Question about AF motor

thekylestyle · 10-19-2016, 10:44 PM

Hey guys,

Got the Samyang 14mm (K mount) today, for use with my K1. This lens is a manual focus only lens, but I thought that'd be all good because my K1 has an in body focus motor.

Thing is, how on earth do we turn the focus motor on??? Any help would be amazing.

First post on the forums by the way

- Kyle

Bengan · 10-19-2016, 10:53 PM

You misunderstood the internal focus motor function. Manual focus lenses means using your hand to turn the focus ring. The internal screw drive motor works with auto focus lenses that don't have built-in focus motors.

Giklab · 10-19-2016, 11:39 PM

What Bengan said. The good news is that it's not a total loss, it's a very good lens and manual focus is quite easy with wider lenses. And if you use live view, there's focus peaking to help

**UncleVanya** · 10-20-2016, 07:36 AM

There are three types of autofocus lenses. The oldest style is self contained, focus system and motors and all. There are some rare adaptall versions of this as I understand. Pentax made a single lens of this type years ago. The next oldest designs use a camera body motor commonly called screw drive. It essentially is able to interface with a lens designed for this and rotate a slotted head on the body to move the interface on the lens allowing the lens to focus. Next up are the type of lenses with built in motors. These generally have nearly silent motors. Some are focus by wire (no directly manipulated mechanical interface to the optics. )

This is an oversimplification but it covers the basics.

Manual lenses are manual focus. The only exception on Pentax is when using the F series autofocus adapter. This acts as a 1.7x multiplier and allows a limited type of autofocus by using screw drive to shift elements inside of inself. The loss of 1.5 stops makes this most practical with fast telephoto lenses.

10-19-2016, 10:44 PM	#1
thekylestyle New Member Join Date: Oct 2016 Posts: 1	Question about AF motor Hey guys, Got the Samyang 14mm (K mount) today, for use with my K1. This lens is a manual focus only lens, but I thought that'd be all good because my K1 has an in body focus motor. Thing is, how on earth do we turn the focus motor on??? Any help would be amazing. First post on the forums by the way - Kyle

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10-19-2016, 10:53 PM	#2
Bengan Pentaxian Join Date: Nov 2012 Location: Stockholm Photos: Gallery \| Albums Posts: 1,756	You misunderstood the internal focus motor function. Manual focus lenses means using your hand to turn the focus ring. The internal screw drive motor works with auto focus lenses that don't have built-in focus motors.

10-19-2016, 11:39 PM	#3
Giklab Veteran Member Join Date: Jan 2012 Location: Slovenia Photos: Gallery Posts: 2,182	What Bengan said. The good news is that it's not a total loss, it's a very good lens and manual focus is quite easy with wider lenses. And if you use live view, there's focus peaking to help

10-20-2016, 07:36 AM	#4
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,406	There are three types of autofocus lenses. The oldest style is self contained, focus system and motors and all. There are some rare adaptall versions of this as I understand. Pentax made a single lens of this type years ago. The next oldest designs use a camera body motor commonly called screw drive. It essentially is able to interface with a lens designed for this and rotate a slotted head on the body to move the interface on the lens allowing the lens to focus. Next up are the type of lenses with built in motors. These generally have nearly silent motors. Some are focus by wire (no directly manipulated mechanical interface to the optics. ) This is an oversimplification but it covers the basics. Manual lenses are manual focus. The only exception on Pentax is when using the F series autofocus adapter. This acts as a 1.7x multiplier and allows a limited type of autofocus by using screw drive to shift elements inside of inself. The loss of 1.5 stops makes this most practical with fast telephoto lenses.