Pentax-DA* 50-135mm F2.8 Review
Vignetting
Vignetting is the decrease of brightness in the corners or periphery of an image. For this test, an image was taken at the various focal lengths of the Pentax-DA* 50-135mm F2.8, at its widest apertures. Since vignetting increases with aperture, this test will provide the worst-case scenario results for this lens.
| F2.8 | F4 | F5.6 | |
| 50mm |  |  |  |
| 63mm |  |  |  |
| 75mm |  |  |  |
| 95mm |  |  |  |
| 135mm |  |  |  |
Click on any thumbnail for a larger photo.
We analyze the above pictures by comparing the average pixel values of the center and the corners. When expressing the corner/center values as a percentage, the results are the following (higher is better):
Average Pixel Values | F2.8 | F4 | F5.6 |
| 50mm | 85% | 94% | 98% |
| 63mm | 84% | 93% | 96% |
| 75mm | 81% | 90% | 94% |
| 95mm | 80% | 88% | 93% |
| 135mm | 79% | 86% | 92% |
Vignetting Verdict
Vignetting is minimal but present at all focal lengths at F2.8 and F4, and worsens slightly as you zoom in. At F5.6 there is only slight vignetting at the longer focal lengths. In practice, this can easily be corrected during post-processing, and it will likely go unnoticed in most scenarios, even when left uncorrected. Overall, the 50-135mm could have done better in this respect, but we find this degree of vignetting to be acceptable considering the fact that this is an APS-C lens.
