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10-23-2020, 12:34 PM   #1
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Strange issues

Hi all,
im new to the forum but have had my pentax Kr for about a year , it's never put a foot wrong before but now is acting strange .
Basically my camera will recognise my pentax 18 to 55 kit lens in all modes perfectly.
But my two Sigma lens are at the same time acting like I have attached a manual lens, asking me to input focal length and have no auto features now no auto focus and the aperture dial will register low vales like 1.2 on a 2.8 to 4.5 lens.
So if someone could either assist me or point me to a specific area on this forum where I should be asking I would be grateful.
Thanks Shane

10-23-2020, 12:51 PM   #2
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Clean the contacts of your sigma lenses. they might be dirty.
10-23-2020, 12:58 PM   #3
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Do the Sigma lenses have aperture rings and are they set to "A"?
10-23-2020, 01:08 PM   #4
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Sigma DC 17 to 70 2.8 -4.5
I don't believe it has an A setting on the lens.
Sigma DG 70 to 300 4 -5.6
Does have an A setting.
I can switch between the 3 lenses the pentax perfect every time, either Sigma ask for focal length and display MF regardless of mf/after switch.
I've tried to Google this and have cleaned the contacts as suggested, and just ordered new batteries as I know mine were not brilliant, if all 3 lens had the same issues I'd assume it was the camera but as pentax kit lens is still perfect I'm baffled.
Thanks for your speedy responses Shane

10-23-2020, 03:10 PM - 1 Like   #5
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QuoteOriginally posted by Shaneuk Quote
if all 3 lens had the same issues I'd assume it was the camera but as pentax kit lens is still perfect I'm baffled.
If the camera thinks the attached lens is a manual lens it is because there is a problem with the communication contacts. The problem is finding out what that problem is.
- cleaning the contacts is the first thing to do, on both lenses and camera
- since the Pentax works and the Sigmas don't that implies the problem is with the Sigma lenses
- Non-Pentax lenses might be ever so slightly different than a Pentax lens, not enough to matter usually but can be an issue if something else is loose

- Check the mounts on both the Sigma lenses and on the camera and make sure all of the screws are tight and all of the contacts are present and look correct
- If you have access to another Pentax camera (perhaps a local shop will test for you) try the Sigma lenses there and see if they work
10-24-2020, 06:04 AM   #6
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Welcome to the forum, hope you get your issues resolved quickly
10-25-2020, 08:50 AM   #7
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Hi ,
All thank you for replying and the suggestions, unfortunately I don't have acess to another pentax to test the two Sigma lenses.
I will have to take them and the camera to a shop in the near future but sadly not a dedicated camera in my sleepy dead town.
But one other thing I noticed if I mount an actual vintage manual lens , I input focal length as normal and the Green button gives you a meter reading, the two Sigma lenses that are not being recognised by the camera as auto lenses and acting like manual lenses do nothing when the green button is pressed.
I'm new to photography only about a year of experience so this extra information of the green button only adds to my confusion, hoping that might indicate something to someone else.
It seems ultra weird that two Sigma lenses I've used for a year with no issues both suddenly are not recognised by the camera at the same time.
Thanks Shane
10-25-2020, 10:11 AM   #8
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QuoteOriginally posted by Shaneuk Quote
But one other thing I noticed if I mount an actual vintage manual lens , I input focal length as normal and the Green button gives you a meter reading, the two Sigma lenses that are not being recognised by the camera as auto lenses and acting like manual lenses do nothing when the green button is pressed.
This, to me, is further evidence that the problem is with the Sigma lenses and not your camera.
Just grasping at straws here, but was there a camera firmware update between the last time the Sigmas were working as expected and the time they stopped?

11-03-2020, 07:06 AM   #9
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QuoteOriginally posted by Shaneuk Quote
Hi ,
All thank you for replying and the suggestions, unfortunately I don't have acess to another pentax to test the two Sigma lenses.
I will have to take them and the camera to a shop in the near future but sadly not a dedicated camera in my sleepy dead town.
But one other thing I noticed if I mount an actual vintage manual lens , I input focal length as normal and the Green button gives you a meter reading, the two Sigma lenses that are not being recognised by the camera as auto lenses and acting like manual lenses do nothing when the green button is pressed.
I'm inclined to agree with Parallax and others here - in order for everything to work correctly with a manual lens, the lens' metal mount has to be touching the camera. There's a pin on the camera that needs to short out on the metal to let the camera know there is a lens there. If the pins aren't dirty, is there any possibility they have recessed too far into the lens to still be touching, or that the metal or some adjoining piece has warped in such a way as to prevent contact?

Since two lenses seem to be affected, it's also possible there are two different causes. In any case, as Parallax said, knowing the firmware version might help. I don't know about the K-r specifically, but it's usually possible to up- and downgrade firmware as needed on a Pentax camera, with a little manual editing.
11-03-2020, 07:33 AM   #10
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There is a firmware update for the K-R for the 17-70 lens on the global Sigma site to address issues using this lens. Here is the link: link.

I didn't see any mention of the 70-300, but couldn't hurt to try if the contact are clean as sergysergy and jatrax recommended above.
11-03-2020, 08:47 AM   #11
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QuoteOriginally posted by WhatsMyNameAD67 Quote
There is a firmware update for the K-R for the 17-70 lens on the global Sigma site to address issues using this lens. Here is the link: link.

I didn't see any mention of the 70-300, but couldn't hurt to try if the contact are clean as sergysergy and jatrax recommended above.
Second it... Probably firmware update will do the needful!
11-03-2020, 04:33 PM - 1 Like   #12
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Hi guys, thanks for the replies since I last posted I ordered new batteries just in case anything like insufficient power to operate auto focus, clutching at straws I know but trying to cover all possible reasons.
I ordered 100% rubbing alcohol and have cleaned the two sigma lenses contact points and the camera body points.
I must have sat there now with the pentax kit lens and the two sigma lens and swapped from lens to lens hundreds of times.
Same results kit lens automatically behaves normally every time, both sigma without fail ask me to input focal length.
I will connect and see if there is any firmware updates.
Thanks for your suggestions
Shane
11-03-2020, 11:36 PM   #13
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Welcome to the forum, I'm sure there will be plenty of advice and suggestion around here if you have any issues.
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