DA 12-24mm vs Sigma and Tamron 10-24mm Comparison
Sigma and Tamron offer internal micro motors for Nikon and Canon mounts but rely on the camera's internal screw-drive in the Pentax and Sony mounts. One possible reason for this is that the older Pentax cameras did not have the ability to power the lens. Given that all three lenses have internal focusing driven by camera’s screw drive, the autofocus results should be similar across the board. For this section we will examine the relative speed of the autofocus capability of the three lenses. Each lens was timed for its response time from minimum focus distance to infinity and infinity to minimum focus distance. The test was completed three times and the times were averaged to minimize errors. The results were then charted as seen below.
The response time for all three lenses was less than one second, which is very impressive. The test was completed in daylight with a Pentax K-5 on a tripod with an electronic timer that measures in fractions of a second. Of course, your individual response times might vary depending on ambient lighting and subject matter.