theSuede wrote:
The reasons why Leica don\'t incorporate AA filters into their designs are quite simple:
1) they cannot afford it
2) since they\'re already using the cheapest, cheesiest materials available for the filter package, an AA filter would add to much thickness, and make the edge colour vignette even worse.
The reasons why MF manufacturers don\'t inlude AA filters:
1) they cannot afford it
Um..No, I\'m not buying that. For several reasons. First if you look at papers published on the subject you\'ll see that it\'s a very old discussion. Here\'s for instance a paper from 1974(!). You can look in modern literature as well, like The Manual of Photography 10th edition (2011) and you\'ll get back to the same conclusions:
There\'s always a tradeoff between aliasing and MTF and when you put an optical low pass filter in the way, you have to deal with its MTF as well. Its optical characteristics will inevitably negatively impact what you get out of the lens - and not just at the frequencies you want.
Second, the economic argument doesn\'t cut it. AA filters are not something particularly expensive - even the cheapest P&S cameras have them.Furthermore thinking that digital backs with $50,000 price tags that have been designed to maximize optical performance would cut costs by skipping such a trivial component isn\'t plausible. Leica\'s ways when it comes to cost cutting may be mysterious, but the same cannot be said for for instance the Leaf Aptus 80. Of course, that wasn\'t the reason for Leica either - they declared their design goals when they released the M8. In fact with the M8 they went further and did not include an IR filter claiming that one would affect image quality and that it was better to have one mounted on the lens.
Not a very practical decision and most people hated it, but they were right. The M8\'s per pixel sharpness is slightly (really really slightly...but still) higher than the one of the M9. You are right that the M9\'s IR filter is crap as IR filters go, but that\'s again by design. They chose the thinnest (most flimsy one as you expressed it) one and optically least effective they could get away with. Subsequently the IR issue is solved for the most part, but not entirely - you can still get a purple cast on some black synthetics. The impact on image quality is though as minimal as it can be.
Their reason for not having an AA filter is the same - they prefer to use the full sensor resolution rather than solving the problem by increasing pixel density. My 18 megapixel M9 easily outresolves my 21 megapixel 5DII and I can make larger high quality prints with it. You have to go up to the 24 megapixel D3X to match it. Some tests show that it even outresolves the D3X, but I personally don\'t put too much stock in them - from most tests I\'ve seen they seem to be matched in that department.
2) they expect their users to be aware of the effect and do what they can when shooting to avoid it.
That I do buy. Aliasing is problematic in some cases and you have either avoid it, fix it in post or simply ignore it. If there was somebody demanding AA filters it would potentially be medium format digital back users as MFDBs are very often used in fashion photography and you how \"lovely\" the combination of textiles + no AA filter can be. And yet they don\'t. The reason is simple MFDBs are in a megapixel race, but not one equivalent of the P&S cameras a couple of years ago. Here the quality of the pixels matter as the resolution tells you how large you can print. And that\'s why most MFDB users would rather eat their camera than to let the integrity of their dear expensively purchased pixels to be violated by a brute optical low pass filter.
Colour aliasing issues can never be \"fixed\" though, and the destructive power that effect wields is present at any magnification.
Actually fixing color aliasing is trivial. Switch to lab mode and lowpass filter the a & b channels.
Example - full image:
100% crops: left side, natural, right side a&b channels with a bit of gaussian blur added to them.
As you can see all the color artifacts are gone. And the drop in color detail is not something you can readily pick up. Our eyes are far more sensitive to b/w detail than to details in colors.
theSuede wrote:
The reasons why Leica don\'t incorporate AA filters into their designs are quite simple:
1) they cannot afford it
2) since they\'re already using the cheapest, cheesiest materials available for the filter package, an AA filter would add to much thickness, and make the edge colour vignette even worse.
The reasons why MF manufacturers don\'t inlude AA filters:
1) they cannot afford it
Um..No, I\'m not buying that. For several reasons. First if you look at papers published on the subject you\'ll see that it\'s a very old discussion. Here\'s for instance a paper from 1974(!). You can look in modern literature as well, like The Manual of Photography 10th edition (2011) and you\'ll get back to the same conclusions:
There\'s always a tradeoff between aliasing and MTF and when you put an optical low pass filter in the way, you have to deal with its MTF as well. Its optical characteristics will inevitably negatively impact what you get out of the lens - and not just at the frequencies you want.
Second, the economic argument doesn\'t cut it. AA filters are not something particularly expensive - even the cheapest P&S cameras have them.Furthermore thinking that digital backs with $50,000 price tags that have been designed to maximize optical performance would cut costs by skipping such a trivial component isn\'t plausible. Leica\'s ways when it comes to cost cutting may be mysterious, but the same cannot be said for for instance the Leaf Aptus 80. Of course, that wasn\'t the reason for Leica either - they declared their design goals when they released the M8. In fact with the M8 they went further and did not include an IR filter claiming that one would affect image quality and that it was better to have one mounted on the lens.
Not a very practical decision and most people hated it, but they were right. The M8\'s per pixel sharpness is slightly (really really slightly...but still) higher than the one of the M9. You are right that the M9\'s IR filter is crap as IR filters go, but that\'s again by design. They chose the thinnest (most flimsy one as you expressed it) one and optically least effective they could get away with. Subsequently the IR issue is solved for the most part, but not entirely - you can still get a purple cast on some black synthetics. The impact on image quality is though as minimal as it can be.
Their reason for not having an AA filter is the same - they prefer to use the full sensor resolution rather than solving the problem by increasing pixel density. My 18 megapixel M9 easily outresolves my 21 megapixel 5DII and I can make larger high quality prints with it. You have to go up to the 24 megapixel D3X to match it. Some tests show that it even outresolves the D3X, but I personally don\'t put too much stock in them - from most tests I\'ve seen they seem to be matched in that department.
2) they expect their users to be aware of the effect and do what they can when shooting to avoid it.
That I do buy. Aliasing is problematic in some cases and you have either avoid it, fix it in post or simply ignore it. If there was somebody demanding AA filters it would potentially be medium format digital back users as MFDBs are very often used in fashion photography and you how \"lovely\" the combination of textiles + no AA filter can be. And yet they don\'t. The reason is simple MFDBs are in a megapixel race, but not one equivalent of the P&S cameras a couple of years ago. Here the quality of the pixels matter as the resolution tells you how large you can print. And that\'s why most MFDB users would rather eat their camera than to let the integrity of their dear expensively purchased pixels to be violated by a brute optical low pass filter.
Aug 17, 2011 at 05:21 PM
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