[snimcho]

Hello everyone,


I'd like to get an idea how often lenses fail because of electronics issues.
Normally this happens to AF lenses that are more than 10 years old but may happen with newer lenses also.

So if you have such lenses or if you know about such lenses please give some details.

Thanks

[interested_observer]

Good Morning,

That is somewhat of a loaded question. Let me explain in a couple of ways.

• In the past - up to a few years ago, Pentax had an AF - autofocus technology called SDM - "Supersonic Drive Motor". This technology in particular in the 16-50 lens, had a repetitively high failure rate. As of several years ago, Pentax figured out what was wrong and fixed it on future lenses. They also came out with a new AF motor called CM - which never had a problem.

Other than the AF motors, you have electronics that report the lens' settings. Electronics within the lenses (that support electronic interfaces) are really pretty robust. The original K lens, and M lenses have no electronic reporting capability. Starting with the A lenses type, the lenses that report.....

• identify the lens - i.e., Pentax A 50mm
• identify the aperture the lens is set to - i.e., f5.6
• identify the focal length which will vary on a zoom lens - i.e., 50mm if it's a zoom lens, then it will report the focal length that you zoom in or out to.
• identify the focus range - This will not report precise focusing distances, but will report in bands - close, far, etc.

[Bruce Clark]

I can report only one instance.

Sigma 70-200mm APO EX HSM Macro. Lens was new demo stock. Initial fault after 6 months was that AF completely failed. Returned to CR Kennedy, the Australian Distributors, who repaired it under warranty. Shortly after the AF failed again but only for subjects over 30 metres distant. Close up it was fine. CR Kennedy determined a faulty cct board in the lens to be the culprit and replaced the entire lens with another unit. No further problems have been experienced by me with this lens or any other.

[snimcho]

Good Morning,

That is somewhat of a loaded question. Let me explain in a couple of ways.

• In the past - up to a few years ago, Pentax had an AF - autofocus technology called SDM - "Supersonic Drive Motor". This technology in particular in the 16-50 lens, had a repetitively high failure rate. As of several years ago, Pentax figured out what was wrong and fixed it on future lenses. They also came out with a new AF motor called CM - which never had a problem.

Other than the AF motors, you have electronics that report the lens' settings. Electronics within the lenses (that support electronic interfaces) are really pretty robust. The original K lens, and M lenses have no electronic reporting capability. Starting with the A lenses type, the lenses that report.....

• identify the lens - i.e., Pentax A 50mm
• identify the aperture the lens is set to - i.e., f5.6
• identify the focal length which will vary on a zoom lens - i.e., 50mm if it's a zoom lens, then it will report the focal length that you zoom in or out to.
• identify the focus range - This will not report precise focusing distances, but will report in bands - close, far, etc.

Thanks for the answer. I actually mean any Pentax compatible AF lens. It can be Sigma or any other brand.

Normally the result of an electronics issue is: lens stops reporting settings to the camera. In result of that the camera can't AF with that lens anymore. Also for the minimum F number could be shown a wrong value.

The problem with old lenses is that no one offers parts for them. So no repairing possible. As there are many old AF compatible lense for Pentax I'd like to get an idea how often it happens. I already know about two Sigma lenses with dead electronics.

That thread is kind of addition to a thread which I started before:
https://www.pentaxforums.com/forums/189-repairs-warranty-service/324002-penta...-protocol.html
I already have some ideas how to go further but I still wonder should I dig more and spent more time on that issue...

Thanks for reading

---------- Post added 06-25-16 at 02:52 PM ----------

I can report only one instance.

Sigma 70-200mm APO EX HSM Macro. Lens was new demo stock. Initial fault after 6 months was that AF completely failed. Returned to CR Kennedy, the Australian Distributors, who repaired it under warranty. Shortly after the AF failed again but only for subjects over 30 metres distant. Close up it was fine. CR Kennedy determined a faulty cct board in the lens to be the culprit and replaced the entire lens with another unit. No further problems have been experienced by me with this lens or any other.

Thanks Bruce. In your case you got lucky because it has happened during the warranty period.
I don't have enough information for any conclusions but it seems that sigma have some weak points in their lens electronics or they just have sold more lenses than the other lens makers

[victormeldrew]

I think there is an issue identifying what is meant by 'failed electronics'.
Non-mechanical electronic components essentially live forever - they simply don't wear out. Quoted failure rates for integrated circuits and discreet components are in the order of 1's in millions and in reality are very much higher. Motors, if well designed, live shorter lives, but still can be very long-lived.

Failures are nearly always caused by damage. Water ingress (inadequate sealing), excess current or voltage (inadequate ESD protection), mechanical stress (inadequate mounting quality) and so on. Given a well-designed circuit and enclosure, this might never occur - the Voyager spacecraft being a perfect example...both still in full working order after nearly 40 years of operation in very tough conditions. But given that lenses are used and abused, to protect the components from this kind of damage requires a level of protection that is not considered financially worthwhile by the manufacturers...there is no incentive to make consumer products that last forever, particularly if that makes them 50% more expensive than their competitors.

[UncleVanya]

FA 80-320 is known to have a physical flaw that allows a small circuit board to break over time and render all lens communication null.

After that happens it is usable only when treated as if it were a big manual focus M style lens.

[stevebrot]

Starting with the A lenses type, the lenses that report.....

identify the lens - i.e., Pentax A 50mm
identify the aperture the lens is set to - i.e., f5.6
identify the focal length which will vary on a zoom lens - i.e., 50mm if it's a zoom lens, then it will report the focal length that you zoom in or out to.
identify the focus range - This will not report precise focusing distances, but will report in bands - close, far, etc.

I am being picky, but:

• None of the above is true of A-series lenses and one is not true of any K-mount lens
• A-series lack the "data" contact on the mount and are not (usually*) chipped with any electronics. The contacts provide max aperture, aperture range, and whether the aperture ring is in the "A" position and nothing else.**
• I believe you meant auto-focus lenses, all of which have an additional "data" contact and are capable of interacting with the camera body
• No K-mount lens reports the actual current set aperture. The only time the body "knows" the aperture setting is when the body sets it. It would be nice if the opposite were true, but unfortunately is not how it works. That is the essence of the so-called "crippled" mount. K-mount lenses with aperture rings have a mechanical coupler that may be used by the body to assess relative position of the ring for open-aperture metering purposes, but nothing more.

Steve

* A prominent exception is the Tamron PKA Adaptall-2 adapter which has a small logic board that allows the mount contacts to emulate the max aperture and aperture range of the Tamron line of lenses.

** The only real time logic is whether the aperture ring is in the "A" position and with some lenses, that is accomplished by physically retracting the "A" contact into the lens body.

---

Last edited by stevebrot; 06-25-2016 at 08:42 AM.

[stevebrot]

Non-mechanical electronic components essentially live forever - they simply don't wear out.

Yep!

FA 80-320 is known to have a physical flaw that allows a small circuit board to break over time and render all lens communication null.

...aye, and there's the rub. There are contacts* and flexible ribbon connectors as well as the circuit boards themselves that may fail over time with a resulting break in a critical circuit. In addition, hidden internal lens body damage may also render reporting features inoperable. It is not uncommon on this site to read things like, "I dropped my lens and everything is OK except that AF is confused...".


Steve

* Things like focus ring and zoom ring positions are communicated by physical contact points or rarely by inductive switches. If these become misaligned, corroded, or the wires broken one or more features will fail.

[Not a Number]

The new KAF4 lenses might report the aperture. More likely it will be a passive system and just respond to whatever the camera body says it should be set to.

With AF lenses the data pin seems to send lens ID, min-max apertures and focal length. In the case of zooms the focal length is in zones and there is info about variable max aperture. If you mount an AF lens on an MF A body (e.g. Super Program) or a non AF TC the passive "A" contacts are used - which only give min and max aperture info to the camera body without variable max aperture info. Some of the profile information appears to be in the camera firmware too.

AF zooms appear to use wiper or comb contacts to report the focal length. The comb can easily be damaged, as anyone that has taken a zoom apart can testify. The contacts can wear or oxidize or be knocked out of alignment.