[beachgardener]

I doubt that a manually set aperture set via an aperture ring is necessarily more accurate than one set using an "A" setting and letting the camera set the aperture

for me, using manually set aperture and shutter, using incident readings can in certain situations be advantageous.

[Mikesul]

Can someone explain why setting aperture with the aperture ring would be more advantageous or accurate than setting it with the wheel on the camera and the ring at the A position? I have done both ways hundreds of times and I cannot imagine how one would be more accurate. It always seems easier to me to use the camera wheel when that is an option.

[beachgardener]

I think I have become confused with the statement, somehow mixed it up with using full manual with hand held meter as opposed to using A setting and camera meter

[JimJohnson]

The aperture ring is obsolete (on DSLRs). Unless you are reverse mounting the lens or something like that, then simply leave the aperture ring in the "A" setting and then set the aperture using the e-dial (or automatically).

I'm one of those "something like that" photographers. Lens reversal, check. Bellows unit, check. Extension tubes, check.
In fact, I go a step further and love to use a bit of foil to fool the camera into thinking all my 'M' and newer lenses (and adapters) are 'A' capable. Then I shoot AV and simply set the lens's aperture ring to match what I dialed in on the camera.
** full confession, there may be a minor exposure mismatch, so bracket when critical. In my experience any slightly off exposure can be handled in post-processing.

[Adam]

I'm one of those "something like that" photographers. Lens reversal, check. Bellows unit, check. Extension tubes, check.
In fact, I go a step further and love to use a bit of foil to fool the camera into thinking all my 'M' and newer lenses (and adapters) are 'A' capable. Then I shoot AV and simply set the lens's aperture ring to match what I dialed in on the camera.
** full confession, there may be a minor exposure mismatch, so bracket when critical. In my experience any slightly off exposure can be handled in post-processing.

A lot of people miss the aperture ring, or simply like the way it works. Obsolete doesn't mean useless, it just means there is a universally-recognized better way of accomplishing the same thing (i.e. electronically instead of mechanically). Hard to argue that IMO Same reason modern phones stopped having a bunch of buttons.

[Racer X 69]

Can someone explain why setting aperture with the aperture ring would be more advantageous or accurate than setting it with the wheel on the camera and the ring at the A position? I have done both ways hundreds of times and I cannot imagine how one would be more accurate. It always seems easier to me to use the camera wheel when that is an option.

When using an A lens for everyday shooting I use the A position and set the aperture with the e-dial. It is convenient, and I can keep my eye in the viewfinder or on the screen if I'm using live view.

But if I am shooting with extension tubes, bellows, or reversed, the e-dial is useless.

Ergo, the aperture ring.

For that reason my focus on lenses has been those with the A setting.

Sure, there is that nifty PK to Nikon lens adapter with an aperture ring that can be used as a workaround for lenses that don't have one. But have collected a nice group of K mount lenses that have the A feature, and they generally produce some great results.

So I don't feel the need to duplicate what I have with the newer lenses made for digital photography.

What I really need is a way to make my M and M42 lenses work like A lenses and be able to set the aperture via the e-dial when mounted directly. I do have a bit of foil on each of them so the camera thinks an A lens is mounted so the information available in the viewfinder is consistent with what I see when a real A lens is mounted.

[stevebrot]

Can someone explain why setting aperture with the aperture ring would be more advantageous or accurate than setting it with the wheel on the camera and the ring at the A position?

The answer lies in the difference in how the opening size is constrained and the strengths of each solution in maintaining consistency. Work the aperture of both type manually and the difference should be obvious. Consider what is being asked of the aperture controller in the body and the coupling mechanisms in the lens and it is fairly amazing that KA aperture control works at all. At least, I am amazed.*

I have done both ways hundreds of times...

As have I and I use the both with full confidence that the exposure will, for all practical considerations, reflect the settings made. For the most part, exposure differences less than 1/3 stop are barely perceptible to the eye and of little or no consequence unless one is doing quantitative evaluation of sensor response. Whether a lens has an aperture ring makes little difference to me unless I am wanting to use it where an aperture ring is a strong asset to the use case. Those include use on K-mount film bodies lacking e-dials, adapted on non-Pentax cameras, or with devices such as bellows or slide copiers.


Steve

* In all fairness, I am also amazed that aperture ring mechanisms allow for adequate performance of that method as well. Some of the mechanisms are pretty cheesy.

[JimJohnson]

What I really need is a way to make my M and M42 lenses work like A lenses and be able to set the aperture via the e-dial when mounted directly. I do have a bit of foil on each of them so the camera thinks an A lens is mounted so the information available in the viewfinder is consistent with what I see when a real A lens is mounted.

Well you are not directly setting the aperture on a M series lens from the body, but you can come quite close. Certainly you can avoid stop-down metering. Aperture priority (AV) mode is a snap - other modes with frequent aperture changes are doable but not as convenient. An old post of mine:
Kr: short contacts to change aperture when using M42 lens ? - Page 2 - PentaxForums.com
Be sure to follow the links to which pins set the lens aperture range, and the final link to a page with photos on tape application.


Sadly, I later found out it won't work with most M42 lenses because the flange isn't wide enough to interact with the K-mount body contacts.

[Posse96]

Hello and welcome

Any K-mount lens, whether Pentax, Sigma, Tamron or otherwise, with a dedicated aperture ring and "A" setting on it allows you to set the aperture from the camera's control wheel by setting the ring to the "A" position. Then, from within any of the P, Sv, Tv, Av, TAv, M and B modes, you select the aperture of the lens using the control wheel on the camera. For lenses without a dedicated aperture ring (e.g. Pentax DA lenses), they operate as those with a ring set to the "A" position.

I don't know what Pentax and Sigma lenses you've been using. Generally, I would say most modern Pentax lenses are great. Older models vary, but are mostly OK-to-excellent. Sigma lenses are, in my experience, much more variable in performance depending on whether they're primes, zooms, and the era in which they were developed and released. Generally, I prefer Pentax lenses. But there are exceptions, such as the DA*16-50, where the Sigma equivalent - in this case, the 17-50 f/2.8 HSM - is arguably better optically.

The latest Sigma lenses can be very good indeed, but those that are compatible with Pentax K-mount sometimes have inconsistent or unreliable auto-focusing, as Sigma reverse-engineered Pentax AF operation when designing its lenses, rather than paying for a licence to use the official specification

Thanks BMC. As I was reading your reply, my brain kicked in and replied; "duh" LOL.

---------- Post added 04-11-19 at 06:09 PM ----------

I respectfully disagree. It is sometimes very useful to set the exposure in M mode, and then depending on the subject/lighting very quickly change the aperture setting on the lens to adjust the exposure (and thus almost instantly get the shot). It requires you to have a reasonable sense of exposure/estimating the change needed, and comfort using the aperture ring--but these are likely normal for many of us--especially coming from the (slide) film era.

True, as when I shoot night stars, while on A on the ring, I do often jump between M and Bulb modes to make my shots.