While the Sigma DG HSM Art lenses are outstanding, they are already large and heavy on a DSLR. On Sony mirrorless, they are even more awkward, because the rear lens barrel must be extended by 28.5mm to compensate for the DLSR mirror box gap.
Sony E: 18mm
Nikon F: 46.5mm
= 28.5mm extension required
This 28.5mm extension creates a torque arm(basic lever principle) that in my view raises the risk of damaging the lens mount sooner or later when used as I’d like to use a lens—hiking and such. Recent mountain hiking with several Sigma DG HSM Art lenses for Sony does not allay my fears; I constantly hold the lens to support it.
But even without this concern, the extension creates an unbalanced awkward feel. Functional yes, elegant no.
Below, the Sigma 85mm f/1.4 DG HSM Art for Sony E-mount can be seen with its 28.5mm extension versus the Sigma 85mm f/1.4 DG HSM Art for Nikon/Canon. This creates an increased lever arm torque which could damage the lens mount from impact, how much is unclear. It also has the effect of pushing nearly all of the weight of the lens well away from tyhe camera body, making for an unbalanced feel to camera plus lens.
Gary J writes:
Read your article with interest. Surprisingly little discussion of above problem elsewhere.
Bought Sigma 105 Art lens for Canon mount. Only camera that felt balanced with the 105 Art lens was the Canon 1DX2. However, had no OS or IS. Had problems handholding combo steady enough.
Just got the Sigma 105 Art lens for Sony E mount. Had the very problem you described. extension must result in additional torque and possible damage to A9. Supporting combo by holding lens. IBIS is helping greatly for better shots.
DIGLLOYD: I haven’t proven that it is a problem, but I can say this: as far as I’m concerned, it’s not viable to keep these lenses mounted on the A7R III while hiking as I do, at least not without carefully supporting the lens, which gets old.
While I did a lot of field shooting with the Sigma FE 14mm f/1.8 DG HSM Art, I was constantly supporting the lens as I hiked. That’s unacceptable for general use, and sometimes I need my hands, which means I then have to stop and stow it. That much mass and length is also unwieldy and I am certain that I would bang the lens into something before long. While the optical quality is outstanding, I just cannot see dealing with ergonomic factors. While Zeiss Otus lenses are large and heavy, they at least are matched to a larger camera body, and the weight is not pushed away from the camera so much.
The Sigma FE 135m f/1.4 DG HSM Art is even heavier, and even on a tripod it feels strained—I would never mount the camera to the tripod while sporting a 70-200/2.8 zoom, and the Sigma 135/1.4 feels like the same issue.