[mloiselle]

Early in 2008 I purchased a Pentax K10D body and Sigma 24-70 F2.8 EX DG and Sigma 100-300 F4 APO DG EX (SN 5022926) lenses. Both lenses coupled and worked flawlessly with the K10D body.

Late last year I upgraded my camera body to a Pentax K-5.

The 24-70 F2.8 lens works as before, but the 100-300 F4 lens has problems with an intermittent
connection to the body. At times the camera display shows "F--" for the f-stop. The auto focus
no longer works and the lens will not close down. I believe the problem has become more common
over the past few months.

The problem appears to be with the mounting hardware on the 100-300 F4 lens, but C.R.I.S. is telling me this version of the 100-300 is actually not compatible with the K-5. Something to do with a ROM based motor (person I spoke to was relaying information from a tech). I find this hard to believe given the fact that the lens works perfectly much of the time, I can generate the problem by torquing the lens slightly, and I've seen a number of posts here and elsewhere extolling the virtues of the lens.

So, is C.R.I.S. correct or blowing smoke? If the latter, can anyone suggest a solution to the intermittent contact problem?

I've removed the mount plate and looked at the contact unit, but don't know what I might do to tighten the lens fit or improve the electrical connection to the body.

Thanks for any help.

Marc Loiselle

[bdery]

I would suggest contacting Sigma. If the lens is not compatible as is, there should be a way for them to update the firmware of the lens, or even change the chip. They do that for flashes.

[civiletti]

I suggest selling me that lens really cheap.

[Adam]

I don't think they know what they're talking about- worst-case, you can always stop-down meter, after all. All K-mount lenses work with the K-5

With that said, I hope you're able to fix the lens to regain full AF and AE capabilities!

Adam
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[koper]

you have to chek if the lens work good with Pentax K10D
i think that the problem is the contact between the camera botton and the lenses

in repair unit they elevate a bit the botton

[Erd§]

but C.R.I.S. is telling me this version of the 100-300 is actually not compatible with the K-5

Absolute nonsense. I have the same version and I've never had an issue with mine...and everything works as it should. Everything.
If a lens is known to be incompatible with a body, then the problem wouldn't be intermittent. How can something be incompatible...but only sometimes?
I would look into the contacts...either on the body or the lens.

[Digitalis]

I got my Sigma 100-300mm APO EX DG in 2008 (S/N 5024927) and I have experienced an occasional display of the F-- indicator issue when used with my K10 and K7 cameras. I do have a theory on why your lens may be experiencing problems:



I some time ago I had to repair the mount lock on the lens mount because after years of (ab)use the locking pin had actually caused some wear on the lens mount. This was causing problems with the information pins and AF connection becoming misaligned, also make sure the lens mount on both the camera body and the lens itself are clean.

I too share your scepticism over the lens incompatibility with the Pentax K5 statement...if there was actually an incompatibility issue then I think that there would be far more complaints made about it. The Sigma 100-300mm f/4 APO EX DG is one of my favourite lenses on the K5IIs



PS. every time I hear about issues like this It reminds me of this scenario:

A Software Engineer, a Hardware Engineer and a Departmental Manager were on their way to a meeting in Switzerland. They were driving down a steep mountain road when suddenly the brakes on their car failed. The car careened almost out of control down the road, bouncing off the crash barriers, until it miraculously ground to a halt, scraping along the mountainside.

The car's occupants, shaken but unhurt, now had a problem: they were stuck halfway down a mountain in a car with no brakes. What were they to do?

"I know", said the Departmental Manager, "Let's have a meeting, propose a Vision, formulate a Mission Statement, define some Goals, and by a process of Continuous Improvement find a solution to the Critical Problems, and we can be on our way."

"No, no", said the Hardware Engineer, "That will take far too long, and besides, that method has never worked before. I've got my Swiss Army knife with me, and in no time at all I can strip down the car's braking system, isolate the fault, fix it, and we can be on our way."

"Well", said the Software Engineer, "Before we do anything, I think we should push the car back up the road and see if it happens again."

---

Last edited by Digitalis; 03-20-2013 at 01:08 AM.

[stormtech]

I would suggest contacting Sigma. If the lens is not compatible as is, there should be a way for them to update the firmware of the lens, or even change the chip. They do that for flashes.

While CRIS is an authorized service center for Sigma, I would be inclined to send it to Sigma service in Long Island NY. I've had nothing but great success with them included updating lens firmware if need be.

Service & Support | Sigma

It is the one in Ronkonkoma, NY

[koper]

this probelms happens with havy lenses
i had the same problem wit sigma 170-500 mm
there is to fix the contact on the lenses and the camera

[AdrianM]

It sounds like you may have a problem with either the lens or the camera body electrical connections. I have the Sigma 100-300 f4 and it is a lens I do not have any troubles with on K10D, K20D and K5, but I have found my K5 to be problematic with some lenses losing connection just as you have described. The solution is a good clean of the pins - I use a wooden toothpick to make sure that the pins move freely and to clean off any tarnishing on the surface (and the wood is too soft to damage anything).

[tram57]

I have the 100-300 F4 apo and it works fine with the k5. It has screw drive unlike the canon and nikon versions. Must be something wrong with your lens or camera mount.

[HanSch]

A few months ago I bought a used Sigma 4/100-300 EX DG. The autofocus is very consistent and repeatable, but there is a small back focus.
The K5 stores the AF adjustments and the lens is recognized, but the combination doesn't respond to the adjustments. I can set the max. adjustments of -10 or +10 with no result.
I tried to bypass the problem by setting a correction for all lenses (I can switch it off when using one of my Pentax lenses), but the result is the same: no adjustment.
No problem with corrections for other lens/camera combinations. I have a rarely used Sigma 28-135 IF that can be corrected nicely, Pentax lenses no problems either.

I didn't clean the contacts so far, but they are clean. Anyone with a solution?

[dadipentak]

I would be inclined to send it to Sigma service in Long Island NY. I've had nothing but great success with them included updating lens firmware if need be.

I'll second that--I've had very good experience with them.

[felixkh]

A user in the Singapore forum has the same lens and it works with his K5.

[Edgar_in_Indy]

I'm not at home, and I can't remember if my 100-300 has an aperture ring, but if it does, you should make sure it has not moved off of the camera control of aperture setting. Although that should not effect AF, but still something to check...

I've had this problem occasionally with different lenses on my K-30, but it's not common. The lenses that seems to be most prone to it are my Sigma 30mm 1.4 and Tamron 28-75mm f/2.8, but maybe I just have that impression because those are the lenses I switch on and off the most. Any time it does happen to me, I can just release and remount the lens to fix it.

It seems like other people have the problem most commonly with bigger, heavier lenses, perhaps because the weight of the lens hanging off the mount creates a slight gap.

I would echo the other people who have had excellent experience with Sigma. I have sent lenses to their NY headquarters a few times, and they have always been very fast and very competent, and whenever there were charges they were reasonable.