Depending on how much glass you've invested in, switching to a different SLR system can be a daunting task. A longtime Canon shooter who wants to explore the Nikon side of the fence will be faced with the prospect of selling cameras and lenses on the used market, likely at a loss, and purchasing similar lenses all over again in a different mount. It's enough to keep shooters locked into a camera system for years, even if they've become dissatisfied with some of its aspects.

Today Sigma announced a new service to change the mounts on its lenses, but it's not a universal cure for system switchers. Only newer lenses that are part of the company's Global Vision line—which includes categories for Sport, Contemporary, and Art lenses—are able to be converted, and they can only be converted to a lens mount in which they are available at retail. The cost of conversion ranges from $80 to $250, depending on the lens, and doesn't include shipping costs; but it does add a six-month warranty to the lens.

The list of lenses that are eligible for this service is fairly short. It includes the 120-300m F2.8 DG OS Sport and the 35mm F1.4 DG Art for full-frame cameras. APS-C lenses covered are the 30mm F1.4 DC HSM Art, the 17-70mm F2.8-4 DC OS Macro Contemporary, and the 18-35mm F1.8 DC Art. A few mirrorless lenses can be changed from Micro Four Thirds to Sony E-mount or vice versa; these include the 19mm F2.8 DN Art, 30mm F2.8 DN Art, and the 60mm F2.8 DN Art.

The conversion service is a bit limited to start, but going forward new Sigma lenses will be eligible. It's likely not enough to make switching systems an easy task, but it's a step in the right direction. The most recent Sigma lenses that we've reviewed have been quite impressive performers; both the 35mm F1.4 DG Art and the 18-35mm F1.8 DC Art earned our Editors' Choice award.

Sigma also announced that all lenses, flashes, and cameras purchased on or after July 1 are now covered by a four-year warranty. Previously, warranties varied from product to product.