Sigma Announces Lens Compatibility Issues with K-1

Many recent lenses can potentially cause mount damage

By PF Staff in Third-Party Announcements on May 11, 2016

Sigma Japan has posted a product advisory warning customers that when select Sigma lenses are attached to the Pentax K-1, a minor scratch to the camera's lens mount may be inflicted. This notice applies to the following lenses:

Sigma advises customers to discontinue use of the affected lenses. The company plans to offer a repair service at a future date to address the issue.

In addition, Sigma states that the K-1 many not be able to correctly determine the correct image circle of Sigma lenses when the crop mode is set to "auto". Manual configuration of the crop setting is therefore recommended.

On an unrelated note, user reports suggest that certain older Sigma lenses cause the K-1 to freeze after being mounted— including the 70-200mm F2.8 EX DG APO Macro HSM II. A firmware update for the affected lens(es) may be necessary to rectify this issue.

How the K-1 Mount Differs

While the Sigma press release does not explicitly describe the nature of the potential damage to the camera, a likely scenario is that the area directly above the lens mount gets scratched. The K-1's larger prism housing protrudes farther beyond the lens mount than other Pentax bodies and it is also angled more steeply, which could lead to scrapes while mounting lenses designed without this in mind.

We can only speculate whether this issue is related to improper mount implementation (reverse-engineering) by Sigma, or an internal change to Pentax's own mount specifications.

To date we do not know of any incompatibilities or issues with genuine Pentax lenses and the K-1.

Speaking of other mount differences, the K-1's focusing screen foam is situated much closer to the edge of the bayonet mount compared to Pentax APS-C bodies. This foam spans the entire width of the mirror, rather than having a gap in the middle as on film SLRs such as the MZ-S. The retaining clip for the focusing screen is also more exposed than on other Pentax bodies. These differences don't seem to be causing any issues, however— nor should they.

K-3 Mount (left) vs K-1 Mount (right)

Press Release