Mike Johnston said:<br /> <br /> <br /> <br /> It certainly agrees with my anecdotal evidence. I once brought home from the store five brand-new lenses--an El-Nikkor 50/2.8, a Schneider Apo-Componon-S 45mm, a Componon-S 50/2.8, a Rodagon 50/2.8, and an Apo-Rodagon-N 50/2.8--and tested them all directly against each other. The Apo-Rodagon-N was the clear winner, and the Schneider 45mm was so decentered that it was obvious it was flawed even without careful testing. It was the second sample I'd used of that lens and both samples were, in Ctein's terms, "real dogs." <br /> <br /> <br /> <br /> Mike,<br /> <br /> <br /> <br /> Can you tell me how you could tell the Schneider was decentered? Are you saying the lens elements were not aligned and not that the lens was not aligned with the rest of the enlarger? <br /> <br /> <br /> <br /> Any other tips on how to check an englarging lens?<br /> <br /> <br /> <br /> thanks<br /> <br /> <br /> <br /> dave (the lurker)<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Schneider has since replaced that lens altogether. <br /> <br /> <br /> <br /> I'm a real fan of the Apo-Rodagon-N's, although the 105mm I tested was not <br /> <br /> any particular standout. I only sold my Apo-Rodagon-N 50/2.8 when I replaced <br /> <br /> it with the Carl Zeiss S-Orthoplanar 60/4, a lens which was about eight <br /> <br /> times more expensive when it was new. <br /> <br /> <br /> <br /> <br /> <br /> > The other thing is that some lenses perform better, and are designed for <br /> <br /> > optimum performance, at certain magnifications or distance from the <br /> <br /> > baseboard. So you might want to compare the lenses with that in mind. <br /> <br /> > You might find one works best for smaller prints and the other for <br /> <br /> > larger prints. <br /> <br /> <br /> <br /> The big problem here is that most darkroom workers--certainly beginners--are <br /> <br /> not capable of employing enlarging technique good enough to see the <br /> <br /> differences. Hell, most darkroom workers stop their enlarging lenses way <br /> <br /> down, well past the optimum f-stop, so the grain is mush anyway. I'm sure <br /> <br /> you've done this, Shel, but for the benefit of others: if you take a very <br /> <br /> good grain focuser like the Omega/Peak #1 and simply look at the film grain <br /> <br /> as you stop the enlarging lens down, there's usually a very obvious optimum <br /> <br /> f-stop--starting at wide open in the center of the projected image the grain <br /> <br /> might go from indisctinct to crisp to very crisp to less crisp to mushy to <br /> <br /> very mushy as you stop down. <br /> <br /> <br /> <br /> Diffraction is a MUCH bigger problem in the enlarging system than in camera <br /> <br /> lenses. The only reason to buy "apo" enlarging lenses is that they are <br /> <br /> diffraction-limited half a stop or a full stop wider open. Any lens that <br /> <br /> allows you to print wider open will be better--Ctein and Arthur Kramer, the <br /> <br /> lens guru from _Modern Photography_ who started all this lens-testing <br /> <br /> business way back when, used to have a running argument about which was <br /> <br /> better--Arthur's Apo-El-Nikkor 105mm, which was diffraction limited wide <br /> <br /> open at f/5.6, or Ctein's garden-variety but tested and hand-picked <br /> <br /> Rodagons, which were diffraction-llimited at f/4.5. Arthur actually won that <br /> <br /> argument when Ctein finally got to test an Apo-El . But Ctein had a good <br /> <br /> point. <br /> <br /> <br /> <br /> My S-Orthoplanar is diffraction limited wide open. It beats the <br /> <br /> Apo-Rodagon-N by half a stop. Awesome lens. <br /> <br /> <br /> <br /> - -- Mike <br /> <br /> <br /> <br /> "Ain't photography grand. The more you know the less you know." (Shel <br /> <br /> Belinkoff) <br /> <br /> <br /> <br /> * * * <br /> <br /> Find out about Mike Johnston's unique photography newsletter, "The 37th <br /> <br /> Frame," at http://www.37thframe.com<br /> <br /> <br /> <br />
------------------------------------------------------------------------ <br /> <br /> <br /> ------------------------------------------------------------------------ - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
