[Dan K] had just such a lens from Sigma, but wanted to get it working fully with a camera using the Canon EF lens fitting. Hacking ensued. The lens in question was a Sigma 15-30mm f/3.5-4.5 EX DG ...

The 16mm F1.4 lens is the largest prime lens of the bunch, with the widest perspective, equivalent to 24mm. It measures 90.3mm in length and weighs 14.6oz / 415g, while its perspective is similar to ...

A short telephoto focal length, combined with a large maximum aperture and fast autofocus speed, make the EF 85mm f/1.8 USM an ideal optic for any photographer shooting portraiture.

But when [Loudifier] needed an extension tube to do extreme close-ups with a wide-angle lens on a Canon EF-M camera, it needed to be small…really small. The final 3D printed extension provides ...