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05-17-2014, 09:23 AM   #1
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What's up with this mini wide?

Hi all,

I recently got a great deal on a pretty nice lot of lenses at an auction site. It included a sigma mini wide 28mm, which I've been wanting to try for a while.
Here's my silly question--it doesn't seem to mount onto my KX. On the side of it, it says "for pentax K" (see below) but it won't actually turn into place when I try to put it on the body.
I'm sure I'm missing something, can someone please fill me in?

Many thanks!
Danielle



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05-17-2014, 10:03 AM   #2
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Hi danielle

Funnily enough there was another thread on the same thing...

https://www.pentaxforums.com/forums/120-general-technical-troubleshooting/238...m-1-2-8-a.html

I don't think that one was satisfactorily resolved. Not the same lens is it...??
Certainly the mount looks like a normal PK from your pics.
edit except that normally the little aperture lever shield is in line with the aperture lever it isn't .... could be an issue???

Do you have a PK extension tube (or eg pk to mft adapter...) by any chance? If you do then try fitting that on, and you can look through the end and maybe see where its getting hung up if it doesn't go on.

Last edited by marcusBMG; 05-17-2014 at 10:09 AM.
05-17-2014, 10:10 AM   #3
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The aperture shield hits the SDM contacts. If you compare it to a regular Pentax lens you will see it is in a different location. I don't think that it can be removed as it can from most other lenses with a similar problem. It has to be cut off with a dremel.
05-17-2014, 10:57 AM   #4
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Side Note: You can also file it down using a metal file and some very, very steady hands, if you don't have a dremel. Just be sure to cover everything else in masking tape before proceeding. (Had to do this with a cheap Vivitar lens before)

05-17-2014, 11:07 AM   #5
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This same lens was the first one I bought after switching to digital and APS-C, to own one "normal" prime. The protecting flange was just a millimeter either too high or to long (or both, can't remember which). I returned it to the seller, who had not known this. Luckily, a short time later I got a near mint Pentax SMC-A 2.8/28 for the same price.

Sigma designed this lens not exactly according to the Pentax K mount specification (probably did not get it from Pentax for free). When they became aware of the problem, they modified the design so it would fit.

The lens will fit to all Pentax K and KA mount bodies, but not to KAF or newer. This means, up to the Pentax P series; with the SF series, the flange will hit the power zoom contacts, which now are used for SDM.
05-17-2014, 11:13 AM   #6
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QuoteOriginally posted by RKKS08 Quote
The lens will fit to all Pentax K and KA mount bodies, but not to KAF or newer. This means, up to the Pentax P series; with the SF series, the flange will hit the power zoom contacts, which now are used for SDM.
The SF series did not have power zoom contacts, the PZ-1 was the first with power zoom contacts.
05-17-2014, 11:59 AM   #7
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I was sure I had tested my 28-80 powerzoom with the SFXn before I sold it.

But now I had a look at that body, and you are right, no power zoom contacts.
Must have been my Z-20, sorry.
05-17-2014, 12:02 PM   #8
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Thanks all, very informative!
I have a follow up question:

I tested it out with an osawa 2x teleconverter that came in the lot and indeed, it works with that combo (though the image quality is absolutely (and somewhat expectedly) terrible).
So I tested it with a short extension tube, and although it mounts just fine, I can't focus at all. Even less so than with the teleconverter. I must be doing something wrong, I think. Especially because the lens looks to be in like-new condition.

Thanks again!

05-17-2014, 12:21 PM   #9
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vintage tc's are mostly pretty rank, and are designed for tp's primarily. Mixing lenses and tc's can be a pretty hit and miss affair, not so surprised that combo didn't give decent results.

Even a short extension tube is going to reduce focus distance with a wide angle l like this to just a few cm. Focus on infinity and move closer and closer... and closer!! should come into focus
05-17-2014, 12:29 PM   #10
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QuoteOriginally posted by marcusBMG Quote
vintage tc's are mostly pretty rank, and are designed for tp's primarily. Mixing lenses and tc's can be a pretty hit and miss affair, not so surprised that combo didn't give decent results.

Even a short extension tube is going to reduce focus distance with a wide angle l like this to just a few cm. Focus on infinity and move closer and closer... and closer!! should come into focus
Thanks marcusBMG. Seems like I have to be about 1cm away from the object- ack!
I guess I'll try my luck at shaving down the aperture shield. The lens was virtually free so I'm not worried about its resale value.
If any one has a link to a tutorial (text or video), it'd be a huge help!

Danielle
05-17-2014, 01:15 PM   #11
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Just cut it right off its not essential, my tokina 28mm doesn't have one. Dremel is good but small hacksaw sufficient. Use cling film to cover the optics etc and prevent filings going where they shouldn't.
if you have some jewellers/modellers screwdrivers you could try taking off the mount to do the cutting off the lens (preferable).
09-28-2015, 04:33 PM   #12
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QuoteOriginally posted by RKKS08 Quote
This same lens was the first one I bought after switching to digital and APS-C, to own one "normal" prime. The protecting flange was just a millimeter either too high or to long (or both, can't remember which). I returned it to the seller, who had not known this. Luckily, a short time later I got a near mint Pentax SMC-A 2.8/28 for the same price.

Sigma designed this lens not exactly according to the Pentax K mount specification (probably did not get it from Pentax for free). When they became aware of the problem, they modified the design so it would fit.

The lens will fit to all Pentax K and KA mount bodies, but not to KAF or newer. This means, up to the Pentax P series; with the SF series, the flange will hit the power zoom contacts, which now are used for SDM.
I used a razor knife and prune down, the errant guard. This is easy to do - it's only plastic. All works good. Took me 15-30 seconds.
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