DA* 16-50mm vs. Sigma and Tamron 17-50mm F2.8 Comparison

Sigma: Optical Stabilization

As we've already mentioned, the Sigma 17-50mm f/2.8 OS lens uses an in-lens Optical Stabilization system. On Pentax bodies, this system can be used in place of the in-body Shake Reduction system, but it is not recommended to use the two systems at the same time.

For this test, we shot 30 exposures each with SR on, OS on, and neither on, in batches of 10. All 90 shots were taken at a shutter speed of 1/5 of a second—a speed that is almost certain to cause significant motion blur in the absence of some kind of stabilization. We marked each exposure as a hit (no motion blur), near miss (slight motion blur), or miss (significant motion blur). We then tallied them all up and derived percentages for each category. 

Test Results

Conclusions

Based on our testing we found no statistically significant difference between the in-lens and in-body stabilization systems. We conclude that both systems produce a very good keeper rate, even at very slow shutter speeds, while turning both off resulted in a dramatically lowered 13.3% keeper rate over 30 test exposures.

Based on these findings, we do not feel that the Sigma lens's OS system is a significant selling point when used on a Pentax body. Moreover, we feel that (based on our observations in shooting the tests) maintaining a good posture, steady breathing, and good shooting technique have a far greater effect on the keeper rate than do the different varieties of stabilization systems.