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 p.11 #1 · Digital-Picture review ZE 100 MP lens | |
wickerprints wrote:
And then you see from the test charts that it has more axial color than the EF 100L from f/2 - f/2.8. What does that say about how people choose to see what they want to see? If you compare the Photozone test charts, according to them, the 100 MP has as much resolving power in the center at f/2 as the 100L at f/2.8. That clearly contradicts the actual test charts from TDP showing magenta fringing in the former at f/2.
Speaking of choosing, I think you choose not to see lateral chromatic aberration in the TDP comparison. 
Contrary to what you claim above, one cannot see from the TDP test chart that the Zeiss has more axial colour, because one can't determine from the test chart that the tester focused accurately, and mis-focusing would precisely produce the magenta tint observed. In fact, all signs (the results, the Photozone results, Zeiss' MTF charts, real-world photos, etc.) point to his having slightly missed focus for the Zeiss. (And several other lenses he's tested. I've examined a bunch of them. In addition to sometimes straightforwardly missing the focus, he more often fails to choose the focus point that best accommodates curvature of field across the test chart. A careful photographer will obviously choose that point in real-world shooting, when time permits.)
Modern, highly corrected, fast lenses — such as the Zeiss in question — produce very saturated false colour when slightly mis-focused, unlike older lenses with dominant monochromatic aberrations. This is its own flaw, but shouldn't be confused with false colour in the plane of focus.
I have my issues with Lloyd Chambers' tests and interpretations, but he does manage to get things in certain focus before coming to any grand conclusions. (Moaning about the difficulty of achieving truly accurate focus is one of his recurring themes, of course.) And I suspect the reason he finds so many lenses to be duds is that he tests them more rigorously than most people. I also suspect a lens with fifteen elements, image stabilisation, and a plastic barrel will more often have centring issues than a Zeiss. Call it speculation if you wish! Here's what the 18 mm f/3.5 ZF looks like inside (photo taken at last year's Salon de la Photo in Paris):
http://img207.imageshack.us/img207/585/zeiss18mmbetter.jpg
This approximate style of construction is used for Leica lenses, modern cine lenses, and high-end Canon lenses like the super-telephoto models (I'm not sure about the new lightweight versions). Lenses like the Canon 100 mm f/2.8L macro, by contrast, are put together with generous amounts of plastic and glue. This makes them light, affordable, and largely good enough; but it does mean they're more liable to centring problems, both when new and after use (knocks, bumps, falls).
Edited on May 27, 2011 at 02:26 PM · View previous versions
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