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If I have a camera that does not have any electronic connection to the lens, is there any way to adjust the aperture on the lens if it does not have a physical aperture ring?

We're using a scientific camera (Imperx Bobcat) which does not have any electronic connections in the mount for the lens. It mounts Nikon lenses, but the mount doesn't have the necessary electronic connections. This has been fine for us in the past, as we have always used lenses with a physical aperture ring. (We manually focus the lens for our experiments, so autofocus isn't a concern.) We recently gained access to a AF-S NIKKOR 200mm f/2G ED VR II lens, but it lacks a physical aperture ring.

Is there some sort of adapter or 'smart' extension tube that would let us adjust the aperture manually on a lens without an aperture ring? (We typically use extension tubes, so the extra distance is not a concern.) The easy answer is likely to just use a lens with an aperture ring, but we wanted to see if there were any possible options for the above scenario.

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    \$\begingroup\$ If the lenses in question were Canon EF lenses, you could use a Canon body with a DoF preview button to set the lens to a specific aperture (using Av or M mode) and then remove the lens while holding down the DoF preview button. The lens will hold the set aperture until reattached electronically to an EOS body. \$\endgroup\$
    – Michael C
    May 3, 2014 at 0:53
  • \$\begingroup\$ @MichaelClark That's a handy tip; unfortunately our camera uses Nikon lenses. For what it's worth, I saw a suggestion to use this adapter bhphotovideo.com/c/product/37175-REG/Nikon_2658.html which looks like it might work. The caveat being that I assume that there are no detents/stops on the lever on the BR-6. That is, I think I would only know if I was wide open (f/2) or closed down (f/22), but any in-between setting would be unclear... \$\endgroup\$
    – Frank
    May 3, 2014 at 11:47
  • \$\begingroup\$ Which is why I edited your question to exclude lenses other than Nikon. Otherwise the Canon tip would be a valid answer in this format, which is for the benefit of all who have the same question, not just the original asker. \$\endgroup\$
    – Michael C
    May 3, 2014 at 14:35
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    \$\begingroup\$ @Frank, would you be able to select a best answer (edit existing ones if necessary) or provide your final solution for the problem (if you achieved a solution)? This question has been viewed almost 10,000 times, so the community would greatly appreciate any effort you provide to detail the solution. \$\endgroup\$
    – MechtEngineer
    Dec 12, 2017 at 2:00

4 Answers 4

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Ultimately, we decided to use a Nikon BR-6 Auto Diaphragm Ring combined with a BR-2A Lens Reversing Ring, plus a Nikon AR-10 cable release for setting the aperture.

This was the setup: A Nikon lens (lacking an aperture ring) connected directly to the BR-6 F-mount socket. The 52mm threaded rear of the BR-6 connected to the BR-2A 52mm threads. The other side of the BR-2A attached to the F-mount of the camera body. The Nikon AR-10 cable release connected to the BR-6 for manually setting the aperture.

This was admittedly an ugly solution. The BR-6 and BR-2A act like extension tubes (hurting far focus), and you cannot readily set the aperture accurately to a known value (other than wide open or closed). However, for our specific application, these tradeoffs were acceptable. Be advised that in a more conventional photographic setting, these compromises may be far more unpalatable / problematic.

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  • \$\begingroup\$ Hi Frank. Thanks for coming back and answering and accepting! \$\endgroup\$
    – scottbb ♦
    Dec 15, 2017 at 5:18
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As far as I'm aware, the AF-S NIKKOR 200mm f/2G ED VR II lens has a mechanical aperture control, not electronic. The lever that controls the aperture can be found on the lens' mount. You could manually set the aperture by stuffing something such as the plastic part of a cut in half cotton bud in the aperture lever slot to keep the aperture set to what you want.

Wedging aperture lever on a Nikon G lens

Or a better idea would be to purchase a cheap Nikon extension tube and a cheap Nikon G to Canon EF adapter. This adapter has a lever on it that allows you to set the aperture of the lens using the lever, which means you can adjust the aperture easily. Both adapter and extension tubes can be found easily on eBay.

Depending on the extension tube construction, you may be able to unscrew the side that the lens mounts on, then place the adapter on the end instead and glue it in place. Otherwise you might just need to glue the adapter on the end of the tube and add some card and tape round any gaps between the adapter mount and the tube.

Either way, make sure that the lens release lever (on the reverse of the adapter) is accessible, otherwise you won't be able to remove the adapter from the lens. Alternatively you could remove the lens locking pin from the adapter if you are not worried about the possibility of the lens / camera unscrewing from one another.

That will then give you a Nikon mount extension tube with a lever for controlling the lens' aperture.

Once this is done, you will need to make a series of test shots with the aperture lever at different positions, noting the position of the lever for each shot. This will then allow you to get an idea of what aperture setting the different positions of the lever equate to.

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you can jam something into the preview lever that sticks out of the back of the lens and get it to open, you would need to take reading to determine the fstop

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Fotodiox is selling am "aperture control enabler" now that's designed to do this for macro reversed lenses. You could use it pointing the standard direction on a manual camera body if you got the right filter thread adapters, though it will mess up the flange-focal distance, so it's probably only useful if you're using a macro lens anyway or your image quality requirements aren't too stiff.

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