Problems with Sigma 24mm Superwide lens

Hi, seem to be getting a few problems lately, turns out my focusing issue with my K5 was more down to user error than camera error but now I have a different problem.
I have a manual focus Sigma 24mm f2.8 lens and for some reason the when I change the aperture on the camera it will not go down past f4 it will go up to 22 but not past f4. The lens is definitely set to the "A" setting and I have tried another lens that goes down to f3.5 no problem. Any ideas anybody?

Thanks in advance

Lee

Sounds like the contacts..... Try cleaning them. Waggle the lens about a bit when fitting it.

Top lens.

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I've tried waggling contacts look clean.

Is the set to Manual metering? It should be.

Are you using LV, because LV closes the aperture down automatically if the scene is too bright.

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Hmmm! I've got 2 of these and I just tried one on a K-5. It was already set to 'A' and the aperture only worked from f/4 to f/32. I pressed the green button to take a meter reading at f/4 and then set the lens off 'A' and at f/4 manually. Slight difference in readings could even be a stop.

Without touching anything else I set the lens to 'A' again. This time it went down to f/2.8 so maybe you have to set 'A' on the camera with it switched on.

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It's very strange, pretty sure i have used one of these on my K5 before with no problems.

I used to have the manual focus "A" version and now have the AF version, both work(ed) fine down to f2.8 on my K5. Normally the problem is dirty contacts on the lens (or occasionally body) Give them a clean with a lens cloth and see if that helps.

Mine also works well on a K5-lls

It worked fine yesterday for a few hours I have checked the first photos I took and they are definitely at f2.8, all the contacts are spotless, tried all kinds of things and it still won't go below f4.