Previous versions of brainiac's message #7846965 « Canon EOS 7D Master thread »
brainiac Offline [X]
Re: Canon EOS 7D Master thread
theSuede wrote:
Since it\'s hard to make a filter material very dense optically without at the same time making it very uneven in physical quality (which is a no-no in semiconductor manufacturing), the (lack of) thickness of the CFA plate indicates at least a doubling of transmittivity. If the used materials are the same, then scale dictates that the filter plate thickness should be at least two times thicker than it is depicted. This would make the cell filterplate at least twice the depicted height, and hence VERY sensitive to angle errors. In short - the sensor would be totally useless with anything below 100mm (unless perfectly retrofocal) or F/4.
And rest assured, if a new, super-filter-material had surfaced, larger sensors would have received it\'s blessings at the same time as smaller sensors.
High filter transmittivity is good for noise characteristics, and VERY bad for colour accuracy. To use a very recent example, the 5D (original) can accurately discriminate between twice as many individual hues per frame as the 5D2, even though the 5D2 has a higher signal to noise ratio per area unit (at the same exposure) AND higher resolution. All due to filter dilution, to get lower noise. The greens of the 5D2 are twice as diluted as in the 5D, and the other two primaries got their share with the ugly-stick too. This leads to quite a few problems with metamerism, and an uneven hue transition curve in between the primaries (most commonly known as \"Canon skin tones\"). The colour profiles used with the 5D2 in raw converters needs to be quite a lot sharper and more radical in their corrections than the ones used for the 5D. And higher resolution corrections invariably leads to very much worse \"worst case\" errors when the profile is used on WB-temperature outside the (in this case) very narrow \"best use\" window. The latest X-rite \"Passport\" only corrects for six points around the HSL hue-circle, and this is not nearly enough to ply the colours of the 5D2 back into shape. 36 would be more appropriate.
Example in case:
I can make a reasonably accurate profile for a 5D in very difficult fluorescent lighting quite easily. This is almost impossible with the 5D2. The error margins will be higher than the correction accuracy.
Now lower the colour-accuracy of the 5D2 by a factor of three, and you have a working 2um cell.
I think this is very interesting, although I\'m not sure how much reality it reflects. I do indeed notice a certain fragility in 5D2 colour, and often a sense that the colour palette is somewhat limited, particularly in the deep shadows where a green/magenta duality seems to take over.
However, I do get great results on skin from my 5D2\'s by applying my own profiles, which are suited to different kinds of picture, and I don\'t find that the 5D competes generally in overall image quality, including the colour characteristics.
My 1Ds3 colours felt a little more robust in processing, which illustrates that this is not a problem inherent to high density sensors, but might instead be only a question of the colour filters. My 1Ds3 was great at iso 12800.
Limited colour palettes were what gave films like Kodachrome their beloved warmth. If you walk around the Louvre you won\'t find a priceless painting which contains as wide a gamut as the 5D2 can capture. The 5D2\'s colour characteristics must be wielded judiciously, but they can be. I certainly hope that future cameras have a more accurate and uniform response to different colours of light source, but for the moment we must make the best of it.
Dec 03, 2009 at 09:42 AM
brainiac Offline [X]
Re: Canon EOS 7D Master thread
theSuede wrote:
Since it\'s hard to make a filter material very dense optically without at the same time making it very uneven in physical quality (which is a no-no in semiconductor manufacturing), the (lack of) thickness of the CFA plate indicates at least a doubling of transmittivity. If the used materials are the same, then scale dictates that the filter plate thickness should be at least two times thicker than it is depicted. This would make the cell filterplate at least twice the depicted height, and hence VERY sensitive to angle errors. In short - the sensor would be totally useless with anything below 100mm (unless perfectly retrofocal) or F/4.
And rest assured, if a new, super-filter-material had surfaced, larger sensors would have received it\'s blessings at the same time as smaller sensors.
High filter transmittivity is good for noise characteristics, and VERY bad for colour accuracy. To use a very recent example, the 5D (original) can accurately discriminate between twice as many individual hues per frame as the 5D2, even though the 5D2 has a higher signal to noise ratio per area unit (at the same exposure) AND higher resolution. All due to filter dilution, to get lower noise. The greens of the 5D2 are twice as diluted as in the 5D, and the other two primaries got their share with the ugly-stick too. This leads to quite a few problems with metamerism, and an uneven hue transition curve in between the primaries (most commonly known as \"Canon skin tones\"). The colour profiles used with the 5D2 in raw converters needs to be quite a lot sharper and more radical in their corrections than the ones used for the 5D. And higher resolution corrections invariably leads to very much worse \"worst case\" errors when the profile is used on WB-temperature outside the (in this case) very narrow \"best use\" window. The latest X-rite \"Passport\" only corrects for six points around the HSL hue-circle, and this is not nearly enough to ply the colours of the 5D2 back into shape. 36 would be more appropriate.
Example in case:
I can make a reasonably accurate profile for a 5D in very difficult fluorescent lighting quite easily. This is almost impossible with the 5D2. The error margins will be higher than the correction accuracy.
Now lower the colour-accuracy of the 5D2 by a factor of three, and you have a working 2um cell.
I think this is very interesting, although I\'m not sure how much reality it reflects. I do indeed notice a certain fragility in 5D2 colour, and often a sense that the colour palette is somewhat limited, particularly in the deep shadows where a green/magenta duality seems to take over.
However, I do get great results on skin from my 5D2\'s by applying my own profiles, which are suited to different kinds of picture, and I don\'t find that the 5D competes generally in overall image quality, including the colour characteristics.
Limited colour palettes were what gave films like Kodachrome their beloved warmth. If you walk around the Louvre you won\'t find a priceless painting which contains as wide a gamut as the 5D2 can capture. The 5D2\'s colour characteristics must be wielded judiciously, but they can be. I certainly hope that future cameras have a more accurate and uniform response to different colours of light source, but for the moment we must make the best of it.
Dec 03, 2009 at 09:30 AM
Previous versions of brainiac's message #7846965 « Canon EOS 7D Master thread »
