There are also other important curves to look at.
Rodenstock always also publishes distortion, fall off and color curves as well as MTF.
As Rodenstock is ISO 9001 certified the curves published are what Rodenstock expects the customer to receive as the minimum quality level.
Thank you to everyone who has replied. The posts have been very interesting.
The MTF curves I am referring to are the ones printed in the Rodenstock literature. The Schneider ones are from their web site. Sorry I forgot to mention this.
Trevor says that all modern, computer designed lenses are first class. I agree, but still a few are even better. They are the masterpieces so to speak. Take the new Zeiss lenses for the Contax 645. Zeiss designed 7 lenses for it. All pretty much at the same time. All are first class. But one of them, the 120 Macro is a masterpiece. Why can?t the others be as good as that? Especially since they are all ?computer designed?. I don?t know.
So therefore I am trying to pick the best of the crop. And I know that not all the modern computer designed lenses are equivalent. Some ARE for sure better than others. And I want to find those! Am I being greedy? Sure.
Now coming back to the lenses, sadly Schneider only publishes MTF curves for the wide open aperture and f22 with the exception of the Super Symmar XL series. This is a pity. Why don?t they publish the MTF curves for f11 or f16? One possibility is that they are hiding them deliberately, because they don?t perform that well after all. But that is just a possibility. I know that people rave about them so they must be something to them. Moreover, I found a web page that says the Super Symmar XL 110/5.6 can resolve 80 lines per mm at f11. Now that is impressive.
For the Super Symmar XL series Schneider does publish MTF curves for an aperture other than f5.6 or f22. That aperture is f8. And sadly the curves are not impressive at all at f8 for any of them. I compared the new 80/4.5 against the Grandagon-N 75/4.5. The curves were at f8 for the Schneider and at f11 for the Rodenstock. And again the Rodenstock beat the hell out of the Schneider. But the Schneider uses aspherical elements and so should perform very well at f8. Why doesn?t it? This is a mystery.
The debate continues?
There is no mystery why some lMTF curves are at 22 while others are at 8, 16 or 11.
Manufacturers are showing the performaance curves at the diffraction limited stop. That is where you will get the best performance.
When I became wrapped up in all the technical stuff, my work suffered. I had to decide between being a photographer or a technican. It's all about knowing your equipment, it's limitations and how to use it to the fullest. I've seen beautiful work with what many here would consider to be so so or or not so good equipment. As for me, I'm glad I've passed that hurdle.
Like Jim, I constantly try to be a photographer rather than technician. But I can empathize with Mike because I have agonized over some of the same issues. The problem today, unlike a decade ago, is that with the best lenses, film and roll-backs, combined with digital scanning and printing, MF can essentially equal LF for prints up to 20x24 (in color! B&W still really benefits from larger film for reasons I don't fully understand). This of course assumes that the MF has full movements. The problem with MF is that you are always on the edge. Everything has to be right. Film flatness, not too small an aperture, fine grained film, not too much cropping and so on. With LF, there is more room for slop. Lens sharpness is not as important given enlargment factors of 5x rather than 9x, and more tolerance in film flatness and position. The tradeoff for MF "equipment angst" is less equipment bulk, more emulsion choice, lower cost and sometimes quicker shooting.
I too agree with everything Jim has said, BUT I am eternally grateful to the technicians among us who push for sharper lenses, better films, more functional cameras, etc. I salute you! Who among us wants to go back to the "good" old days of single element landscape lenses and glass plated film? Not me!
One thing to be careful about is that Rodenstock often uses f16 for the published MTF's while Schneider uses f22, and it's known that an f5.6 lens is going to give the maximum resolution on film around f11- 16. But how often does one shoot at f11-16? For me, it's more like f22-32. The bottom line is that if you need the DOF, you'll have to stop down the lens. It could be that Rodenstock's MTF's suck at f22- 32...who knows? For an LF lens, f22 is just more realistic, IMHO.
"One must stop down to the optimum aperture of each lens and not f22."
Unless you are shooting planar subjects, or are not trying to render the whole image sharp, what you loose by not having enough DOF renders the issue of lens quality moot. There is a reason why apertures of f22 or smaller are often used. As a result, I believe the difference you're reading about is not significant in practice.
James Chow, Q-Tuan Luong: Remeber, Mike wants to shoot primarily roll film. That gives him between 1.2 and 1.5 stops more depth of field than 4x5. I find on roll film that f/11-f/16 are very usable stops for depth of field when the camera has movements, unlike 4x5 where f/22-f/32 are more typically needed. In fact, that is one of the strong points of roll film, since that extra stop+ can be used for higher shutter speed, or slower film.
"One thing to be careful about is that Rodenstock often uses f16 for the publish ed MTF's while Schneider uses f22,"
Nonsense!!!!
The Apo Grandagons are diffraction limited at 11 or 16 depending on the focal le ngth. All others are diffraction limited at 22 and that is what the MTF curves are.
Note: the digital lenses are made to work at large apertures rather then small a pertures and also have MTF at apertures larger then 22. But then these lenses are for small format s or digital and don't cover 45.
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