Questionable Lens Redesign Philosophy

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I used to think that Pentax would only redesign a lens when they felt they could improve it. This would be in keeping with traditional Japanese quality practices. The 200 Takumar VS the Pentax version really makes me wonder why they went to the Ernostar design on the newer one.(Maybe they felt that if Leica used it, then it must be good). The Takumar 200 seemed like a great lens. Discontinuing the 150mm and going to a different design 165mm(Double Gauss)seemed odd. It would make more sense to optimise the 150mm design and make it a 165 rather than go with a completely different design on the 165. The 400 Takumar is a really nice lens and retains the helical focusing of the 300mm and has the much needed tripod mount that the old 300 didn't get. Color correction doesn't seem to be a problem with the 400 Takumar even though it uses conventional glass. The diaphragm is the great 12 blade type of the 600 but without the 600's rack and pinon focusing(YUK!). Going to an ED and expensive version on the 400 could be more about marketing than performance. I guess I have two points to make: 1. Why don't they optimise their existing designs on their redesigns? 2. Why do they change the design when the previous version seemed outstanding? SR

-- Steve Rasmussen (srasmuss@flash.net), June 21, 2000

Answers

The 165mm f/2.8 has had many comments from users saying both that it is very sharp and also just so-so. The 105 has had the same disparate views but is safe to say that wide open it is not sharp off axis. There have been comments that the 200mm Takumar was some users' sharpest lens. Others said that it was nothing special. There has never been controversy about the first 55mm f/4 being mediocre. There is agreement that both 75mm lenses are sharp as well as the 45, latest 55mm, 135 macro, 150 Super-Takumar/Takumar, 400ED and 800ED. I have never been thrilled with my 200 Pentax's performance although it is not soft. I prefer my 150 Super-Takumar over it and feel the 150 is way sharper wide open. All this reopens the issue of quality variations from Pentax. I cannot enjoy the benefits of a redesign when lenses vary enough to negate those benefits.

-- Steve Rasmussen (srasmuss@flash.net), June 22, 2000.

Stefan, there have been only two versions of the 200mm but comments vary considerably as to the sharpness of the Takumar. SR

-- Steve Rasmussen (srasmuss@flash.net), June 24, 2000.

Steve,do you mean the 200mm Takumar is at least as good as the current 200mm Pentax? This would surprise me,since I've read quite a few comments that suggested to "stay away from the old 200mm". Or have there been more than two versions of the 200?

-- Stefan Geysen (stefan_geysen@hotmail.com), June 22, 2000.

I can't comment on the 200mm and 300mm lenses but I am quite dissapointed with the performance of the 165mm F2.8 lens. Even at high shutterspeeds on a Gitzo 1340 from F5.6-F16 the resolution seems acceptable at best, it never really excells. I use a 7x anastigmatic Peak loupe to check sharpness and I think the only thing this lens has going for it is that an elargment of only 4-5x is required for a 8 x 10 inch print. I don't understand why they would change the 150mm lens which has many good reports and replace it with the 165mm which is average at best. In comparison the 105mm F2.4 lens has quite good resolution from F8-F16 I haven't tested the other apertures. I also have the 1st version of the 55mm F4, at F5.6 it is pathetic, but from F11-22 the results are great. I can understand why it was updated later on. In short Pentax should change lens design if their is a benifit for the user and I don't see this with the change from the 150 to 165mm lens. Most people use medium format for the image quality, thats why I bought into this system and its dissapointing to see that there are so many questions as to the performance of some lenses and it seems that not every complaint is unfounded.

-- Chris Georgiopoulos (chrisgeorge@bigpond.com), June 22, 2000.

I have the newest 55, 105 and 200. My thoughts both testing and shooting B&W with these lenses is as follows (I only test for center resolution, primary to sort out the dogs and determine the optium F-stops, I am NOT a lens testing NUT):

The 55 f4 is an unbelievable sharp lens from wide open to f-22 period! I love this lens and ranks third in my personal line of lenses if I only could have three. The second is my 80-200 f2.8 AF nikkor and number one is my 55mm micro nikkor.

My 105 f2.4 cuts 66lp/mm wide open, goes to the mid 90's at f5.6 and goes to hell (31 and 30 lp/mm respectively) at f-16 and 22. I try not to shoot below f-11 with this lens. This also the least used of the three 67 lenses.

The 200 f4 test wells at all but f22(60 lp/mm-which isn't that bad). However, I have made a lot of negatives with this lens that were not up to my sharpness expectations in a 16x20 or larger print. I think is has more to do with the longer focal length and the dreaded shutter shake, then the lens performance. I've been using a 3047 bogen with a 3046 head and the "press on the penta prism technique"(MLU always) at any thing below 1/250 lately with this lens. I think I see some improvement, but have not shoot enough yet to feel that I have the problem licked.

My $0.02 worth.

-- Gene Crumpler (nikonguy@worldnet.att.net), June 22, 2000.



I can't understand why there is such variation in quality for some P67 lenses. Pentax surely are able to produce consitent quality from batch to batch. They will only lose potential customers if their quality varies from batch to batch. Or is the problem how we evaluate results. I can see with my 7x lupe a distinct difference in the resolving power of my 165mm lens and my 105mm lens.

-- Chris Georgiopoulos (chrisgeorge@bigpond.com), June 28, 2000.

Chris,

What about using strobe to eliminate all shake problems? I shoot my 6x7 nearly 100% with strobes, and have been entirely satisfied with my results. I routinely shoot at f/22 with the 90LS, 135, and 200 lenses with Norman P2000D power supplies. If you suspect shutter problems as the cause of your sharpness issues, use strobes to avoid it during the test.

Shoot news print or something with discernable fine detail. I shoot news print at an angle, with the point of focus on a black line I draw vertically down the center of the page. I use the stock page from the newspaper. Shooting at an angle will show you a focusing problem. If the band of vertical focus differs from the black line, your film plane and viewing screen do not agree. Time for a trip to the service man.

-- Bruce Gavin (doc@compudox.com), June 28, 2000.


Bruce,

I did have a problem at first with camera shake but not since I started using a Gitzo 1340 even at the critical 1/15 and 1/8 sec speeds I now get good results. All my comments are from shooting on the Gitzo. Yes, strobes will help sharpenss but this is not practical for landscape work which is what I mainly shoot. I have never tested any lens on test charts, but only in the field. My question is everyone seems to have a different perseption to sharpness and this a possible problem. Also I must say that even lenses with so-so resolution like my 165mm F2.8 lens when shot at F8-F11 give acceptible results with proper technique. But for a prime lens for any 6x7 system I would expect better performance. I have not read one bad comment about the Pentax 645 lenses yet, but there is a lack of consesus as to the quality of the 6x7 lenses.

-- Chris Georgiopoulos (chrisgeorge@bigpond.com), July 15, 2000.


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