Conflicting opinions
in 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?
"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?
3 comments
Colin Jago August 21, 2006 - 6:18Once the data is gone it is gone. You cut my quote off at the point where I went on to say that the E1 is best suited to subjects where there isn't fine detail in the first place. By preference, for much of my photography, I use a camera without an AA filter, or film.
My comments about the E1 were purely subjective. What I see is that an unsharpened raw file from an E1 looks mushy, whereas a file using the same lens on the E330 merely looks a bit soft (and again using the same lens, a file from the Leica DMR looks getting on for sharp).
I'm not sure I've ever mentioned 'recovering sharpness lost by the AA filter', but I might be wrong. What I do know is that, starting with E1 raw files, sharpening is nearly always an issue.
I think if a writer sets out to write a technical review, then all the factors need to be disclosed, down to the level of which version of which raw converter was in use. And very little can be meaningfully gleaned about a lens or a chip by reporting results from in-camera jpegs. BJP has authors who write pages and pages of stuff which all unravels when you find out that they were judging jpegs. Field reports or blog posts seem to me to require a different level of judgement. If Michael says 'in my experience this is.......' then we know what weight to put on it.
3 comments
David Mantripp August 21, 2006 - 8:11On the reason to bring you in, well basically I read all three articles (or posts or whatever) around the same time, and they just seemed to illustrate different aspects of something which continues to confuse me, which is the general idea that if an image is soft, it can be "saved", or the concept, widely held for the E-1, that it will "tolerate" a lot of sharpening.
Perceptually, a sharpened image may at a casual glance appear to have more resolution - but in fact it simply has more edge accentuation. So, for a reviewer like Vincent Luc to imply that you can recover sharpness in post processing, well it seems a little imprecise, to be kind. As for contrast - well I think that's another story, but I could be wrong.
I'm not sure why AA filtering is not done electronically. I assume it isn't, because if it were, then, presumably, you could have an option to disable it. Which would be nice.
3 comments
Colin Jago August 21, 2006 - 9:29The Leica DMR has an software moire filter which is an attempt to provide what you ask for. I didn't use it whilst I had access to the camera (that is, I always left it off). It appears as just another button on the back of the camera.
I'm assuming the M8 will have the same option as it seems likely that it will not have an AA filter.