Thu, 29 Dec 2005 07:42:51 -0800 Rob Studdert wrote: > Design, performance and build quality is exceptional on my lens however QC > wasn't great, the infinity focus point was quite badly mis-adjusted (so it > never could focus to infinity). Since this problem was remedied it's performed > flawlessly though.
I am just curious if that was an easy procedure.. What did it involve? Was it done at shop? > compare in build and performance. For a practical head to head comparison of > the SMC Pentax-A* 135mm 1:1.8 and the Voigtl.nder Macro APO-Lanthar 125mm F2.5 > SL, see: > > http://home.swiftdsl.com.au/~distudio/pentax_1351.8vsv1252.5/ Rob I believe you it is a good lens. I might be wrong, but I would argue that the tedious comparison you made might not be convincing by itself. Here is why. I am looking at Crop 1,2, and even probably Crop 3. Let me explain on the example of Crop 1. The fence on the images made with the Pentax lens is not as sharp as on the images made with Voigtlander. However on tthe photos made with the Pentax lens the dish antenna in the background seems to be sharper, what appears to be more in focus (or if you want, less out-of-focus). So, I wonder if the difference (fully or partially) in the sharpness of the fence is due to the pentax lens being focused at the point that is somewhat beyond the fence. Notice, as you close down the aperture, the fence becomes sharper (this would be consistent with the larger DOF at those apertures), but the dish is still sharper for each of the images made with Pentax. I see a similar effect in the Crop 2. Here the trees in the background play the same role as the antenna dish played in the Crop 1. The same argument is applicable to the electric pole, and the structures on the electric wires that show up from f4 on Pentax-made images, and only from f5.6 on Voigtlander-made images. The same argument is applicable to the Crop3, although it is not as obvious. Now the fence plays the role of the background object. The fence texture seems to be just a notch better resolved @ f2.5 on the Pentax image, and the grass seems to be out of focus. So, my point is that this comparison is consistent with the Pentax lens being focused at a point that is slightly farther away. On a different subject, - I am somewhat surprised by the difference in the brightness of the images at almost all appertures. At 2.5 the Pentax image is brighter, but it becomes darker at smaller apertures. I assume you were using exactly the same exposure time for both lenses. (well, was it a partially cloudy day? :-) ) Igor
