Review on Tamron 17 50Mm Aspherical Pentax K Mount by Micha ochowski ᠌

The three lenses I tested for front and back focus on a target that is often used online revealed that autofocus behaves weirdly on all three of them, despite coming from separate batches. Here are the circumstances in which I became aware of it. 50–60 cm, Nikon D7000, as the goal. 50mm focal length, with an obviously wide open aperture. I disengage the focus on a faraway object, lock it on the target's central point, and then fire. All is as it should be if the lens is normal and does not have back focus. We nearly always obtain a steady back focus between 1 and 3 cm if we reduce the focus on a nearby object, for instance, by placing my palm in front of the lens, and then I concentrate back on the target. The stats are much more ominous if the lens also has rear focus. Likewise, when viewed from a broad angle. I brought a different D7000 in case it was the camera itself, but the situation was precisely the same! Perhaps there is an explanation for this behavior, but I was unable to locate it.