Hi there. Screw drive vs PLM pulse.

**MichaelS** · 06-17-2017, 06:07 PM

Hello to you all. Bear with me this is my first thread so hear goes. I'm looking to upgrade from an older Tamron 70/300mm for my K5 and I'm looking at two Pentax options. One is described as pulse AF (PLM) and the other is described as Screw drive AF. How does Pulse work and is it compatible with a K5?

**patrick9** · 06-17-2017, 06:13 PM

Hello Michael welcome to the Forums. I can not help on your question but there are others her that can. So I will let one of them field the question.

**jatrax** · 06-17-2017, 06:26 PM

Welcome, Michael!
Screwdrive = focusing elements are driven by a motor in the camera though a mechanical connection. This system is rock solid, proven over decades. However, it can be noisy depending on the lens and focusing speed is restricted to the motor speed. All Pentax AF cameras use this system so compatibility is assured.

PLM = focusing elements are driven by a motor in the lens itself. This was introduced with the KAF4 mount. According to Ricoh it is compatible with the k-3 and newer. I believe it was not compatible with the k-3 at launch and a firmware update added that. Cameras listed as compatible are: K-3, K-3 II, K-50, K-70, K-S1, K-S2, KP and K-1.

So unless something is changed with a firmware update (unlikely at this point) your K-5 will not work with PLM lenses. It most certainly will work with any screwdrive lens.

**MichaelS** · 06-17-2017, 06:34 PM

Originally posted by jatrax

Welcome, Michael!
Screwdrive = focusing elements are driven by a motor in the camera though a mechanical connection. This system is rock solid, proven over decades. However, it can be noisy depending on the lens and focusing speed is restricted to the motor speed. All Pentax AF cameras use this system so compatibility is assured.

PLM = focusing elements are driven by a motor in the lens itself. This was introduced with the KAF4 mount. According to Ricoh it is compatible with the k-3 and newer. I believe it was not compatible with the k-3 at launch and a firmware update added that. Cameras listed as compatible are: K-3, K-3 II, K-50, K-70, K-S1, K-S2, KP and K-1.

So unless something is changed with a firmware update (unlikely at this point) your K-5 will not work with PLM lenses. It most certainly will work with any screwdrive lens.

Wow, that was quick and helps with my decision. (Saved some money too I think.) First experience with the forum was a hit. thanks Patrick9 and jatrax.

**jatrax** · 06-17-2017, 08:00 PM

It appears from your post you are looking at the Pentax 55-300. This lens comes in a number of different versions although the optics appear to be identical. This forum maintains a lens database, look at the top under "lenses". Here is a link to the page with the DA 55-300: Pentax DA Zoom Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database

The original version DA 55-300 F/4-5.8 ED also came in a DA L version. This was sold only as part of multi-lens 'kits' but is widely available second hand. If budget is a priority you might take a look at the DA L version, optically identical to the DA version but does not have quick-shift or a hood. The DA 55-300 F/4-5.8 ED WR version was introduced in 2013 I think and includes weather sealing. The new DA 55-300 F/4-5.8 ED PLM WR RE version was recently introduced and is the first version with an in-lens AF motor. I have not seen an optic diagram of this lens but it is likely (but I do not know) that the optics are different in this version to accommodate the PLM motor. It does get good reviews, but unfortunately is not backwards compatible.

Adam · 06-17-2017, 09:57 PM

Originally posted by MichaelS

Hello to you all. Bear with me this is my first thread so hear goes. I'm looking to upgrade from an older Tamron 70/300mm for my K5 and I'm looking at two Pentax options. One is described as pulse AF (PLM) and the other is described as Screw drive AF. How does Pulse work and is it compatible with a K5?

PLM autofocus doesn't work on the K-5. It is however MUCH faster to focus than any other Pentax lens, even those with DC silent focus. If you plan to upgrade your body to a K-3 or newer eventually, the 55-300mm PLM is the way to go.

**Kerrowdown** · 06-18-2017, 12:47 AM

I'll just say welcome, as all these knowledge folk here have already answered your question.

C_Jones · 06-18-2017, 07:52 AM

Welcome to the forums.

normhead · 06-18-2017, 09:20 AM

Welcome to the forum.

Cthulhugan · 06-18-2017, 09:50 AM

Originally posted by Adam

PLM autofocus doesn't work on the K-5. It is however MUCH faster to focus than any other Pentax lens, even those with DC silent focus. If you plan to upgrade your body to a K-3 or newer eventually, the 55-300mm PLM is the way to go.

IIRC the 55-300 PLM has the new KAF4 electronic aperture, which won't work at all on a K-5, not even as manual focus.

Adam · 06-18-2017, 04:10 PM

Originally posted by Cthulhugan

IIRC the 55-300 PLM has the new KAF4 electronic aperture, which won't work at all on a K-5, not even as manual focus.

Correct, it will always shoot wide-open. Manual focusing should work, though.

06-17-2017, 06:07 PM	#1
MichaelS Loyal Site Supporter Join Date: Jun 2017 Location: Columbus, Ohio USA Posts: 50	Hi there. Screw drive vs PLM pulse. Hello to you all. Bear with me this is my first thread so hear goes. I'm looking to upgrade from an older Tamron 70/300mm for my K5 and I'm looking at two Pentax options. One is described as pulse AF (PLM) and the other is described as Screw drive AF. How does Pulse work and is it compatible with a K5?

06-17-2017, 09:57 PM	#6
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Originally posted by MichaelS Hello to you all. Bear with me this is my first thread so hear goes. I'm looking to upgrade from an older Tamron 70/300mm for my K5 and I'm looking at two Pentax options. One is described as pulse AF (PLM) and the other is described as Screw drive AF. How does Pulse work and is it compatible with a K5? PLM autofocus doesn't work on the K-5. It is however MUCH faster to focus than any other Pentax lens, even those with DC silent focus. If you plan to upgrade your body to a K-3 or newer eventually, the 55-300mm PLM is the way to go. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-18-2017, 04:10 PM	#11
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Originally posted by Cthulhugan IIRC the 55-300 PLM has the new KAF4 electronic aperture, which won't work at all on a K-5, not even as manual focus. Correct, it will always shoot wide-open. Manual focusing should work, though. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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06-17-2017, 06:13 PM	#2
patrick9 Site Supporter Join Date: Feb 2011 Location: Murfreesboro Tennessee Photos: Gallery \| Albums Posts: 3,458	Hello Michael welcome to the Forums. I can not help on your question but there are others her that can. So I will let one of them field the question.

06-17-2017, 06:26 PM	#3
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Welcome, Michael! Screwdrive = focusing elements are driven by a motor in the camera though a mechanical connection. This system is rock solid, proven over decades. However, it can be noisy depending on the lens and focusing speed is restricted to the motor speed. All Pentax AF cameras use this system so compatibility is assured. PLM = focusing elements are driven by a motor in the lens itself. This was introduced with the KAF4 mount. According to Ricoh it is compatible with the k-3 and newer. I believe it was not compatible with the k-3 at launch and a firmware update added that. Cameras listed as compatible are: K-3, K-3 II, K-50, K-70, K-S1, K-S2, KP and K-1. So unless something is changed with a firmware update (unlikely at this point) your K-5 will not work with PLM lenses. It most certainly will work with any screwdrive lens.

06-17-2017, 06:34 PM	#4
MichaelS Loyal Site Supporter Join Date: Jun 2017 Location: Columbus, Ohio USA Posts: 50 Original Poster	Originally posted by jatrax Welcome, Michael! Screwdrive = focusing elements are driven by a motor in the camera though a mechanical connection. This system is rock solid, proven over decades. However, it can be noisy depending on the lens and focusing speed is restricted to the motor speed. All Pentax AF cameras use this system so compatibility is assured. PLM = focusing elements are driven by a motor in the lens itself. This was introduced with the KAF4 mount. According to Ricoh it is compatible with the k-3 and newer. I believe it was not compatible with the k-3 at launch and a firmware update added that. Cameras listed as compatible are: K-3, K-3 II, K-50, K-70, K-S1, K-S2, KP and K-1. So unless something is changed with a firmware update (unlikely at this point) your K-5 will not work with PLM lenses. It most certainly will work with any screwdrive lens. Wow, that was quick and helps with my decision. (Saved some money too I think.) First experience with the forum was a hit. thanks Patrick9 and jatrax.

06-17-2017, 08:00 PM	#5
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	It appears from your post you are looking at the Pentax 55-300. This lens comes in a number of different versions although the optics appear to be identical. This forum maintains a lens database, look at the top under "lenses". Here is a link to the page with the DA 55-300: Pentax DA Zoom Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database The original version DA 55-300 F/4-5.8 ED also came in a DA L version. This was sold only as part of multi-lens 'kits' but is widely available second hand. If budget is a priority you might take a look at the DA L version, optically identical to the DA version but does not have quick-shift or a hood. The DA 55-300 F/4-5.8 ED WR version was introduced in 2013 I think and includes weather sealing. The new DA 55-300 F/4-5.8 ED PLM WR RE version was recently introduced and is the first version with an in-lens AF motor. I have not seen an optic diagram of this lens but it is likely (but I do not know) that the optics are different in this version to accommodate the PLM motor. It does get good reviews, but unfortunately is not backwards compatible.

06-18-2017, 12:47 AM	#7
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,819	I'll just say welcome, as all these knowledge folk here have already answered your question.

06-18-2017, 07:52 AM	#8
C_Jones Pentaxian Join Date: Sep 2012 Location: NY Photos: Gallery \| Albums Posts: 6,084	Welcome to the forums.

06-18-2017, 09:20 AM	#9
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Welcome to the forum.

06-18-2017, 09:50 AM	#10
Cthulhugan Senior Member Join Date: Dec 2015 Location: Calgary Alberta Canada Photos: Gallery Posts: 227	Originally posted by Adam PLM autofocus doesn't work on the K-5. It is however MUCH faster to focus than any other Pentax lens, even those with DC silent focus. If you plan to upgrade your body to a K-3 or newer eventually, the 55-300mm PLM is the way to go. IIRC the 55-300 PLM has the new KAF4 electronic aperture, which won't work at all on a K-5, not even as manual focus.