[Gary H Perth]

I have both and have had multiple copies of both. The aperture ring of the A series is prone to failure, becoming rough and gritty to use and maybe even jamming the whole mechanism at some point. In my experience the A series is slightly sharper wide open than the M but despite that I usually go for the M because it's more pleasant to use due to it's superior build quality and I don't have to worry that it might break down on me. I use them on both film and digital so I need a working aperture ring on the lenses. As has already been said, if you're going to use it only on digital and without reversing it or using any extension tubes or anything, then you can leave an A lens in the A position and you won't have any problems.

I recently acquired two different 50mm lenses on the same day. I picked up a well used Pentax A 50mm f1.7, and I plan to keep it on A setting for a general purpose light walkaround lens that I can use on program, scene or Av settings, and take a couple of seconds to focus. It seems very sharp and gives good colours, but this is just an hour's walking around in mid afternoon under clear sunny sky. Further tests await. The second pickup was the Sigma 50mm f2.8 Macro, which is incredibly sharp over the full range from 0.1m to infinity focus. This meets all my 50mm needs, and with 1:1 macro it saves me needing tubes or rings of any sort (and the autofocus is spot on even at full closeup). So if I want to be as low-key as possible, I will take the A 1.7, but if I am likely to be interested in cerious closeup work I have the Sigma.

Notes: Also in my kit I have a FA50mm/f1.4 and a 40mmf 2.8, so there's the evidence you need that my LBA is uncontrolled. The only upside to having so many 50mm lenses is that I can now sell my M40-80mm "macro" without a worry. A real heartbreaker from about 10 years ago was a severe fungus outbreak that destroyed the internal glass in my M50mm f1.4 and M50mm f1.7.

I hope to have some time in the next week or two to test the three 50mm lenses as a careful comparison.

[paulh]

The reason I like M over A is because I like picking the aperture instead of letting the camera do it automatically.

This isn't how A-lenses work. You select the aperture by using the camera's control wheels instead of the lens' aperture ring. The camera doesn't "automatically" pick the aperture for you unless you're in auto mode or using one of the scene modes.

[gofour3]

There are always workarounds, of course, and sometimes those require purchase of a lens with an aperture ring. Last, but not least is backward compatibility to one's favorite K-mount film camera.

A working aperture ring is a nice thing to have.

Exactly!

I have many Pentax lenses with the "A" setting on the aperture ring, but never use them that way. So a functioning aperture ring is a must for me with my film cameras.

Phil.

[reh321]

YOUR ANSWER is the Best, not sure why it should matter anyhow if the aperture is set in the A position as it should be>

When I shot with my Super Program, which was kitted with a 'A 50mm f/1.7', I could shoot in the equivalent of 'Av' mode only by using the aperture ring. The aperture ring did have a "hitch" between f/8 and f/5.6, but it survived over twelve years of this activity. Today the "hitch" is still there - but the lubrication seems to be drying, so focusing beyond 30 feet or so has become almost impossible. I still use that camera on occasion, but right now its primary lens is a Takumar 50mm f/1.4.

[mikesbike]

You used the term "electronic control" several times. FWIW, there is only one lens in the history of the K-mount that supports electronic aperture control. That is the DA 55-300/4.5-6.3 with KAF4 mount where there is no physical control/actuator coupling with the camera. Control on that lens is "by wire". All others have purely mechanical control, either through an aperture ring or by the body through the actuator coupling.**

There are many advantages to using lenses supporting body-controlled aperture (you listed most) and also a few distinct disadvantages when lacks the option of a functioning aperture ring. Examples include (most) extension tubes, non-compliant tele-converters (do any support KAF4?), macro with reversed lens, mirrorless and other other adaptations, and (of course) all bellows. There are always workarounds, of course, and sometimes those require purchase of a lens with an aperture ring. Last, but not least is backward compatibility to one's favorite K-mount film camera.

A working aperture ring is a nice thing to have.


Steve


(...are we far enough off-topic yet?)


* Pentax jargon for body control of the aperture for exposure or DOF preview. This is to differentiate from "Automatic Aperture Actuation" (aka "auto aperture"), a completely different lens feature.

** The better K-mount adapters for mirrorless cameras actually provide an aperture ring that mechanically couples to lenses lacking such.

My bad semantics, borrowed from magazines of yester-year when describing (and measuring) difference between setting aperture via the ring or camera body. Of course I know about the Kaf 4 lens pertaining to electromagnetic diaphragm control. And yes, there are some uses for having the ring.

In fact, there are some otherwise desirable Pentax AF 35mm film camera bodies, even the last flagship model, the MZ-S, which required use of the aperture ring for user-selection of aperture. In some cases, I've held on to certain lenses having the aperture ring specifically because I have this camera.

---------- Post added 11-15-18 at 04:57 PM ----------

So, in a nutshell: An aperture ring is a beautiful thing.

It certainly can be, for the reasons given. BTW, that's a good, sharp 50mm, very good even wide open, which is a rare thing for fast, wide-aperture lenses. Great for low light use.

I don't know if you have other MF lenses, but just in case- if you leave the camera set to AF-S, you will still get focus confirmation in the VF and the shutter will not release unless this happens, so you have the same protection against out-of-focus shots that you have with AF lenses. Good for catch-focus too.

[ChrisPlatt]

the biggest issue with the A version was the cheap build-quality of the aperture ring...

granted, if you leave it in the "A" position, it's a moot point...

There are many reports of aperture ring malfunction on the A50/1.7 lens.
Not so the M50/1.7 lens. Not sure how repairable this defect is today.

Chris

[mikesbike]

I just noticed, with some more recent camera models, which have a catch in focus selection in custom menus, this must be set to on before the shutter will not fire if a manual focus lens is not in focus.

---------- Post added 11-15-18 at 06:02 PM ----------

There are many reports of aperture ring malfunction on the A50/1.7 lens.
Not so the M50/1.7 lens. Not sure how repairable this defect is today.

Chris

I do not have the "A" version, just the "F" version which is an AF lens and also has the"A" setting on the ring. I've had it since it came on my new Pentax SF-1n I bought around 1990, my first AF camera. Never had any problem with mine.

However, even though the manual-focus "A" 50mm lens apparently has had malfunction of the ring, I wonder what specific malfunction? When these lenses were first released, the cameras being used did not have on-body aperture control. Even my SF-1n did not. The "A" position pertained only to the camera's "P" and "Tv" or shutter priority modes. For Av operation the aperture was set by the user via the ring. Same in the Manual mode. Oddly enough, the much later MZ-S went back to this kind of control arrangement So the ring was very often being rotated for user-set aperture, and therefore subject to wear vs.only rare use. It seems if it it is left on "A" ongoing with only occasional use for setting aperture, this should be a pretty stable situation, I would think.

Bottom line- how does the lens work now?

---

Last edited by mikesbike; 11-15-2018 at 06:13 PM.

[stevebrot]

There are many reports of aperture ring malfunction on the A50/1.7 lens.
Not so the M50/1.7 lens. Not sure how repairable this defect is today.

Chris

The instructions for repair are detailed in an article right here on Pentax Forums.

Pentax-A 50mm f1.7 Aperture ring repair - PentaxForums.com

However, even though the manual-focus "A" 50mm lens apparently has had malfunction of the ring, I wonder what specific malfunction?

The attachment point of a small metal spring comes undone. See link above for pictures and a detailed description.


Steve

[mikesbike]

I just put my olde "M" 135mm f/3.5 on my K-S2 and activated the catch in focus. Took a few test shots relying on the camera's AF confirmation and firing the shutter. Then I disengaged catch in focus, relied only on my own visual focus confirmation, disregarding the camera's confirmation, fired the shutter even without camera's confirmation, and found my own eye brought better focus.

---------- Post added 11-15-18 at 06:53 PM ----------

The instructions for repair are detailed in an article right here on Pentax Forums.

Pentax-A 50mm f1.7 Aperture ring repair - PentaxForums.com

The attachment point of a small metal spring comes undone. See link above for pictures and a detailed description.


Steve

Very useful info, Steve.

[Jim H]

Here's a question for all you A 50 1.7 owners. I've just put my (new to me) example on my K3 and its acting like it doesn't have an A setting on the aperture ring. "F--" in the aperture part of the display(s). Is there a contact on the lens that the camera isn't reading perhaps? I've changed the permit aperture ring use in the custom menu and can use the lens as if it were the M version but I'd like to be able to use the A functionality. Anyone ever had this happen?

[paulh]

You could try cleaning the lens and camera mount surfaces with a small bit of alcohol. Yes, there is an "A" contact on the lens that may not be getting a good connection with the camera.

[reh321]

Here's a question for all you A 50 1.7 owners. I've just put my (new to me) example on my K3 and its acting like it doesn't have an A setting on the aperture ring. "F--" in the aperture part of the display(s). Is there a contact on the lens that the camera isn't reading perhaps? I've changed the permit aperture ring use in the custom menu and can use the lens as if it were the M version but I'd like to be able to use the A functionality. Anyone ever had this happen?

Early in my days as a K-30 owner, I mounted the 'A 50 1.7' that was kitted with my beloved Super Program 32 years earlier. With the "A" setting it acted exactly as it should.

[Jim H]

You could try cleaning the lens and camera mount surfaces with a small bit of alcohol. Yes, there is an "A" contact on the lens that may not be getting a good connection with the camera.

Thanks for the reply. No luck with cleaning but measuring from the spring loaded lens location pin on the camera body I see that the third of the (seven total) lens contacts is slightly resessed unlike the others that are proud of the surface. It lines up with an indent on the lens which I guess is the "auto" contact. It doesn't move when the ring is rotated between auto and any other f stop so it looks Iike its stuck. I'm going to open it up following the instructions in one of the other posts. Wish me luck!

[stevebrot]

Here's a question for all you A 50 1.7 owners. I've just put my (new to me) example on my K3 and its acting like it doesn't have an A setting on the aperture ring. "F--" in the aperture part of the display(s). Is there a contact on the lens that the camera isn't reading perhaps? I've changed the permit aperture ring use in the custom menu and can use the lens as if it were the M version but I'd like to be able to use the A functionality. Anyone ever had this happen?

Is the aperture ring locked onto the "A" position? The "A" contact on the 50/1.7 is of the type that actually retracts into the mount when not set and locked on "A".


Steve

[swanlefitte]

non-compliant tele-converters (do any support KAF4?),

The da 1.4tc wr does.