DA 35mm 2.4 Focus Problem

raderstudios · 05-12-2021, 01:31 PM

Hi all,

I recently picked up a second-hand DA 35mm 2.4, and unfortunately it seems to be damaged. The autofocus doesn't function at all - no noise or attempt from the body to focus the lens. I have tried the lens on a K20D and a K100, verified that both are in AF mode, cleaned the contacts on both bodies and the lens. Nothing. Also, with the bodies in MF, I have tried focusing manually. The lens will focus optically, but the cameras do not detect focus, won't signal focus, and will not trigger the shutter release. Is there a way to fix this, or is the poor little Plastic Fantastic a goner?

Thanks in advance or your help!

Bertrand3000 · 05-12-2021, 01:38 PM

This lens should work on your K100D and K20D. Is the camera displaying F-- in the viewfinder? That would mean the electronic part is dead somehow, or contacts not effective but you already cleaned them... Can you share a picture of the back of the poor lens, so I can compare it with my (functional) DA 35 F2.4?

If F-- is displayed, I suppose you could try to take shots in MF though, but you will have to enable "Use Aperture Ring" in the setup. This is to allow K and M lenses to work ; it should allow you to shoot the DA 35 as well, but only wide open though, due to lack of aperture ring.

raderstudios · 05-12-2021, 02:02 PM

Thanks for your help! The viewfinder is displaying normally on both cameras. Here's an image (I cheated and used my Pixel phone - I know I'll have to be drawn and quartered now

)

stevebrot · 05-12-2021, 02:07 PM

If the camera does not attempt to focus, it generally means that an AF lens has not been detected through the data pin (contact furthest from the lens retention pin) on the camera. That can happen if the matchning contact on the lens is non-functional or the internal electronics that do the communication are bad.

Steve

stevebrot · 05-12-2021, 02:08 PM

If the camera does not attempt to focus, it generally means that an AF lens has not been detected through the data pin (contact furthest from the lens retention pin) on the camera. That can happen if the matching contact on the lens is non-functional or the internal lens electronics that do the communication are bad.

Steve

Bertrand3000 · 05-12-2021, 02:22 PM

Okay. Looks clean enough. If you manually turn the focus ring, will the screw at the back of the lens turn? It definitely should.

raderstudios · 05-12-2021, 02:23 PM

Originally posted by Bertrand3000

Okay. Looks clean enough. If you manually turn the focus ring, will the screw at the back of the lens turn? It definitely should.

Yes it does.

Bertrand3000 · 05-12-2021, 02:30 PM

That means that mechanically your lens is fine. If you don't get F-- then the electronic part cannot be fried either. I am at a loss of what is happening here.

If you put your camera in aperture priority mode, then stop down to let's say F5.6 and try optical preview, will the aperture close a bit?

**Belnan** · 05-12-2021, 02:49 PM

That sucks. Sorry not helpful.

Kendra59 · 05-12-2021, 02:50 PM

Try gently rubbing the electronic contacts with a clean pencil eraser... This often works with other electronics.

**ramseybuckeye** · 05-12-2021, 03:11 PM

If cleaning the contacts does not work, get a refund.

**Bob 256** · 05-12-2021, 03:36 PM

This might be a dumb question but.......... is your camera in manual or autofocus mode? If it's in manual, autofocus isn't going to do anything but the camera should still detect the focus point and alert you when good focus is manually achieved (it should be working like a generic manual focus lens). Just want to be sure that little switch in in the "autofocus" position.

raderstudios · 05-12-2021, 03:44 PM

Originally posted by Bertrand3000

That means that mechanically your lens is fine. If you don't get F-- then the electronic part cannot be fried either. I am at a loss of what is happening here.

If you put your camera in aperture priority mode, then stop down to let's say F5.6 and try optical preview, will the aperture close a bit?

Oh, this highlighted another symptom. The camera won't enter optical preview mode with the lens attached.

---------- Post added 05-12-21 at 03:46 PM ----------

Originally posted by Bob 256

This might be a dumb question but.......... is your camera in manual or autofocus mode? If it's in manual, autofocus isn't going to do anything but the camera should still detect the focus point and alert you when good focus is manually achieved (it should be working like a generic manual focus lens). Just want to be sure that little switch in in the "autofocus" position.

Yep, definitely in AF mode. I have played with it in MF mode, too, and the camera will not detect focus, even when the scene is visibly in focus.

---------- Post added 05-12-21 at 03:51 PM ----------

Originally posted by ramseybuckeye

If cleaning the contacts does not work, get a refund.

That does seem to be the way this is heading...

stevebrot · 05-12-2021, 04:46 PM

Originally posted by Bertrand3000

That means that mechanically your lens is fine. If you don't get F-- then the electronic part cannot be fried either. I am at a loss of what is happening here.

While the "A" contact "gates" both aperture control, all it means is that the mount contacts are not evaluated unless the "A" contact is detected. Evaluation of the contacts will result in aperture control (no F--) enabled at minimum, but is no guarantee that AF is also functional.

I am pretty sure that most (all?) Pentax lenses having no aperture ring have the "A" contact hard-wired as "present/on". I can't say for sure for the DA 35/2.4, but as a prime, it is likely that the mount mapping for aperture range and minimum aperture are also hard-wired. The only contact with an absolute requirement for electronics is the "data pin", which for an AF prime is required for sharing that an AF lens is mounted and for coordination of AF function.

As for the OP...a refund is probably in order.

Steve

**Bob 256** · 05-12-2021, 06:36 PM

Already seconded, but I'll throw my vote in for refund as well. Something really not right with this lens.

05-12-2021, 01:31 PM	#1
raderstudios Junior Member Join Date: Apr 2021 Posts: 38	DA 35mm 2.4 Focus Problem Hi all, I recently picked up a second-hand DA 35mm 2.4, and unfortunately it seems to be damaged. The autofocus doesn't function at all - no noise or attempt from the body to focus the lens. I have tried the lens on a K20D and a K100, verified that both are in AF mode, cleaned the contacts on both bodies and the lens. Nothing. Also, with the bodies in MF, I have tried focusing manually. The lens will focus optically, but the cameras do not detect focus, won't signal focus, and will not trigger the shutter release. Is there a way to fix this, or is the poor little Plastic Fantastic a goner? Thanks in advance or your help!

05-12-2021, 02:02 PM	#3
raderstudios Junior Member Join Date: Apr 2021 Posts: 38 Original Poster	Thanks for your help! The viewfinder is displaying normally on both cameras. Here's an image (I cheated and used my Pixel phone - I know I'll have to be drawn and quartered now ) Attached Images

05-12-2021, 02:08 PM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	If the camera does not attempt to focus, it generally means that an AF lens has not been detected through the data pin (contact furthest from the lens retention pin) on the camera. That can happen if the matching contact on the lens is non-functional or the internal lens electronics that do the communication are bad. Steve Last edited by stevebrot; 05-12-2021 at 02:13 PM.

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05-12-2021, 01:38 PM	#2
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	This lens should work on your K100D and K20D. Is the camera displaying F-- in the viewfinder? That would mean the electronic part is dead somehow, or contacts not effective but you already cleaned them... Can you share a picture of the back of the poor lens, so I can compare it with my (functional) DA 35 F2.4? If F-- is displayed, I suppose you could try to take shots in MF though, but you will have to enable "Use Aperture Ring" in the setup. This is to allow K and M lenses to work ; it should allow you to shoot the DA 35 as well, but only wide open though, due to lack of aperture ring.

05-12-2021, 02:07 PM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	If the camera does not attempt to focus, it generally means that an AF lens has not been detected through the data pin (contact furthest from the lens retention pin) on the camera. That can happen if the matchning contact on the lens is non-functional or the internal electronics that do the communication are bad. Steve

05-12-2021, 02:22 PM	#6
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	Okay. Looks clean enough. If you manually turn the focus ring, will the screw at the back of the lens turn? It definitely should.

05-12-2021, 02:23 PM	#7
raderstudios Junior Member Join Date: Apr 2021 Posts: 38 Original Poster	Originally posted by Bertrand3000 Okay. Looks clean enough. If you manually turn the focus ring, will the screw at the back of the lens turn? It definitely should. Yes it does.

05-12-2021, 02:30 PM	#8
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	That means that mechanically your lens is fine. If you don't get F-- then the electronic part cannot be fried either. I am at a loss of what is happening here. If you put your camera in aperture priority mode, then stop down to let's say F5.6 and try optical preview, will the aperture close a bit?

05-12-2021, 02:49 PM	#9
Belnan Site Supporter Join Date: Jul 2010 Location: Nova Scotia Photos: Albums Posts: 1,090	That sucks. Sorry not helpful.

05-12-2021, 02:50 PM	#10
Kendra59 Senior Member Join Date: Apr 2021 Location: Kelowna, BC, Canada Posts: 187	Try gently rubbing the electronic contacts with a clean pencil eraser... This often works with other electronics.

05-12-2021, 03:11 PM	#11
ramseybuckeye Site Supporter Join Date: Apr 2009 Location: Hampstead, NC Photos: Gallery Posts: 17,296	If cleaning the contacts does not work, get a refund.

05-12-2021, 03:36 PM	#12
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,379	This might be a dumb question but.......... is your camera in manual or autofocus mode? If it's in manual, autofocus isn't going to do anything but the camera should still detect the focus point and alert you when good focus is manually achieved (it should be working like a generic manual focus lens). Just want to be sure that little switch in in the "autofocus" position.

05-12-2021, 03:44 PM	#13
raderstudios Junior Member Join Date: Apr 2021 Posts: 38 Original Poster	Originally posted by Bertrand3000 That means that mechanically your lens is fine. If you don't get F-- then the electronic part cannot be fried either. I am at a loss of what is happening here. If you put your camera in aperture priority mode, then stop down to let's say F5.6 and try optical preview, will the aperture close a bit? Oh, this highlighted another symptom. The camera won't enter optical preview mode with the lens attached. ---------- Post added 05-12-21 at 03:46 PM ---------- Originally posted by Bob 256 This might be a dumb question but.......... is your camera in manual or autofocus mode? If it's in manual, autofocus isn't going to do anything but the camera should still detect the focus point and alert you when good focus is manually achieved (it should be working like a generic manual focus lens). Just want to be sure that little switch in in the "autofocus" position. Yep, definitely in AF mode. I have played with it in MF mode, too, and the camera will not detect focus, even when the scene is visibly in focus. ---------- Post added 05-12-21 at 03:51 PM ---------- Originally posted by ramseybuckeye If cleaning the contacts does not work, get a refund. That does seem to be the way this is heading...

05-12-2021, 04:46 PM	#14
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Bertrand3000 That means that mechanically your lens is fine. If you don't get F-- then the electronic part cannot be fried either. I am at a loss of what is happening here. While the "A" contact "gates" both aperture control, all it means is that the mount contacts are not evaluated unless the "A" contact is detected. Evaluation of the contacts will result in aperture control (no F--) enabled at minimum, but is no guarantee that AF is also functional. I am pretty sure that most (all?) Pentax lenses having no aperture ring have the "A" contact hard-wired as "present/on". I can't say for sure for the DA 35/2.4, but as a prime, it is likely that the mount mapping for aperture range and minimum aperture are also hard-wired. The only contact with an absolute requirement for electronics is the "data pin", which for an AF prime is required for sharing that an AF lens is mounted and for coordination of AF function. As for the OP...a refund is probably in order. Steve

05-12-2021, 06:36 PM	#15
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,379	Already seconded, but I'll throw my vote in for refund as well. Something really not right with this lens.