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12-27-2014, 09:24 AM   #1
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K50 and Red F-- at bottom of info screen & shutter won't press with zoom lens

Hi I'm Jayne & I just got a new K50 with a 70-300mm Sigma lens (Pentax fit). I am just learning how to use the basics at moment so using AUTO setting.The camera is working fine with basic lens. However when I tried out zoom lens the shutter release will not press, there is a red F-- at bottom of screen and the F number in screen does not come up as it does with standard lens. I have tried manual setting but same thing happens. I would be so pleased if anyone could help me out with this. I am basically a beginner at moment.

12-27-2014, 09:28 AM   #2
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Make sure the Sigma's aperture ring is in the 'A' position. If not the camera will not be able to determine the aperture setting and you get "F _ _".
12-27-2014, 09:31 AM   #3
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If the Sigma has an aperture ring make sure it is set to 'A'. There is a little button that has to be pressed to move it to 'A'. If it is a later model with no aperture ring there might be an issue with the contacts.
12-27-2014, 09:55 AM   #4
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Have you set the allow aperture ring in the menu. For some reason Pentax is set to not allow it from the factory and you have to go into the menu and change it to allow. That way no matter what the aperture is set on it should work.

12-28-2014, 09:25 AM   #5
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Thanks so much for your help, I pressed the little button on lens as you advised to set it to A and it is all working great now - thanks again for your help 😊
01-23-2015, 08:38 PM   #6
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QuoteOriginally posted by jatrax Quote
Make sure the Sigma's aperture ring is in the 'A' position. If not the camera will not be able to determine the aperture setting and you get "F _ _".
Hi, I have the exact same problem that appeared only today on my Sigma 70-300m lens but all these suggestions have not helped so far. Could it be something else?
01-23-2015, 09:13 PM   #7
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Clean the contacts on the lens and the camera body. Check the lens see if it is in the A position. Check the camera menu is aperture ring permitted.

Rick
01-23-2015, 10:26 PM   #8
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QuoteOriginally posted by tezza Quote
Hi, I have the exact same problem that appeared only today on my Sigma 70-300m lens but all these suggestions have not helped so far. Could it be something else?
Like Rick said.

The flashing F_ _ means the camera is not seeing the lens, or thinks it is an all manual lens. Take it off, remount it, clean the contacts and make sure it is in the 'A' position.

01-24-2015, 03:32 AM   #9
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QuoteOriginally posted by Gizmotabbycat Quote
Thanks so much for your help, I pressed the little button on lens as you advised to set it to A and it is all working great now - thanks again for your help 😊
well done

---------- Post added 01-24-15 at 03:34 AM ----------

QuoteOriginally posted by jatrax Quote
Like Rick said.

The flashing F_ _ means the camera is not seeing the lens, or thinks it is an all manual lens. Take it off, remount it, clean the contacts and make sure it is in the 'A' position.
The contacts are clean as a whistle; if it was them why is it fine with the 50mm lens?

---------- Post added 01-24-15 at 03:54 AM ----------

QuoteOriginally posted by patrick9 Quote
Have you set the allow aperture ring in the menu. For some reason Pentax is set to not allow it from the factory and you have to go into the menu and change it to allow. That way no matter what the aperture is set on it should work.
Well it has been fine with no problem just until today but another thing I have noticed is that no matter the dial mode it just shows aperture priority
01-24-2015, 04:41 AM   #10
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QuoteOriginally posted by tezza Quote
Well it has been fine with no problem just until today but another thing I have noticed is that no matter the dial mode it just shows aperture priority
Another hint that the camera thinks that it can't control aperture of this lens from the body.

If aperture ring is allowed, in "A" position and all contacts on both sides are clean, there could be a contact connection broken inside the lens; or in the camera, but then there would be a problem with other lenses too, of course.
01-24-2015, 10:31 AM   #11
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QuoteOriginally posted by tezza Quote
The contacts are clean as a whistle; if it was them why is it fine with the 50mm lens?
Generally it is the contacts on the lens not the camera that should be looked at. The camera is new, the lens is relatively old. And looking clean is not the same as being clean. The voltage here is very small, it takes little to interfere.

If you are getting a flashing 'F _ _':
  • Check that 'use aperture ring' is enabled in the menu
  • Take off the lens and examine the lens contacts, are they all present? All protruding as they should be? Clean and free of tarnish?
  • Using a clean micro-fiber cloth gently buff the lens contacts and the camera contacts
  • Remount the lens and try again.
  • Try taking the lens out of the 'A' position, what happens? Put it back in 'A' does the behavior change?
  • Try wiggling the lens slightly on the mount some third party contacts are not precisely aligned or have a little more play in them.
  • Test with a different lens preferably one that also has an aperture ring. Is the behavior the same? Try with the aperture ring NOT in the A position, what happens?
If none of that works and other lenses do work, I would suspect a broken contact in the lens.
01-24-2015, 11:49 PM   #12
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QuoteOriginally posted by jatrax Quote
Generally it is the contacts on the lens not the camera that should be looked at. The camera is new, the lens is relatively old. And looking clean is not the same as being clean. The voltage here is very small, it takes little to interfere.

If you are getting a flashing 'F _ _':
  • Check that 'use aperture ring' is enabled in the menu
  • Take off the lens and examine the lens contacts, are they all present? All protruding as they should be? Clean and free of tarnish?
  • Using a clean micro-fiber cloth gently buff the lens contacts and the camera contacts
  • Remount the lens and try again.
  • Try taking the lens out of the 'A' position, what happens? Put it back in 'A' does the behavior change?
  • Try wiggling the lens slightly on the mount some third party contacts are not precisely aligned or have a little more play in them.
  • Test with a different lens preferably one that also has an aperture ring. Is the behavior the same? Try with the aperture ring NOT in the A position, what happens?
If none of that works and other lenses do work, I would suspect a broken contact in the lens.
Yes thanks jatrax I will try that;but I do not know or can see these contacts on the lens, but it is quite a few years old & one of the cheapest to boot so.....
see how I go
01-24-2015, 11:51 PM   #13
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QuoteOriginally posted by RKKS08 Quote
Another hint that the camera thinks that it can't control aperture of this lens from the body.

If aperture ring is allowed, in "A" position and all contacts on both sides are clean, there could be a contact connection broken inside the lens; or in the camera, but then there would be a problem with other lenses too, of course.
O.K. thanks for that; still trying out things
01-25-2015, 12:26 PM   #14
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QuoteOriginally posted by tezza Quote
Yes thanks jatrax I will try that;but I do not know or can see these contacts on the lens, but it is quite a few years old & one of the cheapest to boot so..... see how I go
Look at the lens mount, you should see a series of small metal balls sticking up through the plate. These are spring loaded and make contact with the contacts on the camera plate. The number will vary from 1 to 6.

However, if you have no (zero) contacts then you have an older all manual lens. In this case the camera must be in the 'M' manual mode and you need to use "green button" stop down metering.

Please post a picture of the lens mount without glare and we can tell you quickly what you have. Also post the exact name and description of the lens or a picture so we can tell what model you have. Sigma has made a number of 70-300 lenses over the years so that is not enough to tell which one.
01-26-2015, 09:23 PM   #15
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k50 F-- flashing on 300mm lens

Have gone back to the source the retailer & we have come up with a compromise; in Menu just toggle enable/disable aperture ring when swapping lens
& that works & for the age of the lens & the No. of times I use it...quite happy. Thanks for suggestions which were all around it. Much appreciated

---------- Post added 01-26-15 at 09:26 PM ----------

QuoteOriginally posted by patrick9 Quote
Have you set the allow aperture ring in the menu. For some reason Pentax is set to not allow it from the factory and you have to go into the menu and change it to allow. That way no matter what the aperture is set on it should work.
Yes, that was it.Bingo! Thanks

---------- Post added 01-26-15 at 09:29 PM ----------

QuoteOriginally posted by Gizmotabbycat Quote
Hi I'm Jayne & I just got a new K50 with a 70-300mm Sigma lens (Pentax fit). I am just learning how to use the basics at moment so using AUTO setting.The camera is working fine with basic lens. However when I tried out zoom lens the shutter release will not press, there is a red F-- at bottom of screen and the F number in screen does not come up as it does with standard lens. I have tried manual setting but same thing happens. I would be so pleased if anyone could help me out with this. I am basically a beginner at moment.
Look at disable/enable aperture ring in Menu
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