Sigma 17-70 aperture problem on K-5

[Denisio Fabuloso]

I use a Sigma 17-70 on my K-5. I have noticed I am no longer able to access full open F2.8 anymore. The lens itself doesn't seem to have any obvious mechanical issues like sticky blades. I suspect its more like something to do with the electrical connections, but cleaning all the points provided no solution either. Anyone have any ideas what could be going on? All my other lenses work perfectly well. I recently installed the V1.14 firmware upgrade. Surely it wouldn't be that. Thanks.

 

[Benoz]

Denisio Fabuloso wrote:

I use a Sigma 17-70 on my K-5. I have noticed I am no longer able to access full open F2.8 anymore. The lens itself doesn't seem to have any obvious mechanical issues like sticky blades. I suspect its more like something to do with the electrical connections, but cleaning all the points provided no solution either. Anyone have any ideas what could be going on? All my other lenses work perfectly well. I recently installed the V1.14 firmware upgrade. Surely it wouldn't be that. Thanks.

I too upgraded to FW 1.14 recently and have no problem with my 17-70 in setting at F2.8.

Have no idea what could be the problem with yours! Sorry can't help.

 

[markusm]

Denisio Fabuloso wrote:

I use a Sigma 17-70 on my K-5. I have noticed I am no longer able to access full open F2.8 anymore. The lens itself doesn't seem to have any obvious mechanical issues like sticky blades. I suspect its more like something to do with the electrical connections, but cleaning all the points provided no solution either. Anyone have any ideas what could be going on? All my other lenses work perfectly well. I recently installed the V1.14 firmware upgrade. Surely it wouldn't be that. Thanks.

Indeed, sticky blades would cause problems with narrower apertures, not wider apertures. As the lens should be wide open for metering, if you experience any underexposure problems, it's a weird problem. The aperture shouldn't depend on any electrical contacts but only on that little lever sticking out of the mount.

I can't think of anything that would cause only this single lens to be wide open for metering and then close down for the exposure.

What are the symptoms, by the way?




Markus

 

[Jim in Hudson]

Denisio Fabuloso wrote:

I use a Sigma 17-70 on my K-5. I have noticed I am no longer able to access full open F2.8 anymore. The lens itself doesn't seem to have any obvious mechanical issues like sticky blades. I suspect its more like something to do with the electrical connections, but cleaning all the points provided no solution either. Anyone have any ideas what could be going on? All my other lenses work perfectly well. I recently installed the V1.14 firmware upgrade. Surely it wouldn't be that. Thanks.

Can you tell if just mounting the lens is causing the aperture blades to close a little? If you have enough light coming through the back of the viewfinder you might be able to see this looking through the front of the lens.

 

[DrewE]

Do you mean that the camera doesn't think it's an f/2.8 lens, or that the camera claims f/2.8 but the lens isn't actually wide open?

If it's the former problem (the camera misreads the lens information), the problem is something related to the contacts on the lens mount. Try re-cleaning them on the camera and on the lens.

If it's the latter problem, there's some mechanical difficulty or misadjustment, or sticking of the iris mechanism in the lens, or something along those lines. Possibly the little lever that actuates the diaphragm got a bit bent. Testing with other lenses and camera bodies should help determine if the lens or the camera is at fault.

If the lens had an aperture ring, it would also be good to verify that it's fully in the 'A' position. It seems from the pictures I can find online that this lens doesn't have an aperture ring, though.

--

--DrewE

 

[KentG]

Considering the occasional system gliches with new camera models caused by Sigma having to reverse engineer the electronics anything is possible.
I suggest putting the lens on an older body to see if it has the problem. If is does it is some kind of problem in the lens. If it does not it means the lens likely needs a firmware update from Sigma. Contact Sigma on that.

Kent Gittings

 

[EArenz]

Benoz wrote:

Denisio Fabuloso wrote:

I use a Sigma 17-70 on my K-5. I have noticed I am no longer able to access full open F2.8 anymore. The lens itself doesn't seem to have any obvious mechanical issues like sticky blades. I suspect its more like something to do with the electrical connections, but cleaning all the points provided no solution either. Anyone have any ideas what could be going on? All my other lenses work perfectly well. I recently installed the V1.14 firmware upgrade. Surely it wouldn't be that. Thanks.

I too upgraded to FW 1.14 recently and have no problem with my 17-70 in setting at F2.8.

Have no idea what could be the problem with yours! Sorry can't help.

Checked out my Sigma 17-70mm f2.8-4.5 and it goes to f2.8 and stays there until about 22mm where it switches to f3.5, then switches to f4 at about 35mm and finally f4.5 at around 64mm. K-01 with v1.02 FW.

Ed

 

[Denisio Fabuloso]

Thanks for feedback. I have tried uber cleaning of contacts on lenses and cameras. Tried other lenses on K-5 and and they work fine. Have tried the 17-70 on my older K-20... but still no cigar - simply cannot access F2.8 at ANY focal length. Beats me. BTW... there actually is firmware applications for lenses?

 

[markusm]

Denisio Fabuloso wrote:

Thanks for feedback. I have tried uber cleaning of contacts on lenses and cameras. Tried other lenses on K-5 and and they work fine. Have tried the 17-70 on my older K-20... but still no cigar - simply cannot access F2.8 at ANY focal length. Beats me. BTW... there actually is firmware applications for lenses?

Can you detail what exactly doesn't work? As I asked before, what precisely are the symptoms that you see?

 

[Denisio Fabuloso]

I dont see any problems as such... only the F4 indicator thru the viewfinder when on full open at 17mm. I tried shutter speeds that took the exposure will into under exp. Also tried every mode available on the camera. Simply cannot access the 2.8 aperture on the camera with this lens. Sigma Australia (CR Kennedy) will look at the camera but it will cost a minimum of $120 plus postage. Seems expensive way to buy a stop. The lens cost about $550 a few years ago. Pretty disappointing. I have lenses at home over 40 years old still going strong... both primes and other.

 

[BrianA2]

I have this lens, and on my K200d "Auto" mode would never use f2.8. "P" mode would use it when necessary.

I do not notice the same problem on my K-r.

Brian

 

[DrewE]

When you operate the optical DOF preview with the camera claiming f/4, does the viewfinder image dim?

If it does dim, the camera knows that the lens is an f/2.8 lens, and is for some reason not letting you select that aperture. (Maybe you've unwittingly activated exposure bracketing mode?)

If it does not dim, the camera thinks that the lens is an f/4 lens, indicating something wrong with the electrical communications between the camera and the lens. Since the camera works fine with other lenses, it would seem to be a faulty lens, though this is not 100% certain.

 

[awaldram]

Denisio Fabuloso wrote:

I dont see any problems as such... only the F4 indicator thru the viewfinder when on full open at 17mm. I tried shutter speeds that took the exposure will into under exp. Also tried every mode available on the camera. Simply cannot access the 2.8 aperture on the camera with this lens. Sigma Australia (CR Kennedy) will look at the camera but it will cost a minimum of $120 plus postage. Seems expensive way to buy a stop. The lens cost about $550 a few years ago. Pretty disappointing. I have lenses at home over 40 years old still going strong... both primes and other.

sound like your in 'P' or 'Auto' and have program line set to MTF

what happens in Manual can you select f2.8 with the lens at its widest (17mm)

or

Tv select f2.8 can you??

 

[hanhait]

I have the K-5 + Sigma 17-70 2.8 - 4.5 (not the newer 2.8-4.0). I upgraded the firmware and I do not have the problem you have. If your camera still exposes correctly you may consider to leave things like that: the lens is at its worst at 17 mm - 2.8 and in fact I wish I could automatically limit it to f/4 to have reasonable sharp images at 17 mm.

 

[Denisio Fabuloso]

Thanks for the input. All feedback gratefully received. Can get 2.8 in any mode at 17mm. Not sure what you mean by MTF in program mode? Cant find any ref in the manual. Can you elaborate? Thanks.

 

[Denisio Fabuloso]

DrewE, I tried the aperture preview and from F4 it doesnt drop back at all in the finder. All the other apertures work as expected. Suggests that something in the lens is just not working. Either some electrical connection issue or the notch on the lens that alters the aperture is faulty in some way. Tho thru the back of lens it seems to be opening fully and seems perfectly aok ... but who knows. I know its only a stop... but its why I bought it over the Pentax version. I also changed lens options in the program line and played with a few of them... but no avail. This one has really got me beat.

 

[Denisio Fabuloso]

Oh... now I know what you mean. I played with all the lens options in P line and none of those gave me a F2.8 unfortunately. But a good suggestion never the less.

 

[Denisio Fabuloso]

I like to have that extra stop as an option never the less. No problem to stop down to F4 - plenty options there. I prefer that its me making the decisions rather than the lens... but I take your point. Thanks for taking the time.

 

[DrewE]

Denisio Fabuloso wrote:

DrewE, I tried the aperture preview and from F4 it doesnt drop back at all in the finder. All the other apertures work as expected. Suggests that something in the lens is just not working. Either some electrical connection issue or the notch on the lens that alters the aperture is faulty in some way. Tho thru the back of lens it seems to be opening fully and seems perfectly aok ... but who knows. I know its only a stop... but its why I bought it over the Pentax version. I also changed lens options in the program line and played with a few of them... but no avail. This one has really got me beat.

If it's not getting any darker in the finder, that indicates that the lens is actually at f/2.8 but the camera mistakenly thinks the f/2.8 is f/4.

On the Pentax mount, the narrowest aperture setting and the number of stops of aperture range (from which the widest aperture setting can be figured) are encoded by the presence or absence of continuity at several of the contacts on the lens mount. It seems as though one (or more) of those contacts is being misread for some reason.

If you're curious, a good description of these contacts is at http://kmp.bdimitrov.de/technology/K-mount/Ka.html

 

[Denisio Fabuloso]

Excellent information, explanation and links... gentleman and a scholar for sure! Will follow up the link you provided and see if I cant fix this annoying malfunc. Thank you for the heads up.

Denisio