Pentax-D FA 100mm F2.8 WR Macro Review
Sharpness and bokeh can be subjectively evaluated in the images in the drop down menu below. These images were shot on a tripod with shake reduction disabled at ISO 200 in RAW with a K-5. They were converted by Adobe Camera Raw with no changes in image parameters, then smart sharpened slightly (amount 125, radius 1) in Photoshop CS5, and cropped (maintaining resolution). We selected a cactus as our test subject due to the busy background which really challenges the lens's bokeh characteristics. We had no doubt that sharpness would be top notch since we have used the older Pentax 100mm Macro autofocus lenses a lot, but we were curious about the bokeh. We find the bokeh to be top notch as well.
Vignetting is virtually non-existent and isn't anything to worry about. We measured less than 0.1 stop at F2.8 and less than 0.05 stop at F5.6 when used on the K-5. Even on a full-frame camera, we would expect vignetting to be a non-issue but, we have not measured this.
This lens is designed as a macro lens with a flat field of focus and no distortion and we were definitely not able to detect any distortion.
We were able to provoke some purple fringing, however, but only in the extreme corners of the frame or on overexposed edges of the subject. Click on the thumbnail below to see the upper left corner.