[m4ciekk]

Hi everyone,

I bought Sigma 10-20 F4-5.6 EX DC lens this week for my K5. It was a used copy but the seller told me it's in perfect condition and worked well with his K7 and K3 and he also had no problems with autofocus at all. Today I unpacked the package, attached lens to my K5 and ... the focal range appears. The same I see when I attach a manual lens. After confirming / canceling the focal length, the MF icon appears on the LCD screen, even though the focus mode lever is set to AF.C or AF.S mode. There is no F-- on the screen but I can not really control the aperture, because it shows me some incorrect values such as F1.2.

First thought – I bought a broken lens, but out of curiosity I've attached it to my old body – K100D and you won't belive. Autofocus as well as aperture works with it. The lens seems fine with K100D.

My other AF lenses such as Sigma 17-50 F2.8 EX DC HSM, Pentax-F 50 F1.7, Pentax-F 70-210 F4-5.6 and Pentax-DA 35 F2.8 Ltd works well with my K5. I have no problems with them at all. The body recognize all of them.

K5 firmware is up to date. 1.16 version.

I exclude dirty contact pins in K5 bayonet, since AF works in lenses I mentioned above. I also have to exclude dirty pins in Sigma 10-20 bayonet since it works correctly with K100D.

So what can be the reason that this Sigma does not work with my Pentax K5body?

Someone told me I have to send this lens to Sigma authorized repair distributor and they should update the lens software. It's strange a bit because K5 is older than K3 so if it worked on newer model, so why it doesn't work on the older one? What do you think about that guys? Does anyone of you had the same problems with Sigma lenses?

Cheers,
Maciek

[pepperberry farm]

Welcome to PF!



I have heard/read some incompatibilities between some Sigma lenses and some bodies...

how about the firmware in your K-5; is it up-to-date?

[Not a Number]

I wouldn't exclude dirty contacts. It takes so little effort to clean them what do you have to lose by trying?

The compatibility database lists this lens and K-5 as fully compatible. Can the lens firmware be updated with the docking port? Try seeing if there is an update for the lens.

[m4ciekk]

Welcome to PF!



I have heard/read some incompatibilities between some Sigma lenses and some bodies...

how about the firmware in your K-5; is it up-to-date?

@pepperberry farm
Thanks

Yes, the firmware in K5 it's up to date. I thought maybe downgrade would help but I have no idea where should I look for an older version of it. It's really strange that this lens works well with my old Pentax K100D. The camera which I stopped using long time ago and I hid deep in the box and almost forgot about it.

@Not a Number
I already cleaned both contact pins (in camera and lens too) using Isopropyl alcohol twice with no effects. If the lens work with older camera and the rest of my lenses work well with K5 it should not be the problem with contact pins. Although maybe you are right. Maybe I should use sth else to clean that.

I have no idea how to check lens firmware in home conditions. It's too old I belive. Sigma's USB dock is not compatibile with this lens.

It seems I have to wait for the reply from Sigma authorized repair distributor and I hope they could solve the problem... or I will have to buy a new body which I would like to avoid for now

[rod_grant]

I have that lens and it worked fine on my K-5 (when I had the K-5).
I was on FW v 1.03. Metadata shows all settings were recorded correctly, except the lens is listed as "Tamron or Sigma Lens", (which is not unusual!!)
Good luck getting a solution: I have found it's a bit of fun playing with that focal length.

[marcusBMG]

I can corroborate that my example of this lens worked fine on my k5, and is fine on my K3. But I can also add that a sigma 18-125 that I sold had to be returned because of same issue you have - wouldn't connect with purchasers K10D.

[beachboy2]

I wonder if the AF adjustment is too far out of range for your camera. For instance, the K5 may be at one extreme and the 10-20 at the other. Try adjusting the lens focus correction within the K5 to the extremes. eg +10 and try. Then -10 and try. I remember that a number of owners had to adjust the front or back focus for this model of lens to a substantial number and in some case get the lens/camera combo adjusted. Mine has a significant adjustment (+6?).

[photocles]

I have a similar issue with my K-5 and my Sigma 18-300. Every once in a while it just doesn't seem to "line up" with the contacts correctly and everything stops working as it should. If I simply rotate the lens (like 4 mm) and return it to lock, it's fine again until it isn't. This doesn't happen with the 18-300 on any of my other bodies. Weird.

[marcusBMG]

Yes, certainly try lots of wiggling, taking the lens on and off, cleaning and manipulating the contacts.
I had a PKA sigma 28mm that initiially was intermittant connection in "A", with use and manipulation the intermittance disappeared.

[m4ciekk]

Ok guys, I'm back!

Two weeks ago I sent my Pentax K5 with Sigma 10-20 F4-5.6 to the Sigma authorized repair distributor in my country.

A few days later I received the diagnosis: "The lens had the latest version of the software. Lack of communication with the Pentax K5 is caused by a break in the ground circuit of the camera bayonet and a twisted bayonet. In fact, 1.5 years ago the camera mounted to the tripod fell on the ground and the bayonet was pull out of the body, but I fixed it and everything worked as before.

They asked for 80 USD, which was the 40% of the amount I paid for the lens. I refused because it was too much for an old lens in my opinion which still works, but not with my K5. I started thinking about buying a new body such as K3 II/ KP... or even Sony A6300 but I decided to wait.

And now the best part! Last week I got my camera back. Out of curiosity, I have attached the Sigma 10-20 to the K5, turn on the camera and ... AF worked. I couldn't believe so I unmounted the lens, mounted it again, turned it on and it showed me AF.C again. I changed the modes, did couple of test shots and it worked as my other lenses. Each time the camera recognizes the lens and AF works. I have no idea what happend.

My total cost of this repair was less than 4 USD - shipping cost.

Thanks to all for your help!

Cheers,
Maciek