Using OM lenses - aperture control

[russell]

Hello,

Sorry to mark my first post with a question that's probably been answered before, but search won't let me search for 'om'!

I would like to know, how do you stop down adapted OM lenses? Looking at the adapters available on eBay, they do not appear to couple to the aperture ring and diaphragm linkages on OM lenses.

So what do you do, hold down the DOF preview button when taking the shot?

Not too great when using a tripod to avoid shake! Has anyone come up with a contraption to hold it in? (Wouldn't imagine a rubber band would exert enough force?)

 

[Luckypenguin]

The adapters have an internal tab (often a screw) so that when the lens is mounted the lever that stops down the aperture is held in place. It essentially works the same as having the dof preview button permanently pressed down.

 

[Fiddler]

Welcome and Hello from Scotland

I use OM lenses myself, and they work well.

All the best,

Colin

 

[russell]

The adapters have an internal tab (often a screw) so that when the lens is mounted the lever that stops down the aperture is held in place. It essentially works the same as having the dof preview button permanently pressed down.

Ah right -- so the live view works OK even when you have the lens stopped right down? (Not too dark/noisy?)

 

[Luckypenguin]

Depends on the prevailing light conditions. On a bright day where I live the screen view is fine even at f11. In darker conditions you may need to focus wide open and then choose you aperture.

 

[bilzmale]

You may have to use 'stop-down' focussing - ie focus wide open and then stop down to shoot. In A mode the camera will take care of exposure.

 

[russell]

Thanks!

One more question on a related note -- what about the DOF markings on the lens? I would assume that for equal print size from a smaller sensor, you would want a smaller circle of confusion and so have a narrower effective DOF than you would for a full frame sensor with the same lens, aperture and subject distance.

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Is there a simple trick you can do like pretend you're actually 1 stop faster in aperture when choosing which marks to use on the barrel?

 

[Brian S]

You must manually stop down the lens, and Liveview will give you the actual depth of field for the image.

Remember that DOF marks on a lens are very subjective, and make a number of assumptions about scene content and viewing distances. As the lens is stopped down at the time of exposure, and you have "Liveview" for the image- What you See is What you Get.

 

[WT21]

Thanks!

One more question on a related note -- what about the DOF markings on the lens? I would assume that for equal print size from a smaller sensor, you would want a smaller circle of confusion and so have a narrower effective DOF than you would for a full frame sensor with the same lens, aperture and subject distance.

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Is there a simple trick you can do like pretend you're actually 1 stop faster in aperture when choosing which marks to use on the barrel?

DOF is similar to FF, but off by two stops, and remember Field of View (FOV) is also narrower as if the FL were doubled. So, a 50mm 1.4 lens at 1.4 on an m43 camera will give you similar FOV and DOF as a 100mm 2.8 lens on FF (though exposure is still at f/1.4). Makes the math simple! You sound experienced, so once you try it out, you'll understand pretty quickly.

 

[russell]

Thanks .. a full 2 stops, that is a fair amount. I have just checked that with an online calculator and it matches. Just to extend your example a little, your 50/1.4 on MFT also has the same DOF as a FF 50/0.7 (but of course a smaller FOV).

Like Brian I have mostly used DOF preview or bracketing but do use the markings when I wanted it on the hyperfocal distance. It will be helpful to know I choose the markings for 2 stops faster than the actual setting.

 

[WT21]

Thanks .. a full 2 stops, that is a fair amount. I have just checked that with an online calculator and it matches. Just to extend your example a little, your 50/1.4 on MFT also has the same DOF as a FF 50/0.7 (but of course a smaller FOV).

Yes , as long as you always control for the same framing. Which is why Voigtlander made the 25mm 0.95, so it acts like a 50/1.8 in terms of DOF.

Like Brian I have mostly used DOF preview or bracketing but do use the markings when I wanted it on the hyperfocal distance. It will be helpful to know I choose the markings for 2 stops faster than the actual setting.

I don't use hyperfocal much, so I couldn't say, but I think it's a linear relationship, so it should hold true, but perhaps others can comment.