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Legacy Lenses Discuss the use of older lenses, using adapters, from the Olympus OM system, Leica M and R-series, and the millions of others too.

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Old 4th February 2010
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Sigma M42 mount to Olympus4/3

I have a Sigma Zoom 80-200mmF4.5 5.6 which I got when I purchased a faulty Pentax ME Super for spares.

I have got a very cheap adaptor to allow me to use it on my Olympes E-450.

My question is this.

The lens adaptor fits fine and for 3.00 posted was areal bargain. However, on the lens there is a pin which when pressed in allows you to adjust the apeture. The adaptor does not press this pin in so the blades are always open. Does any one know of a way to adjust either lens or adaptor.

Does that make sense??
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Old 4th February 2010
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Re: Sigma M42 mount to Olympus4/3

Yep...difficult but start with trying either some tape over the pin or see if you can jam a bit of card in to close the pin...
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Old 4th February 2010
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Re: Sigma M42 mount to Olympus4/3

The lens has an aperture ring on it so that, by turning it, you can manually adjust the aperture. The pin is there for use by the Pentax. By pressing a button on that camera the aperture closes to that determined by the camera's program so that you can see what the depth of focus is before taking a shot. This will not work on your Oly.

If you look through the lens when not mounted on your E-450 and turn the aperture ring you should see the aperture opening and closing. You will have to use your camera in 'A' mode and adjust the aperture manually.

This is how my Minolta lens used to work and which I am now using on my Oly and I presume the Pentax is the same. I don't have a problem.

I don't think I've explained this very well, but I've had a hard day!

Good luck
Bob
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Old 4th February 2010
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Re: Sigma M42 mount to Olympus4/3

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Originally Posted by crimbo View Post
Yep...difficult but start with trying either some tape over the pin or see if you can jam a bit of card in to close the pin...
Hi

That pin, if it's what I think it is, connects to the preview button on the Pentax so that it shuts down to the aperture chosen. You would normally view the scene with the aperture fully open.

Using the Oly you disregard the pin unless it protudes too far into the camera and damages the internals. I would not advise tape or bits of card as this will prevent manual use of the aperture ring.

As I've said earlier, I've had a hard day and I'm probably not lucid now!

Bob
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Old 4th February 2010
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Re: Sigma M42 mount to Olympus4/3

Hi NSS

Ive just thought of something tho' I don't think it makes any difference. Does the pin actually push in or does it move sideways? On my Rokkors it moves sideways but I would think it's there for the same purpose.

Let me know how it all goes. Have you taken any shots with the lens?

Bob
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Old 5th February 2010
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Re: Sigma M42 mount to Olympus4/3

Thanks all for the replys.

The appeture is always open so using the camera in "A" mode is what I have been doing. What I wanted to try was to adjust the appeture to try to get different effects.

The following pictures were taken with the E-450 and a Vivitar lens PK mount on a 4/3 adaptor using different lens settings, and focal lengths from 80 to 200mm. Bear in mind I had only had the camera a month at this time. So was and am still learning and trying to experiment, with light etc etc.










Still new to all this digital stuff.
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Re: Sigma M42 mount to Olympus4/3

Hi

Does your Vivitar lens have an aperture (diaphragm) ring on the barrel? Or is it an "auto" lens in which case aperture control would have been done by the Pentax camera's electronics. As far as I know, you can only use manual legacy lenses with our Olys.

Perhaps some other member can come in here with some more info.

Regards
Bob
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Old 5th February 2010
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Re: Sigma M42 mount to Olympus4/3

As other have said that pin is for the original camera to use auto aperture with the lens. Some lenses have an Auto/Maual switch which makes things a lot easier when using them on a DSLR body.
I have got a couple of Carl Zeiss Jena lenses that luckily have the switch but I also have a Rolleiflex bayonet mount 50mm 1.8 Planar which is auto only that I would like to use with a reversing ring for Macro stuff, I have tried taping the pin down on that without much success and wouldn't fancy trying it with the lens mounted the right way round on the camera incase the tape came of inside.
I think you can get adapters that have a flange on them to push the pin down but I'm not sure where from, or you could try a dab of silver solder on the adapter you already have to work in the same way.

Jon
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Re: Sigma M42 mount to Olympus4/3

Quote:
Originally Posted by BobS View Post
Hi

Does your Vivitar lens have an aperture (diaphragm) ring on the barrel? Or is it an "auto" lens in which case aperture control would have been done by the Pentax camera's electronics. As far as I know, you can only use manual legacy lenses with our Olys.

Perhaps some other member can come in here with some more info.

Regards
Bob
The lens is manual only.

As the apeture rings are always open when the pin is not pushed in, it is not a problem to shoot in "A" mode.
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Re: Sigma M42 mount to Olympus4/3

If the lens doesn't have a stop down (manual aperture) switch, then you need a different adapter.
Both kinds are manual aperture lenses, but the later M42 lenses had a pin that was pushed by the shutter mechanism (or a Dof preview button) that shuts the aperture to the setting on the aperture ring. That allows wide open focussing (which is more accurate) and metering in low light.
Earlier lenses don't have that pin and the diaphragm is directly connected to the aperture ring and will always stop down the lens even if not connected to the camera.

In between, lenses had a little switch that would disconnect the pin and shut the lens down as if it was full manual so they could be used on older bodies without the wide open focussing/metering.
I've got a few of each in a box in the attic, with my old Zenit-E that has an M42 mount.
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