[Caat]

Hey Guys

Has anyone had any experience of Sigma's lens alteration service for the K1? - where they change the mount slightly to avoid the mount scratching issue.

I was wondering how people have found the service, how long did it take, what did Sigma actually do etc.

I am also interested to know if they do it for second hand lenses (ie ones outside of warranty) and what the charge might be. However, I can email them myself to find out that information.

Cheers!

Charley

[clackers]

I was able to pick it up within a week of dropping off, here in Melbourne (home of the Sigma importer).

[Paul the Sunman]

Very quick and easy. A few days at CR Kennedy in Melbourne and my 35mm f/1.4 Art was ready to go. The change is quite apparent; the metal mount plate is replaced by one with a bevel. It's that simple. Definitely recommended.

[beholder3]

It happens quickly.

But due to Sigmas feared low quality standards, you might run into follow up issues again:
https://www.pentaxforums.com/forums/190-pentax-k-1/319686-k-1-3rd-party-lens-...bility-12.html

Exchanging the mount inevitably means you might see an effect on AF finetuning since sloppy quality control on mount thickness will immediately throw off your prior settings. And that what seems to happen sometimes

They changed my mount what I asked them NOT to do.
All for free.
Because of that I have problem with autofocusing now.
Adjustment is on -10 and autofocus is not good enough.
At least it works now but it will need another servicing..

[edin_togger]

Sigma UK advised roughly a week, but also confirmed that new stock should be already fixed.

I've got one coming today so I'm hoping it's had the new bit added already.

[rawr]

I am also interested to know if they do it for second hand lenses (ie ones outside of warranty) and what the charge might be.

Second hand & out of warranty lenses seem no problem (as long as the lens is on the list of known problem lenses). No charge for the service.

[philanker2012]

Sigma UK turned round my 85mm f1.4 in less than a week, free of charge.If you have any concerns they are quite approachable and will carry out the mod on any lens they have identified that needs it. Second hand is not a concern. Best to speak to them first via their contact page and they will give you a reference number before you return the lens.

The same modification is required for K70,although on their despatch note they list it as K1 modification. The note also says that they have : reset, check and test.
No problems with my lens since it has been done.

[stevebrot]

It happens quickly.

But due to Sigmas feared low quality standards, you might run into follow up issues again:
https://www.pentaxforums.com/forums/190-pentax-k-1/319686-k-1-3rd-party-lens-...bility-12.html

Exchanging the mount inevitably means you might see an effect on AF finetuning since sloppy quality control on mount thickness will immediately throw off your prior settings. And that what seems to happen sometimes

Given that user banep has no smoking gun on this matter except that Sigma performed a free upgrade hardware/firmware service on his Sigma 70-200 HSM II,* I would suggest that this comment is sort of spreading an unverified rumor of general low quality standards related to the mount swap. It should be noted that before the service, the lens would cause complete lock-up of the K-1 and it is not clear whether AF fine adjust was even possible before the free firmware upgrade it was sent in for. Granted, there may have been problems associated with the service, but lay the blame on whoever does Sigma service for Slovenia and not the company as a whole.


Steve

* Model was retired by Sigma in 2010

[Unregistered User 8]

Sigma K1 Lens Alteration

Hi Charley. @Tau-Ceti did a review of the Sigma 35mm 1.4 art and included these images. Hope it helps.

[rawr]

his Sigma 70-200 HSM II,

FWIW, after the mount-swap, my Sigma 70-200 HSM II autofocus needed no adjustment. Just did a quick check to confirm!

I guess a slight thickening of the mount ring post-swap could indeed impact AF calibration, but as the lens still has to bayonet quite tightly into the body, the distance between the lens rear element and the AF module would not be able to alter much. After all, the placement or dimensions of the bayonet lugs is not altered by the mount ring swap.

[stevebrot]

I guess a slight thickening of the mount ring post-swap could indeed impact AF calibration

Should not make any difference. PDAF is is not affected by lens registration distance* and fine tuning (both global and per lens) makes no physical changes to the system. I would be more concerned about retention of infinity focus post mount swap. It has been my understanding that front/back focus as it relates to PDAF is caused by asymmetry of the image at the detector resulting from optical aberration and/or decentering. Fine tuning applies an offset to the processed detector output.


Steve

* This is probably best shown by using manual focus confirm and a thin close-up extension tube.

[Tako Kichi]

This thread caught my eye as I recently acquired a K-70 and some people had been reporting issues with that having collisions as well as the K-1. I thought I'd better check the fit on my one and only Sigma lens and I'm happy to report that the 105mm EX DG Macro does not appear to have the issue. Yes it's a tight fit but there is a small air gap between the mount and the underside of the flash housing. I will make sure I am extra careful when using it though as there is little room for error when aligning the mounts.

I am guessing that the problem only happens on specific Sigma lenses, anyone have a definitive list of the offenders?

EDIT: I just found this list on the Sigma website: https://www.sigmaphoto.com/article/use-of-pentax-mount-sigma-lens-with-pentax-k1/