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Photography , Monday, August 21, 2006
In the last couple of days, two widely conflicting opinions have been published on the Leica zoom lens which ships with the new Panasonic Lumix L1 camera. Vincent Luc, writing in Réponses Photo, is disappointed with it. Not that it is bad, but he finds that the sharpness and contrast are simply not up to the expectations associated with Leica. He does, however, add that there might be some scope for improving matters in post-processing. Now, Vincent Luc is no idiot, and the review is well considered and comprehensive, nothing like the recyled PR and datasheets that most web sites pass off as "reviews". One website which certainly does
not fit that in category, however, is The Luminous Landscape. Michael Reichmann, in
his L1 review, has a radically different view:
"Having taken many hundreds of frames with this lens during my week in Iceland I can tell you that this is one first-rate optic. No formal tests are needed to let me know that this lens is sharp, contrasty, and quite free of any serious aberrations at least those visible without conducting a formal test suite".
Going back to the post processing issue, it is interesting to pick up on a
recent post by Colin Jago, discussion in this case the sharpness in general of Olympus E-1 images (let's just imagine that the E-1 has the fully compatible Leica zoom attached). He observes:
"(...) one of the things that you always have to bear in mind is that you only have 5 megapixels to play with. Further, these are quite soft megapixels (the anti-aliasing filter). Whilst I think that properly sharpened native resolution prints from the E1 can be fantastic, (...)".
So what is everybody actually talking about here ? First, whilst I suspect that the Vincent Luc's results are based on JPGs, I'm sure Michael's and Colin's are based on RAW. The almost diametrically opposed opinions of the lens sharpness and contrast are striking. But... is Michael talking about the results as seen (and maybe optimised) in Adobe Lightroom?
Both Colin and Vincent Luc talk about recovering sharpness lost by the anti-aliasing filter, and this where I really start to lose the plot. An AA filter is a low pass filter, usually with an abrut cutoff. It is designed to prevent the sensor from recording high frequencies which it cannot unambiguously resolve. I don't want to go into a long discussion on filtering here, but in this type of setup essentially any data blocked by the filter is gone and no amount of post-processing can bring it back. Frequencies near the cutoff frequency will be attenuated. In photography terms, this translates as an irrecoverable loss of fine detail, or more accurately, a limit on the level of fine detail that can be captured. This is obviously extremely simplistic, and people could - and do - drone on for hours about it.
Sharpening in software can give a percerption of a more detailed image, by subtle enhancement of the actual detail. But doesn't make the lens sharper or more contrasty.
The approach of evaluating the camera-lens pair using DxO's system seems to be the only consistent way to review digital systems. But when the reviewer is looking at photographic output, as the three I quote here are, then the software plays an equally important part, and should be explicitly declared.
>Perhaps we should start to talk about lenses in a different way, saying for example that on camera X, processing with software Y, lens Z does not limit resolution or inhibit contrast. Then maybe it becomes easier to understand how two highly competent reviewers can draw such different conclusions.
So, is the Leica lens a dog or a gem?