K20 Display cuts out with Sigma Lens

Whenever i put my Sigma lens on the K20 an odd thing happens;
When trying to make changes to the settings using menu or Fn button the rear screen goes blank , usually after a few seconds, but the actual time to blankness varies between 2 and 10 seconds. The lens functions perfectly, AF and aperture changes with no problem.
Have cleaned the contacts, but still no difference. I have never seen this happen with any other Pentax or 3rd part lens.
Any ideas?

Davex.

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K5 + 8mm-500mm zooms and primes
Please feel free to play with any images I post.
My flickr: link

Have not had that problem but I have had the rear command dial stop working when, and only when, a brand new sigma 20mm EX DG lens was attached. Have had no problems at all with any other Sigma AF lenses, which are 5-15 years old. Very odd - I wonder of the latest EX DG lenses have a bug?

Could it be the chip in the sigma lens?

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Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

How to tell? what to do about it?

Davex.

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K5 + 8mm-500mm zooms and primes
Please feel free to play with any images I post.
My flickr: link

Contact Sigma, they might be able to tell by series number what chip is in it and if it needs an upgrade/replacement for it to be compatible with the newer Pentax cameras.
I don't know who pays the bill.

Instead of Pentax making sure the lenses fit, Sigma makes sure the Lenses fits the camera that's why older lenses sometimes does not work correctly.

here is something on flickr about it http://www.flickr.com/groups/sigma_lenses/discuss/72157606282211513/

here is the contact information for Sigma.
http://www.sigma-photo.co.jp/english/network/index.htm

The thing is your lens seems to work okay so I think something else is going on, you could check you exif data if the lens focal length and that sort of thing show up properly.

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Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

Dave, do you use a grip with your K20D?

If so, you may be inadvertently touching the shutter button on the grip with the palm of your hand when you're holding the camera to look at the screen. It might only happen with the Sigma because it's a heavier lens that needs more support, and you're holding the camera slightly differently. Just a thought. See this thread for something (a bit) similar, and this one for something more similar.

Cayman, as you use a grip too, does this sound familiar? I know you've only experienced it with one lens, but could it be coincidence? Do you always get the malfunction, or has it happened once or twice with this lens only?

Dan

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K-3, a macro lens and a DA*300mm...

Dan - thanks for the advice. I had not checked if one wheel was between clicks but will do if it ever happens again. To be honest the Sigma was such a bad lens (would not produce a sharp image) I returned it after only a few days. Have not had any similar problems with any other lens before or since.

Thanks for the info Stefan, Dan.
Do not use a grip but will check the stray finger idea later today.
Failing that guess it`s back to Sigma.

Davex

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K5 + 8mm-500mm zooms and primes
Please feel free to play with any images I post.
My flickr: link