Originally posted by pathdoc 1) What f/1.4 and f/1.8 autofocus lenses do you own, aside from this dreaded Sigma?
well, since you asked....
Pentax F 50mm f/1.7
Pentax F 50mm f/1.4
Pentax FA 50mm f/1.7
Pentax FA 50mm f/1.4
Pentax FA 31mm f/1.8 Limited
Pentax FA 77mm f/1.8 Limited
Pentax FA*85mm f/1.4
Sigma 24mm f/1.4 ART (Nikon F mount)
Sigma 35mm f/1.4 ART (Nikon F mount)
Sigma 50mm f/1.4 EX (Canon EF mount)
Sigma 50mm f/1.4 ART (Nikon F mount)
Sigma 85mm f/1.4 EX (Canon EF mount)
Canon EF 24mm f/1.4L
Canon EF 35mm f/1.4L
Canon EF 50mm f/1.0L
Canon EF 50mm f/1.2L
Canon EF 50mm f/1.4
Canon EF 50mm f/1.8
Canon EF 50mm f/1.8 II
Canon EF 85mm f/1.2L II
Canon EF 200mm f/1.8L
Nikkor AF-S 24mm f/1.4G
Nikkor AF 28mm f/1.4D
Nikkor AF-S 35mm f/1.4G
Nikkor AF 50mm f/1.4D
Nikkor AF-S 50mm f/1.4G
Nikkor AF 50mm f/1.8D
Nikkor AF-S 50mm f/1.8G
Nikkor AF-S 58mm f/1.4G (special)
Nikkor AF 85mm f/1.4D
Nikkor AF-S 85mm f/1.4G
Originally posted by pathdoc 2) Do you have any problems nailing focus with these on the camera(s) you've used the 18-35 Art on?
I still have issues with AF accuracy with this lens on my K5II Pentax K10D and loaned K3II bodies. Even with stringent AF calibration with the Lens dock*. My colleagues and students who also regularly use f/1.2~f/1.8 primes also have difficulties with AF accuracy with this particular lens on various Canon and Nikon camera bodies**. While AF inconsistencies are well known trade-off with faster lenses due to their inherently low contrast, which PDAF requires to be able to see the phase differential. The 18-35mm f/1.8 - with its high contrast even at f/1.8,
still manages to be by far the least accurate with PDAF even when compared to older AF lenses (like the Nikkor D series)
* In-camera AF calibrations with this lens are completely pointless.
** I don't know anyone who uses this lens on sigma cameras - sigma photographers generally seem to be rather quiet bunch. The AF module on Sigma cameras is similar to the K10D.