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K-3 M42 Lens Mod


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#1 Will Montgomery

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Posted 21 October 2005 - 06:57 PM

The Issue:

I have a Mirage 28mm M42 mount lens that I want to use on my K-3. To make the aperature fully manual, I have to get the little pin to stay in.

I've done due diligence and searched for this topic and I've seen a few posts about pushing in the little pin and jamming it so it stays there. Can't get this lens to do that... any other ideas?

If not, I'd love to hear more recommendations on a M42 lens that works well without having to modify it.
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#2 Charles MacDonald

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Posted 21 October 2005 - 08:03 PM

I have a Mirage 28mm M42 mount lens that I want to use on my K-3. ....t pushing in the little pin and jamming it so it stays there. Can't get this lens to do that... any other ideas?

If not, I'd love to hear more recommendations on a M42 lens that works well without having to modify it.


The K-3 basicaly uses the same lens mount as the Pentax Spotmatic and the Ricoh Singlex. most lenses made after about 1963 for these have an automatic diaphram, so that a sill camera can have the lens wide open until the moment of exposure. Most had a switch at the side marked A-M ... In the M position the lens stays stopped down. When the pentax SPF came out with full appature metering that switch started to dissapear. The Pentx lens have a little hidden lock that prevents the lens from being put in M on less it is on an older camera (little tiny pin on the part of the lens that hits the lens flange) The aftermarket lens folks just left it off as a cost saver. The Original spotmatic would also stop the lens down with the meter switch.

Providing a way to press the stopdown pin would not make sense in a movie camera.

Without trying on a K-3 I can't give a positive recomendation. If I was looking for a 28 MM lens I would probaly look for a Super Multi-coated Takumar for pentax, and make sure that it did have the auto manual switch. Vivitar and soligor alos made decent lenses, but they may not have considered the degree of enlargement that using the center of the frame to shoot 16mm involves. (pentax did not either, but they probaly did try to make a darn good lens.

Note that the pentax 28mm lens is a f3.5, a lot of the off-brand 28mm are 2.8
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#3 Will Montgomery

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Posted 21 October 2005 - 08:32 PM

I see some of these on eBay with the auto switch... guess I'll try for one of those. Just wish I could trick this lens into working properly.

I notice that I seem to shoot with the K-3's lens on the widest setting (17) the most, so I will look for a 16mm lens as well.
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#4 Chris Keth

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Posted 22 October 2005 - 03:23 PM

I see some of these on eBay with the auto switch... guess I'll try for one of those. Just wish I could trick this lens into working properly.

I notice that I seem to shoot with the K-3's lens on the widest setting (17) the most, so I will look for a 16mm lens as well.



Why don't you just dab a little flux on the pin, push it in a couple times and solder the pin in permanently...very carefully?
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#5 Charles MacDonald

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Posted 22 October 2005 - 08:30 PM

Why don't you just dab a little flux on the pin, push it in a couple times and solder the pin in permanently...very carefully?

1) For that mater, a little bit of expoxy could be used, or even perhaps opening the lens up and removing the spring, Thta method would alow you to sell the lensoff later if it turned out to be not sharp enough, a Still camera user would probaly WANT the auto diaphram to work.

2) a 28MM lens for a still camera is probaly about as wide as you will find at anywhere near a usable price. The still lens have to be made so that they can clear the Mirror in the still camera. THere may be some Russian wider lenses made specialy for the K-3 that you might find cheaper. I think that you can get away with a lens that goes back behind the mount on the K-3 , one that would hit the mirror on a SLR.

(My experience is all with M42 still cameras and not with the K-3)
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#6 Nate Downes

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Posted 22 October 2005 - 09:14 PM

I've found 24mm, 16mm, 12mm and 8mm wide-angles in M42 mount, it's not hard if you do a little digging.
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#7 Bon Sawyer

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Posted 23 October 2005 - 06:02 AM

The Zenitar 16mm f/2.8 and Peleng 8mm f/3.5 are both available new and cheaply in M42 format on eBay.

They're both fisheyes, but don't really appear so when used with the K3, since the 16mm frame uses only a small section in the centre of the images the lenses produce (which is far less distorted than the outer edges that would appear when using the lenses on 35mm cameras).

-Bon
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#8 Robert Glenn

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Posted 23 October 2005 - 10:25 AM

how wide does the zenit zoom lens go before the image vignettes? 25mm?
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#9 jeremy edge

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Posted 24 October 2005 - 11:37 AM

This is how i got the pin to stay on my mc zenitar 16mm:

Take a fountain pen and push the pin all the way down into the lens body.Try to get it to move to the side so it stays trapped inside the lens body.

Crude...but works.
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#10 Nate Downes

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Posted 24 October 2005 - 01:10 PM

how wide does the zenit zoom lens go before the image vignettes? 25mm?


It doesn't, it's designed for 16mm.
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#11 Joe Gioielli

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Posted 24 October 2005 - 03:57 PM

I read on a site that K3 make have problems with the Super Takumar lens. It seemed there was a jamming issue that made it hard to remove the lens. Don't know if it's true or not as I know nothing about the STs, but it might be worth double checking before you buy a Super Takumar.

Good Luck with the project.
Joe
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