Command dial & Manual lens function help?

[Derek of Venango]

Greetings. I need confirmation or correction concerning command dial function on my D-750 with manual lens.

I thought that the body dial can be used to set aperture (if desired) instead of lens aperture ring, but the lens needed to be set on minimum lens setting, e.g. f/22. This is not happening on my Nikon with either Zeiss 25/2.8 nor Voigtlander 40/2 CPU lens. Do you think my D-750 is boinked?

Thanks,
Derek

[Jack Dahlgren]

What happens mechanically is that there is a small button on the mount which is depressed when the lens is set to min aperture. Those lenses may or may not engage that button. Compare to whatever Nikon's you have to see if they have the same configuration. If not, then there is nothing you can do. If so, then you will need to explore futher.

[Derek of Venango]

Interesting, thanks Jack.

Unfortunately, I don't have any manual Nikon glass here to try.

[Birna Rørslett]

The feature is enabled in Section f of the Custom Settings. Nikon keep shuffling the actual position around so thus some models have this under f4, some f6 or f7 or other places. Check your camera. The relevant point is labelled Controls and its submenu Customize Command Dials. There there is a menu choice for Aperture Setting. The default is ON (by selecting control by sub-command dial), which turns the camera into using the command dial to change aperture value on all compatible lenses. Non-G/E lenses need to have their aperture ring set (and locked?) to the minimum value otherwise the error message FEE blinks. If instead the option OFF is selected (option Aperture Ring), then you can use the aperture ring on the lens to set aperture on any lens with aperture ring, and use the dial for all others.

However, having a lens with a nicely functioning aperture ring like the CV 40/2 and insist on setting aperture by the camera dial is to discard an ergonomic feature for something much less optimal. My view.

[Jack Dahlgren]

Interesting, thanks Jack.

Unfortunately, I don't have any manual Nikon glass here to try.

The button is at about 7:30 if you are looking at the lens mount from the lens side.

[Derek of Venango]

Alright-y then. Clearly operator error! Thanks Jack and Birna.

Birna, thanks for the elucidation. Now I see that it is an either/or solution and wasn't aware that one needs to menu dive to activate it. Non the less, I fully agree with your view on using the lens ring over the command dial and is precisely why I bought the above primes. I was curious to see if/how the command dial function worked and as a parity check.  Also, on the D-750 the cheese is moved to f5.

Happy to report diagnosis done and all is well with camera and lens'in question! Equally happy, f5 aperture is "off" and likely permanently hibernated.

And Jack, I appreciate your input as well. Just looked at my body mount, and more than cheese moved this time as the button on my D-750 body is right at 3 O'clock.

[Hugh_3170]

Derek, I would follow Birna's advice for higher specification Nikon cameras such as your D750 which have a rotating aperture follower Tab to electro-mechanically supply the camera with the aperture setting on the lens.  The rotating metering Tab enables the camera to additionally provide metering support for older Nikon lenses (AiS, Ai, and A converted lenses) - see also the menu option where the specifications of such older non-CPU lenses may be manually input to the camera body.

The microswitch located at 7:30 is only found on lower specification cameras such as the Nikon D7500 which do not have an aperture follower Tab, which is what I think Jack may be thinking of. 
These cameras require the lens to be CPU equipped to perform their metering functions.  It is both confusing (number wise - D750 vs D7500) and a big shame that the D7500 is not also equipped with an aperture following  metering Tab, as its immediate predecessor the D7200 does have the Tab.

The button is at about 7:30 if you are looking at the lens mount from the lens side.

[Derek of Venango]

Thanks Hugh.

Interestingly, your last sentence is one reason why my brother opted for the 7200 over the 7500 last summer. He has legacy glass from FM2 days and wanted compatibility. At that time I chose the "high" road (so I thought) and went Oly OM-2n. (;

Aside: The CV-40 is a delight on the D-750 and I like the feel of the dampening better than my Zeiss. Next in my hunt will be a manual 20MM prime.

[Hugh_3170]

Maybe hunt down a late model CV-20 with the updated CPU?

Or one of Nikon's 20mm MF offerings?

Avoid the early versions of the CV-20 lens, as there were exposure errors with it due to poor CPU programming.  The optics were OK, just that the CPU was not quite right.
(BTW, is there anyone here that has the serial number ranges for the old and new versions of this lens? Roland? )

[Derek of Venango]

Hello Hugh.  Welcomed input. I'm not familiar with the CV-20 iterations.Still quite open to input but was thinking of the current AIS Nikon 20mm/2.8. Also, possibly look into the Zeiss 21/2.8 Distagon or Milvus.

[Matthew Currie]

One other thing to note is that some instances of the otherwise very nice 20/2.8D are bothered by clouding in one of the internal lens elements.  I had this and someone else on the forum noted that I was not alone in this.  I note also in my occasional search for parts lenses on Ebay that when the ads are honest it often turns out they're clouded inside.  It apparently affects only some, and may not be a problem in either later ones or in pre-D models, but if you're looking in that area you should make sure that it's clear. I tried ordering a new element from China but they sent the wrong one.  My local repairman tried ungluing and regluing it, but the stuff now available apparently has a different refractive index and the lens though clear and working was sufficiently soft that he ate the repair.

[pluton]

Hello Hugh.  Welcomed input. I'm not familiar with the CV-20 iterations.Still quite open to input but was thinking of the current AIS Nikon 20mm/2.8. Also, possibly look into the Zeiss 21/2.8 Distagon or Milvus.

Reports are wildly mixed on the CV 20/3.5. From  "It's great" to "It's awful".  Sample variation, maybe?
It is an attractive lens because of its size and mechanical design. It would be best to buy it with option to return.
I have used the Nikon 20/2.8 AiS and the Zeiss 21/2.8.  Excellent results can be obtained with each.

[Jack Dahlgren]

I have the 20mm UD, the 20mm f/3.5 AI, and the 20mm f/1.8 G. Also the 18mm f/3.5 AI. The f/1.8 G is generally best. The f/3.5 is most compact. The UD looks cool. The 18mm has a lot of vignetting which is nice when you want it, but bad when not. If you are going with 3rd party lenses I’d wait until they release in native Z mount instead of through an adapter. FTZ works well, but it will be nice when it is no longer necessary.

[Roland Vink]

I thought that the body dial can be used to set aperture (if desired) instead of lens aperture ring, but the lens needed to be set on minimum lens setting, e.g. f/22. This is not happening on my Nikon with either Zeiss 25/2.8 nor Voigtlander 40/2 CPU lens. Do you think my D-750 is boinked?

Note that you can only use the command dial to set the aperture if the lens has a CPU. With non-CPU AI and AIS lenses you must set the aperture by the aperture ring, regardless of how the camera is set. That is no bad thing, I far prefer using the aperture ring on the lens...

[Derek of Venango]

Keith and Jack: Yes the sea of Nikkor 20mm glass is daunting regarding IQ and intended use. Many here seem to like the UD and the /3.5. I'm strictly looking for landscape toward infinity as my Zeiss 25/2.8 is more "artsy" close in, so to speak. Hence, trying to sort through the chaff.

Roland: Command dial is not my priority and I agree. Aperture ring just seems more ergonomic. Good reminder too as I now know that AI & AIS lens will be lens ring only. (:

Further guidance on a 20mm will be greatly appreciated.