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p.4 #4 · p.4 #4 · a850 vs a900, 1 stop better noise performance? | |
Thanks.I think I mostly understand what you said but a couple of questions:
What exactly does the CFA do and does it in reality provide more gradiant of tones in the green channel for the Sony camera (a900/a850) hence improving skin tones ?
From the comments it sounds like you favor the Sony over the canon; but at the same time suggest the cameras are more or less equal under good light. Am I miss-interpreting your comments or is it more along the lines that the canon (for example) will produce rich full colours but you have to work harder to obtain them ?
Also I've noticed a large uniformly of blue shift (when I talk about blue shift I'm focusing on skin tones) in many pictures displayed on the web from canon camera after the 20d (i.e, 40d,5dmk2, ...). It seems to my eyes that there is a bit of a blue overtone on the images. Now obviously this could be due to my monitor; due to these images being processed by a raw converter that shifts the colour (ala lightroom which is commonly used); my personal taste in images or something native to the canon camera. This does not seem to be the case with pentax or olympus pictures hence the question (you mentioned several times that Canon has problems with the shift from blue to red (ala purples); and so I wonder if that is related to what I am seeing or if I'm taking something totally unrelated and applying it to poor post processing or poorly calibrated monitor.
Also you point out that olympus and canon have very dense sensors but for full frame isn't Sony and Nikon denser than Canon ?
theSuede wrote:
Well, the digital communication lines out from the sensor in the D3x are only twelve lanes wide, just as the 850/900... And I seriously doubt they "hid" the missing two lanes somewhere else. There's a definite correlation between the slower read-out times 12>14bits and this. This is not 100% certain proof, but a very good indication.
The CFA's in the A850 and the A900 seem to be slightly different, but I've no hard data there yet. I have to take the time to go through the 850. This will be soon, as I'm personally interested in that camera. In fact the difference 900>850 seems to be about the same as the difference D3>D3s, with the D3s being (very) slightly better on all accounts.
you2:
Most cameras can be "good enough" with good light, and the right profile. Canon and Olympus have placed their level of acceptance slightly higher than some other players, both for the same reason - both the 4/3-system and the later Canons have a quite high MP/cm2 ratio. But for "normal" circumstances the problem is not as bad as it would seem, you only run into real-world, real-picture noticeable problems when shooting in "spiky" spectrum lights like fluorescents or sodium or stadium-type lights. Otherwise, no-one except the discriminating photographer who actually saw the scene in reality will notice any larger differences if you use the right camera profile for the situation (in my personal opinion). For higher ISO shots, the problems lies mainly with the blue primary, as that is highly dependent on the available surface fill factor.
You have to protect the silicon surface (as the pure silicon crystal is quite susceptible to chemical contamination), and the easiest way to do this is to oxidize the surface into SiO2 a few A deep, this is called the "passivation". You also have to insulate the areas around the lanes transporting charge in/out to the individual cells to keep them from contaminating the measurement. Both the insulation and the passivation are highly absorbant in the blue spectrum, so there is a considerable loss of blue Qe if you make the cell areas smaller. This is also why the noise on higher ISOs is mostly red/green - blues have long since vanished below the detection threshold, only thermal/read noise remains, almost no actual photon detection occurs.
Green has less problems with this, and long red passes through almost everything except the metal parts of the chip. Canon has expanded the blue response a bit to counteract this, but unfortunately this affects the blue-purple-red transition in a bad way. Trying to get the blue-to-purple shift just right in a Canon takes some serious work.
So, in good light with the right profile, any camera will do. A slightly "worse" camera will need a slightly "sharper" profile to be used for accurate correction, but it's definitely doable. The differences only surface when you get into "difficult" light, or less light. In my opinion, this is also why different raw-conversion engines work better with certain cameras, and worse with others - the algorithms that interpolate the two missing colours per pixel can use many different schemes of weighing luma/chroma (mis)information against eachother to get as close to reality as possible. And some schemes work better for some types of CFA compromises, worse for others....Show more →
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