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01-04-2007, 11:17 AM   #1
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Sigma lens on the new K10D

Hi all,
Having a little problem working out how to use a older lens on my K10D.
I have a 28mm f2.8 sigma.
I have adjusted the custom setting for the aperature ring.
Now when I set the aperture on the lens to 2.8 and shoot everything looks great, the info says f2.9 1/15. Now when i adjust the aperture ring to say f8. I take a photo with the same speed and I get the same photo f2.8 1/15. I have the same results in tv and av
If i shoot in M I can adjust both and adjustment does affect the pictures, but I get no advice on exposure so have to guess.
I am sure I am doing something basically wrong.

Can anyone advise on this?

Regards
Lee

01-04-2007, 12:42 PM   #2
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I think you will have to treat this lens as a Pentax M lens. You have to use the camera in Manual position. Set the f stop then hit the green button. That will set the proper shutter speed for the lighting at that moment. Not really difficult, and with the preview, you can adjust exposure as necessary.
Now, if the lens has an "A" position, then you simply set it to A and treat it as if it were an auto lens, except you have to focus manually.

Walt
01-04-2007, 01:07 PM   #3
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QuoteOriginally posted by newtmaker Quote
I think you will have to treat this lens as a Pentax M lens. You have to use the camera in Manual position. Set the f stop then hit the green button. That will set the proper shutter speed for the lighting at that moment. Not really difficult, and with the preview, you can adjust exposure as necessary.
Now, if the lens has an "A" position, then you simply set it to A and treat it as if it were an auto lens, except you have to focus manually.

Walt
Oh thanks, I completely forgot about the green button.
I could get it to work int he A position, except it wouldn't read the lowest fstop that being 2.8. I think it went to either 4 or 5.6.
01-04-2007, 01:08 PM   #4
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QuoteOriginally posted by newtmaker Quote
I think you will have to treat this lens as a Pentax M lens. You have to use the camera in Manual position. Set the f stop then hit the green button. That will set the proper shutter speed for the lighting at that moment. Not really difficult, and with the preview, you can adjust exposure as necessary.
Now, if the lens has an "A" position, then you simply set it to A and treat it as if it were an auto lens, except you have to focus manually.

Walt
Yes, this is quite right. There has been a few people on the other forum who have complained about overexposure with manual lenses, but I've not had a problem with mine.

01-04-2007, 01:35 PM   #5
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if its set in the A position all u should have to do is manually focus it.. everything else should work as normal..

if its not in the A position or it dosnt have an A position i think u would have to treat it as a none A or poor manual lens..

an old sigma lens will work just the same as an old pentax lens..

trog
01-04-2007, 03:05 PM   #6
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ok but if I set it to A position, which it does have, and I try to lower the aperture on the dial, I can only go as low as 5.6 it wont let me drop to the 2.8.

So my question is, should the camera recognise that the lens has a f2.8? if it should, I can then assume that is my Sigma that is giving the camera grief.
01-04-2007, 03:08 PM   #7
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YEs it sound like something is wrong... this may sound silly but have you tried cleaning the contacts on the lens... may make no difference but I have had old lenses play up when the contacts were real dirty... Though in a different way than you have encounted..
01-04-2007, 03:33 PM   #8
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QuoteOriginally posted by joele Quote
YEs it sound like something is wrong... this may sound silly but have you tried cleaning the contacts on the lens... may make no difference but I have had old lenses play up when the contacts were real dirty... Though in a different way than you have encounted..
No didnt think of that, It has been sitting around for a while. Will try anything.
thanks

01-05-2007, 10:05 AM   #9
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QuoteOriginally posted by joele Quote
YEs it sound like something is wrong... this may sound silly but have you tried cleaning the contacts on the lens... may make no difference but I have had old lenses play up when the contacts were real dirty... Though in a different way than you have encounted..
Well, you wouldn't read about it, but yet I did.
Last night, took off the lens, gave it a bit of a clean, blew on it. Put it back on and Voila, readings down to 2.8
Thanks for your help. Have it all working now. The little green button is so helpful
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