This lens is noticably lighter than their 300mm. The change from the old four element version 200 is the addition of one more element and the close focusing is improved. The old version(Takumar) would not focus close enough to do a head shot, while the new version will. The optical design is quite different from the Takumar. The Pentax has four elements in the front group with only one positive element in the rear. It's a very strange telephoto design. There seems to be much controversy about the performance of this lens. With light weight tripods it is prone to shutter shake. Some have claimed that this lens is junk but I must ask; what tripod are you using? With ten pound tripods, this lens is sharp enough for commercial work. It will resolve at least 30 lines per mm at f/32. Its best stops for sharpness are 22, 16, 11 and 8. Do not use this lens with the center post of your tripod extended. Shoot as close to the ground as possible. This is a portrait lens and can be hand held easily with the right film. It is a fairly good lens for macro work when used with tubes. Macro sharpness as with any telephoto design is not going to be as good as lenses designed for close ups. Now, if it just had more DOF. Steve

-- Steve Rasmussen (srasmuss@flash.net), January 05, 1999

Answers

I have never seen what you art describing in my macro work with this lens. It is however possible, considering what you are shooting. The cause is longitudinal chromatic aberration and specifically, spherochromatism. To eleiminate the fringing, I suggest using a slightly faster film and stopping down more. Fringing is always worse wide open and at f/5.6 than at 8, 11, 16 etc. Using an achromat with this lens would probably make matters worse.SR

-- Steve Rasmussen (srasmuss@flash.net), February 10, 2000.

Leendert, even though the 200mm is tele in focal length, it is not actually a telephoto design. It is called an Ernostar. Yes it is very asymmetrical and when stopped down does well in close focus situations. At wider apertures, close up, however, it can't compete with the symmetrical and semi-symmetrical designs. I feel that Pentax should have made its portrait lens a 180mm f/2.8 low dispersion Double Gauss. BTW, the Ernostar design is fairly new for Pentax.Both the 165 f/4 LS and the 200 are this type. Leica uses this design extensively. Your problem with asymmetrical out of focus images could be caused by a slight amount of lateral chromatic. Not sure. SR

-- Steve Rasmussen (srasmuss@flash.net), February 13, 2000.

I am not so enthousiastic about the the close-up performance of the 200mm/F4 Pentax,espescially with portraits. For instance, in a high-contrast situation like back-lit blond hair in a head and schoulder or three-quarter portrait I see small red lines on one side of the hairs. Bright spots that are outside the plain of focus frequently turn out green and red instead of white-I find that less pleasing. Probably all this is caused by residual chromatic aberration. At greater distances I found the lens very sharp, even at F5.6. (but that was not where I bought the lens for). Could a small (0,5-0,25D) achromatic close-up lens improve the close-up performance?

-- Leendert van de Klippe (leenvdklippe@hetnet.nl), February 09, 2000.

Thanks Steve, you are right, the "red line effect" that I saw was at f5.6 and minor, only visible in the highlights. I want to add another observation concerning the way the lens deals with out of focus part of the picture, especially the area at the border of sharpness/unsharpness. In this area the 200 seems to render the out-of-focus part different than the 165/2.8. What I mean by this is for instance: A hair behind the plain of focus is "asymmetric unsharp". What I mean by this is that not the whole hair is unsharp, but only the side that is facing the edge of the frame, while the side of the hair facing the center of the frame has a sharp edge. Other lenses don't seem to have this, my 100/4 renders beautiful "symmetric" unsharpness in close-up. The 165 also seems better in this respect (I rented one a few years ago). Maybe because of this reason Pentax calls the 165's "portait lenses" and the 200 "tele" in their brochure, and are the 165"s optimally corrected for "portret distance" and the 200 corrected for greater distances. The 200 being a very asymmetrical lens design is probably not so good for distances it is not optimally corrected for, maybe causing extra chromatic aberration and/or curvature of field. I ask this question since you also seem to be interested in optics, judging from your excellent forum, and hope that you don't find it a too boring topic! Greetings, Leendert. P.S., compared with a 1960's Apo-Ronar 240mm/f9 fixed to my Px, the Pentax 200 is less sharp in close-up (no surprise), but image contrast is much higher with the Px, I have to print 1-2 grades higher with the Rodenstock (the benefit of multcoating most likely, since the German has a single coating, and some dust collected over 30+ years as a reprolens). At infinity there's not much difference in sharpness, Px having again much higher contrast/color saturation. The Apo-R has in my opinion a nicer kind of unsharpness, close-up and far away, but was akward to use, so I sold it (manual diaphagm only).

-- Leendert van de Klippe (leenvdklippe@hetnet.nl), February 13, 2000.