Collin wrote:
> On the top photo, taken with the 77, the light reflections in the leaves have > a definite doughnut character. > > Same with the reflections off the tail light of the white (does that say > "Park") minivan. > > Doesn't look good for the 77. Am I wrong? Yes, doughnuts happens with all lens at certain conditions due to the laws of optics. If you scan through the Pentax photo annual books you'll see virtually all lenses made by Pentax creates this effect under certain circumstances (this includes lens as diverse as the M 200/4, FA 80-200/2.8, M 40/2.8, 43 Limited, 105/2,4 (for the 67), A 85/1,4 etc). You can scan Leica books, Nikon books, National Geographic books et. and see the same effect. This effect happens when highlights is at a certain level of defocusing. With further defocusing they take aperture shapes. They go from circular to doughnut shaped to aperture shaped to completely smeared out with increased defocusing. Hence, lenses with the most circular aperture holes (many aperture blades) will keep the round shape the longest. To avoid it is basically to avoid highlights at a certain distance from the focusing plane. Some lenses are more prone to this than other simply due to the way lenses are most often used and the DOF displayed with such usages. P�l
