Archived posting to the Leica Users Group, 2004/01/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks for the very informative reply Seth. The reason I asked about chromatic abberations is because I have several DR's S/Ns ranging from 1,7xx,xxx to 2,2xx,xxx and also examples of the later 50mm Summicrons; not one of the DR's gives me the "snap" of the later lenses, yet your data seems to indicate comparable MTFs. I am trying to figure out why. FWIW, the lenses range from truly Exc to " boxed, as new" and show no signs of mechanical abuse or misalignment. One further question, if I may. What did Optikos charge you for the tests and what was the lead time ? By the way, many years ago an LHSA member based in Las Vegas, whose name I no longer remember, told me that he had attended a Photokina where an optical house, Novoflex IIRC, had an MTF tester set up and were testing lenses for the public. He had his filters tested and his Tiffens did very well. This was in the late '80's early '90's. I bought a 400/5.6 Telyt from him. Wonder if he is on thsi list? Regards, Akhil - ----- Original Message ----- From: "Seth Rosner" <sethrosner@direcway.com> To: <leica-users@mejac.palo-alto.ca.us> Sent: Friday, January 09, 2004 10:31 Subject: Re: [Leica] DR Summicron MTF (was: For your information) > To Akhil and Lee: > > Yes, Lee, when I find the time there will be a VIEWFINDER piece about the > tests; also of the pre-ASPH and the first 8-glass 35/2 Summicron and the > 35/2,8 Summaron. > > Since this is the Leica USERS Group, let me agree up front with Ted, B.D. > and a myriad other LUG friends who have consistently said: "use your > equipment to take photographs. If your lens produces what you want, you > should be happy." > > As many of you know, that thought process is exactly what led me, a good > number of years ago, back to the DR/Rigid Summicron as my main user 50, > after having used the successor 50/2 Summicron (11817) and, briefly, the > current 50/2 (11819 et seq). Most of my photography is at f/4, 5,6 and 8. > When I need speed, I use the 50/1,4 Summilux. And at those intermediate > apertures, in my opinion the DR/Rigid produces images that most please me. > Not only in b+w but especially on Kodachrome, my most used color film. > > Precisely because I don't typically need the speed, like our dear friend > Steve Lehuray, for me the old 35/2,8 Summaron produces marvelous images > approximating the image-making of the DR. That actually was my primary > motivation in setting up these tests: comparing the Summaron with the > 8-element and the pre-ASPH 35/2 Summicrons. Then I said to myself, having > driven all the way to Cambridge, while there, if they will let me, why not > test the DR/Rigid 50 with Alpa's legendary 50/1,9 Macro-Switar. So we did. > > Akhil asked: > > > > What light source did you use and did you check for chromatic abberartions > and light fall off? > > How the EROS test equipment works is far beyond this non-techie. But I do > know that we tested with a visible white light source. We did not test with > color filters so no test for chromatic aberrations. The machine uses a light > slit aimed at the lens. It was collimated only for infinity. > > This is a fairly lengthy process, setting up each lens, focusing, then > testing (inputting to the computer) at each aperture from initial to f/8 (we > didn't stop down further since on these lenses diffraction begins seriously > to affect optical performance after f/8) and then testing on-axis, at 12mm > off-axis (the near edge) and at 18mm off-axis (the far edge). And remember, > we were testing five lenses. I couldn't ask Roy Youman, the fellow at > Optikos who did the testing, to spend any more time than the several hours > we already did. > > > Were you able to test a current Summicron M or R at the same time? > > No. > > Seth LaK 9 > > -- > To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html > > - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html