Your analogy is not a good one, because the tests I cited are not from the lensmaker.
It's from a photographer who was interested in the following question:
"What is the resolving power of medium format lenses?"
And he set about testing a LOT of them. He picked a methodology that was imperfect, but uniform. He tested them the same way.
Furthermore, the tests were not MTF tests! They were line pair tests. The target doesn't matter as long as it's the same target, the same shooting distance, and the same lighting -- and the tester knows how to count. Even if he did the test wrong, the results remain meaningful as a relative comparison of resolution among the lenses he tested, as long as he used the same methodology for all lenses.
You can dismiss the tests if you want. But unless you have the wherewithal to test every lens yourself, by the criteria that matter to you, you're left with no other basis to compare them objectively.
The few lens designers I've met also shoot with their lenses. Several are enthusiastic photographers. They freely admit that no matter how well you meet objective criteria, you don't necessarily get a lens that gives good pictures -- and vice versa, as witness the current 50/1.5 Sonnar.But they sure as hell don't dismiss either objective or subjective criteria.
People often quote the results but ignore the comments. I think the main point of the Perez tests isn't that one or another is better but how small any difference is. This is even more of an issue when looking at his LF tests at working apertures. The worst coke bottle at the sort of F/stops often used for 8x10 isn't a great deal worse then the latest kilo buck lens.
Obviously there is a big difference in culture between small format and medium and large. I think we have to bear in mind that different people in this thread are coming from very different places.
As they probably should, many 35mm shooters do tend to know a thing or two about MTF and CA and all that. And along with that comes some amount of equipment snobbery. Some of it is justifiable, some is not. Look, people are now shooting colour and over a broader ISO range than in HCBs day I don't mind a stimulating debate about Leica vs. CZ.... in the case of 35mm lenses. One also sees some of that attitude in MF but far more rarely in LF. Yes I am generalizing, I know that everyone can name exceptions. But seriously, most of this chatter is entirely cultural.
As for me, when I consider new 35mm lenses (e.g. the new ZF lenses) I do definitely consult the charts and ask myself what I might be getting. I pay even closer attention if I expect to put the lens on an APS digital. But for LF, well, I have two ancient convertible lenses that are poorly ranked but which I adore. They really deliver. During those rare moments that I covet a brand new APO Schneidagon XXX for $4000 I simply remind myself about all those LF photographers who did far more with far less.
Back to the RB and RZ lenses.... About a year ago I took a hammer to an old RB 127 f/3.8, I wanted to excise the leaf shutter mechanism and had given up trying to dismantle the thing in a controlled way. Wham! with a hammer. Nothing. Bam! right on the rear element! Little chip on the side. What the f...?! Threw the thing against my patio. Wanna see the dent in my patio? I still keep that lens as a paperweight, I did succeed in cracking the rear element but never got it to actually fall out, and the barrel is fine.
All I can say is, the RB lenses would make marvelous artillery projectiles- who needs depleted uranium when old RB lenses are so inexpensive.
Last edited by keithwms; 08-30-2007 at 05:35 PM. Click to view previous post history.
Originally Posted by Nick Zentena
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Good point. You must take into consideration both objective and subjective criteria.
Originally Posted by Roger Hicks
A lens that tests very high in lppm is not necessarily a great lens for making real pictures, though IMHO it will be more often than not.
On the other hand, a lens that is a real dog in resolving power in lppm will almost never be a great lens for a wide variety of subject conditions, unless the deck is stacked toward an image that favor some type of lens aberration.
On the other hand, many people love the images they get from Diana and Holga cameras. Go figure.
Last edited by sanking; 08-30-2007 at 11:40 PM. Click to view previous post history.