Auto focus issue k100d

jbrennskag · 09-04-2020, 11:17 AM

I am a total newbie to pentax digital slr's. I just purchased a used k100d..I know its old only 6.1 mp...and I am excited to try it out. I have mounted a pentax dfa 28-105 lens. The af/mf switch i have set to af (several times) but the viewfinder shows 'MF' and the lens will not autofocus. In the menu the focus mode is set to af-s. Am I missing something?

Joe

**jatrax** · 09-04-2020, 11:46 AM

Unfortunately that lens will not auto-focus with that camera. The lens has an in-lens AF motor and does not have screw-drive capability. Lens has a KAF3 mount. It should work fine with the K100D, except no auto-focus.

---------- Post added 09-04-20 at 11:47 AM ----------

There are a large number of other lenses that will work though. In fact the majority of Pentax lenses will work. it is only the very newest ones that might have issues.

---------- Post added 09-04-20 at 11:49 AM ----------

Here are the specs for that camera: Pentax K100D - Pentax K-mount DSLRs - Pentax Camera Reviews and Specifications
Check the lens mount section.

jbrennskag · 09-04-2020, 11:50 AM

Thanks. I have taken several shots using manual focusing and that works fine. So I have to look for a lens with screw-drive focus?

Joe

**jatrax** · 09-04-2020, 11:51 AM

I am curious, how did you end up with a very new DFA lens and a 13 year old camera?

---------- Post added 09-04-20 at 11:53 AM ----------

Originally posted by jbrennskag

So I have to look for a lens with screw-drive focus?

That is correct. Which is nearly all Pentax lenses. Just avoid those with KAF3 or KAF4 mounts. Anything in the Pentax-F or Pentax-FA series will work. And I think all Pentax-DA lenses will but I'm not 100% on that.

stevebrot · 09-04-2020, 11:54 AM

Originally posted by jbrennskag

I am a total newbie to pentax digital slr's. I just purchased a used k100d..I know its old only 6.1 mp...and I am excited to try it out. I have mounted a pentax dfa 28-105 lens. The af/mf switch i have set to af (several times) but the viewfinder shows 'MF' and the lens will not autofocus. In the menu the focus mode is set to af-s. Am I missing something?

Joe

Sadly, your K100D is limited to lenses that use the mechanical drive on the body for autofocus. The D FA 28-105 has an in-lens focus motor and no coupling for the mechanical drive.

Steve

swanlefitte · 09-04-2020, 11:55 AM

The lens is the newer kaf3. Here is the forums compatability. Pentax K110D and HD Pentax-D FA 28-105mm F3.5-5.6 ED DC WR - Compatibility | PentaxForums.com
The camera will only manualy focus the lens because it lacks the electric contacts. If you look inside the k100d just inside the bottom, it is round on the left but on the right it has a shape in there. That is where the electric contacts would be. You can see the lens has contacts there.

**jatrax** · 09-04-2020, 11:56 AM

Check here for compatibility before you buy: Pentax Lenses - Pentax Lens Reviews & Lens Database

Note that all Pentax-K, Pentax-M and Pentax-A lenses will also work but they do not have any auto-focus as they are pre-autofocus lenses.

**aslyfox** · 09-04-2020, 11:59 AM

theser charts may be helpful:

Quote:

Pentax K-mount Lens Compatibility Chart
Copyright 2006-2020 Mosphotos.com. All rights reserved.

Pentax bayonet lenses labeled "SMC Pentax" are referred to as "K" lenses in the table below. Other Pentax bayonet lenses have the lens designation as a part of their name as in "SMC Pentax-FA".
Note that "star" lenses work like their "non-star" counterparts unless they are singled out in the table below. So for compatibility of a DA* lens which is not singled out, look under DA lenses, etc.
Exceptions:
FA and F "soft" lenses behave like M lenses in terms of metering.

Check this page out for more on the Pentax lens nomenclature: Pentax lens series explained.

The Pentax K-mount Camera Lens Compatibility Chart

Quote:

Pentax K-Mount Lens Series Explained: The differences between various Pentax lens series

In a nutshell
There are several series of Pentax K-mount lenses; the ones currently being produced include the DA (digital), DA L (cheap digital kit), D FA (full-frame, digital optimized), and FA (full-frame) series. While all Pentax K-mount lenses ever produced are compatible with all current Pentax DSLRs (in some cases with restrictions in that not all exposure modes of the camera are supported by old lenses), there are significant differences between each lens series and each has different features. Furthermore some of the newer lenses do not work with older cameras. We'll be exploring the differences between the various K-mount series lenses in this article. Read more about specific K-mount lens/camera compatibility here.
The DLSR designation below encompasses the mirror-less K-01

Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

**mikesbike** · 09-04-2020, 12:06 PM

Originally posted by jatrax

am curious, how did you end up with a very new DFA lens and a 13 year old camera?

Me too, it is a mis-match in more ways than even the lack of AF capability. The D-FA lenses are designed for Full Frame (FF) bodies and tend to be more expensive, larger, and heavier than a lens of similar capability designed for APS-C use. The D-FA 28-105 will have a good zoom range on a FF body, like a K-1, but will totally lack any wide angle capability on an APS-C body.

As to the Pentax K100D, it does not have the contacts for using lenses having their own AF motors, which are many. It will work fine for AF with lenses designed to work with the old basic screw-driven system, which also are many. The little kit lens, DA 18-55mm will work fine with it, and is inexpensive. It came in several versions. The newest small kit lens, the DA 18-50mm will not. The K100D Super is the same camera essentially with those contacts added. After having used this camera for quite some time, I found the K200D to be far better. It does tend to under-expose very slightly, which is easy to compensate for when needed, but it offers better resolution, has a much better build quality, including Weather-Resistant (WR) construction, and more advanced control systems. It will AF fine with lenses having their own motors or ones of screw-driven design.

In the case of Nikon, for example, at one point they switched their entry-level DSLRs so they will ONLY AF with lenses having their own motors, and will not AF with any of their lenses designed for screw-driven use- which are many and some being very good lenses! And if shopping for a body having WR construction, in their brand you'd be looking in the $1,000+ USD range for a new camera, and used bodies of this caliber are not cheap either.

**Sakura** · 09-04-2020, 03:17 PM

But the bottom line, the K100D is a very nice camera, it was my first digital Pentax camera and at that time i was very pleased with it.

**UncleVanya** · 09-04-2020, 04:19 PM

K100d super will focus that lens but not the k100d as people have mentioned.

jbrennskag · 09-04-2020, 04:37 PM - **2 Likes**

Thank you all so much for jumping in. I also had a Pentax FA 31mm stashed away and I tried that and the autofocus worked fine. Now the backstory of how I had the 28-105 DFA lens. I purchased a K1 Mii and bought several lenses for that camera. Due to health issues, I have not been able to use it yet or try it out but that time is coming shortly.

I purchased the k100d on a whim last week, because of the CCD sensor. I don't know why I am so excited about that camera. My first digital SLR, now long gone, was a Nikon D100 and it had a CCD sensor. I always liked the images from the D100. It seems like the K100d is built much better than the d100. For my purposes, the k100d is just for enjoyment, it was less than $100, and seems to produce excellent images. I've always been a bit mystified about Pentax lens compatibility, but I thank you all for clearing that up.

Joe

swanlefitte · 09-04-2020, 04:51 PM

It is interesting that the k100 has the shape for the contacts with a plug in place of the contacts. Kaf3 must have been in r&d at the time but not quite ready when the k100d rolled out. If I take the plug out, I wonder how much kaf3 hardware is inside. Will try to get a photo up of the plug later. Typing while cooking now, then a bike ride.

**mikesbike** · 09-05-2020, 04:15 PM

A K-1 II wth the DFA 28-105mm, now that makes perfect sense. With the FA 31mm f/1.8 Limited? Wow- you've got plenty to look forward to!

Ivan · 09-06-2020, 03:47 AM

Originally posted by jbrennskag

Thank you all so much for jumping in. I also had a Pentax FA 31mm stashed away and I tried that and the autofocus worked fine. Now the backstory of how I had the 28-105 DFA lens. I purchased a K1 Mii and bought several lenses for that camera. Due to health issues, I have not been able to use it yet or try it out but that time is coming shortly.

I purchased the k100d on a whim last week, because of the CCD sensor. I don't know why I am so excited about that camera. My first digital SLR, now long gone, was a Nikon D100 and it had a CCD sensor. I always liked the images from the D100. It seems like the K100d is built much better than the d100. For my purposes, the k100d is just for enjoyment, it was less than $100, and seems to produce excellent images. I've always been a bit mystified about Pentax lens compatibility, but I thank you all for clearing that up.

Joe

A speedy recovery. But Nikon D100 seemed more convenient to me. I really lack buttons and levers in Pentax 100d)).

09-04-2020, 11:17 AM	#1
jbrennskag New Member Join Date: May 2019 Photos: Albums Posts: 22	Auto focus issue k100d I am a total newbie to pentax digital slr's. I just purchased a used k100d..I know its old only 6.1 mp...and I am excited to try it out. I have mounted a pentax dfa 28-105 lens. The af/mf switch i have set to af (several times) but the viewfinder shows 'MF' and the lens will not autofocus. In the menu the focus mode is set to af-s. Am I missing something? Joe

09-04-2020, 12:06 PM	#9
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,549	Originally posted by jatrax am curious, how did you end up with a very new DFA lens and a 13 year old camera? Me too, it is a mis-match in more ways than even the lack of AF capability. The D-FA lenses are designed for Full Frame (FF) bodies and tend to be more expensive, larger, and heavier than a lens of similar capability designed for APS-C use. The D-FA 28-105 will have a good zoom range on a FF body, like a K-1, but will totally lack any wide angle capability on an APS-C body. As to the Pentax K100D, it does not have the contacts for using lenses having their own AF motors, which are many. It will work fine for AF with lenses designed to work with the old basic screw-driven system, which also are many. The little kit lens, DA 18-55mm will work fine with it, and is inexpensive. It came in several versions. The newest small kit lens, the DA 18-50mm will not. The K100D Super is the same camera essentially with those contacts added. After having used this camera for quite some time, I found the K200D to be far better. It does tend to under-expose very slightly, which is easy to compensate for when needed, but it offers better resolution, has a much better build quality, including Weather-Resistant (WR) construction, and more advanced control systems. It will AF fine with lenses having their own motors or ones of screw-driven design. In the case of Nikon, for example, at one point they switched their entry-level DSLRs so they will ONLY AF with lenses having their own motors, and will not AF with any of their lenses designed for screw-driven use- which are many and some being very good lenses! And if shopping for a body having WR construction, in their brand you'd be looking in the $1,000+ USD range for a new camera, and used bodies of this caliber are not cheap either. Last edited by mikesbike; 09-04-2020 at 12:44 PM.

09-04-2020, 04:37 PM - 2 Likes	#12
jbrennskag New Member Join Date: May 2019 Photos: Albums Posts: 22 Original Poster	Auto Focus Issue K100d Thank you all so much for jumping in. I also had a Pentax FA 31mm stashed away and I tried that and the autofocus worked fine. Now the backstory of how I had the 28-105 DFA lens. I purchased a K1 Mii and bought several lenses for that camera. Due to health issues, I have not been able to use it yet or try it out but that time is coming shortly. I purchased the k100d on a whim last week, because of the CCD sensor. I don't know why I am so excited about that camera. My first digital SLR, now long gone, was a Nikon D100 and it had a CCD sensor. I always liked the images from the D100. It seems like the K100d is built much better than the d100. For my purposes, the k100d is just for enjoyment, it was less than $100, and seems to produce excellent images. I've always been a bit mystified about Pentax lens compatibility, but I thank you all for clearing that up. Joe

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09-04-2020, 11:46 AM	#2
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Unfortunately that lens will not auto-focus with that camera. The lens has an in-lens AF motor and does not have screw-drive capability. Lens has a KAF3 mount. It should work fine with the K100D, except no auto-focus. ---------- Post added 09-04-20 at 11:47 AM ---------- There are a large number of other lenses that will work though. In fact the majority of Pentax lenses will work. it is only the very newest ones that might have issues. ---------- Post added 09-04-20 at 11:49 AM ---------- Here are the specs for that camera: Pentax K100D - Pentax K-mount DSLRs - Pentax Camera Reviews and Specifications Check the lens mount section.

09-04-2020, 11:50 AM	#3
jbrennskag New Member Join Date: May 2019 Photos: Albums Posts: 22 Original Poster	Thanks. I have taken several shots using manual focusing and that works fine. So I have to look for a lens with screw-drive focus? Joe

09-04-2020, 11:51 AM	#4
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	I am curious, how did you end up with a very new DFA lens and a 13 year old camera? ---------- Post added 09-04-20 at 11:53 AM ---------- Originally posted by jbrennskag So I have to look for a lens with screw-drive focus? That is correct. Which is nearly all Pentax lenses. Just avoid those with KAF3 or KAF4 mounts. Anything in the Pentax-F or Pentax-FA series will work. And I think all Pentax-DA lenses will but I'm not 100% on that.

09-04-2020, 11:54 AM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by jbrennskag I am a total newbie to pentax digital slr's. I just purchased a used k100d..I know its old only 6.1 mp...and I am excited to try it out. I have mounted a pentax dfa 28-105 lens. The af/mf switch i have set to af (several times) but the viewfinder shows 'MF' and the lens will not autofocus. In the menu the focus mode is set to af-s. Am I missing something? Joe Sadly, your K100D is limited to lenses that use the mechanical drive on the body for autofocus. The D FA 28-105 has an in-lens focus motor and no coupling for the mechanical drive. Steve

09-04-2020, 11:55 AM	#6
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	The lens is the newer kaf3. Here is the forums compatability. Pentax K110D and HD Pentax-D FA 28-105mm F3.5-5.6 ED DC WR - Compatibility \| PentaxForums.com The camera will only manualy focus the lens because it lacks the electric contacts. If you look inside the k100d just inside the bottom, it is round on the left but on the right it has a shape in there. That is where the electric contacts would be. You can see the lens has contacts there.

09-04-2020, 11:56 AM	#7
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Check here for compatibility before you buy: Pentax Lenses - Pentax Lens Reviews & Lens Database Note that all Pentax-K, Pentax-M and Pentax-A lenses will also work but they do not have any auto-focus as they are pre-autofocus lenses.

09-04-2020, 11:59 AM	#8
aslyfox Seeker of Knowledge Join Date: Aug 2016 Location: Topeka, Kansas Photos: Gallery \| Albums Posts: 24,581	theser charts may be helpful: Quote: Pentax K-mount Lens Compatibility Chart Copyright 2006-2020 Mosphotos.com. All rights reserved. Pentax bayonet lenses labeled "SMC Pentax" are referred to as "K" lenses in the table below. Other Pentax bayonet lenses have the lens designation as a part of their name as in "SMC Pentax-FA". Note that "star" lenses work like their "non-star" counterparts unless they are singled out in the table below. So for compatibility of a DA* lens which is not singled out, look under DA lenses, etc. Exceptions: FA and F "soft" lenses behave like M lenses in terms of metering. Check this page out for more on the Pentax lens nomenclature: Pentax lens series explained. The Pentax K-mount Camera Lens Compatibility Chart Quote: Pentax K-Mount Lens Series Explained: The differences between various Pentax lens series In a nutshell There are several series of Pentax K-mount lenses; the ones currently being produced include the DA (digital), DA L (cheap digital kit), D FA (full-frame, digital optimized), and FA (full-frame) series. While all Pentax K-mount lenses ever produced are compatible with all current Pentax DSLRs (in some cases with restrictions in that not all exposure modes of the camera are supported by old lenses), there are significant differences between each lens series and each has different features. Furthermore some of the newer lenses do not work with older cameras. We'll be exploring the differences between the various K-mount series lenses in this article. Read more about specific K-mount lens/camera compatibility here. The DLSR designation below encompasses the mirror-less K-01 Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

09-04-2020, 03:17 PM	#10
Sakura Site Supporter Join Date: Jan 2010 Location: Netherlands Photos: Gallery Posts: 438	But the bottom line, the K100D is a very nice camera, it was my first digital Pentax camera and at that time i was very pleased with it.

09-04-2020, 04:19 PM	#11
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	K100d super will focus that lens but not the k100d as people have mentioned.

09-04-2020, 04:51 PM	#13
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	It is interesting that the k100 has the shape for the contacts with a plug in place of the contacts. Kaf3 must have been in r&d at the time but not quite ready when the k100d rolled out. If I take the plug out, I wonder how much kaf3 hardware is inside. Will try to get a photo up of the plug later. Typing while cooking now, then a bike ride.

09-05-2020, 04:15 PM	#14
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,549	A K-1 II wth the DFA 28-105mm, now that makes perfect sense. With the FA 31mm f/1.8 Limited? Wow- you've got plenty to look forward to!

09-06-2020, 03:47 AM	#15
Ivan Pentaxian Join Date: Dec 2019 Location: Moscow Posts: 639	Originally posted by jbrennskag Thank you all so much for jumping in. I also had a Pentax FA 31mm stashed away and I tried that and the autofocus worked fine. Now the backstory of how I had the 28-105 DFA lens. I purchased a K1 Mii and bought several lenses for that camera. Due to health issues, I have not been able to use it yet or try it out but that time is coming shortly. I purchased the k100d on a whim last week, because of the CCD sensor. I don't know why I am so excited about that camera. My first digital SLR, now long gone, was a Nikon D100 and it had a CCD sensor. I always liked the images from the D100. It seems like the K100d is built much better than the d100. For my purposes, the k100d is just for enjoyment, it was less than $100, and seems to produce excellent images. I've always been a bit mystified about Pentax lens compatibility, but I thank you all for clearing that up. Joe A speedy recovery. But Nikon D100 seemed more convenient to me. I really lack buttons and levers in Pentax 100d)).