do the fine tuning.
I think the original instruction was to set the manual focus lens at infinity and let the 1.7x do the focusing for you. In practice I found you were better off getting the focus somewhere near and let the 1.7x do the fine tuning.
Barrie - Too Old To Die Young
https://pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/
https://pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/
Posted 11/06/2017 - 21:11
Link
bforbes wrote:
The Pentax 1.7X is not designed to transfer the AF from the lens. It was originally designed so you could have Auto focus with a Manual lens.
I think the original instruction was to set the manual focus lens at infinity and let the 1.7x do the focusing for you. In practice I found you were better off getting the focus somewhere near and let the 1.7x do the fine tuning.
The Pentax 1.7X is not designed to transfer the AF from the lens. It was originally designed so you could have Auto focus with a Manual lens.
I think the original instruction was to set the manual focus lens at infinity and let the 1.7x do the focusing for you. In practice I found you were better off getting the focus somewhere near and let the 1.7x do the fine tuning.
Barrie is spot on. I use mine with MF and AF lenses regularly - you'll have to input the calculated focal length for the Shake Reduction system but once that's done exposure is calculated for you. These were taken with an F 100 Macro and the 1.7x AF converter the other day..


Excellent quality converter, highly recommended.
My spare will be available in a couple of weeks
LennyBloke
Posted 11/06/2017 - 22:24
Link
SDM will work with the HD Pentax-DA AF Rear Converter 1.4x AW and adjust the focal length as reported by the lens.
Alternatively the Kenko (and others) AF/Pz-AF 1.4x will also work with SDM lenses but it doesn't adjust the focal length.
The Pentax 1.7x converter is really an adapter for converting a manual focus lens into an AF lens and does it really well. It's strange mounting an early manual focus K lens and have it respond to a press of the shutter release or AF button. With an A series lens it all works just like having an AF lens attached.
Alternatively the Kenko (and others) AF/Pz-AF 1.4x will also work with SDM lenses but it doesn't adjust the focal length.
The Pentax 1.7x converter is really an adapter for converting a manual focus lens into an AF lens and does it really well. It's strange mounting an early manual focus K lens and have it respond to a press of the shutter release or AF button. With an A series lens it all works just like having an AF lens attached.
John K
Posted 12/06/2017 - 12:41
Link
JAK wrote:
SDM will work with the HD Pentax-DA AF Rear Converter 1.4x AW and adjust the focal length as reported by the lens.
Alternatively the Kenko (and others) AF/Pz-AF 1.4x will also work with SDM lenses but it doesn't adjust the focal length.
The Pentax 1.7x converter is really an adapter for converting a manual focus lens into an AF lens and does it really well. It's strange mounting an early manual focus K lens and have it respond to a press of the shutter release or AF button. With an A series lens it all works just like having an AF lens attached.
SDM will work with the HD Pentax-DA AF Rear Converter 1.4x AW and adjust the focal length as reported by the lens.
Alternatively the Kenko (and others) AF/Pz-AF 1.4x will also work with SDM lenses but it doesn't adjust the focal length.
The Pentax 1.7x converter is really an adapter for converting a manual focus lens into an AF lens and does it really well. It's strange mounting an early manual focus K lens and have it respond to a press of the shutter release or AF button. With an A series lens it all works just like having an AF lens attached.
The HD Pentax-DA AF Rear Converter is probably the best converter I've used on APS-C, but the designers weren't on the same page as the Full Frame team when they released it - it vignettes on the K1 with some lenses at least - I know they couldn't be expected to predict significant changes in future Pentax bodies but a FF model has been on the cards for a long time
Some of the Kenko/Teleplus/Tamron PZ versions do work with SDM (depending on the particular type/model) but on the whole tend to be not quite as consistent as the Pentax HD model. There are many reports of focus hunting with some combinations, even when the lens has a relatively fast aperture.
LennyBloke
Add Comment
To leave a comment - Log in to Pentax User or create a new account.
1 posts
7 years
I have seen a tele-extender by Pentax: smc Pentax-F 1.7X AF adapter. it is not clear if it will convey the focusing information from camera to lens or if I will lose the auto-focus feature. Any information is welcome.