David SL
Veteran Member
I'll just add to some of what you provided.
First, accurate exposure places the relative luminosity of all the hue elements in the image right inside the range of the available dynamic range of the sensor. So think of this as what an artist does when he/she selects the colors that will go in his/her palette prior to starting a painting, if the artist is doing a portrait and chooses colors in the green range for his available palette slots, nothing about the skill of the painter can recover a color "balanced" painting from that palette. (he/she would have to remove some green and add flesh oriented hue's to be able to paint a life like shot) The analogy breaks down in that a real artist can add black and white to their palette and create enough contrast in the greenish tones through mixing to create similar colors with different luminosity, but still the number of mixed splotches on the palette is limited to its size(number of slots).
The contrast setting is intimately tied to exposure, it tells how much importance to give to dark or light values per pixel. If contrast is high the slots tend to be filled with a sampling of hues across the range available from the gamut. (Which usually yields sudden transitions in hue and luminosity) If contrast is low, an attempt is made to represent as many hues in the scene as possible that can be represented by the gamut. (which usually yields "flat" looking images but retain detail in transitions)
The camera does not distinguish between luminosity and chrominance, some colors are brighter than others but the fixed dynamic range of the sensor can only accomodate so many values. This makes it important to get the relative luminosity of pixels in the image near enough to the actual luminosity presented in the scene, it increases the likelyhood you can extract a [more]balanced image in post processing. If you choose the wrong exposure, say too dark or too light you are saying to the camera "use your dynamic range to represent what I am showing you", if you severely underexposed the image the camera will oblige by filling it's slots with dark hues, if you overexposed it will fill the slots with light hues. Either way, you have precious few slots remaining to hold hues that were important to the scene being visaged but not considered by the exposure and consequently have less or no leeway for recovering the relative proportion of those hues (many will be missing outright) in the image in post processing.
The user defined WB setting basically allows the real world hue values represented by the sensor to fit neatly into the dynamic range of the sensor. It tells the camera "the colors in the scene are in this general hue range, fill your slots with colors from this range". Note the actual colors selected come from the specified gamut or color space, the gamut is much larger than the number of available slots!(the dynamic range) Just as an artists palette is restricted in physical size and this restricts the number of inks he/she can choose to include on that palette but not the actual ink which is restricted by the gamut. Note if your scene includes colors that your gamut doesn't map then you may get clipping or posterization in the affected color channel. For example, using sRGB for landscapes to shoot portraits will not optimize use of the cameras dynamic range, since you'll be starting with a set of inks (back to artist analogy) that don't match well the colors that exist(flesh tones) in the scene you'd like to represent. Can the image come out fine, sure outwardly, but if you are pushed to the limits of post processing the bad choice of gamut for the imaged scene may restrict your ability to optimize the image.
[continued: next post]
Okay this is where dynamic range comes into play, basically the dynamic range of the image tells you how many fine slots for color the image is capable*(note that doesn't mean that it actually uses all the slots for distinct colors!) of retaining. Slots for colors and actual number of colors representable (the gamut) in the scene are two different things. This is a subtle difference between dynamic range and the color gamut of the image (such as sRGB or AdobeRGB) but one that we must understand to figure out why getting image attributes like exposure (obviously) and white balance(most importantly) accurate in the body is important even when shooting NEF.
First, accurate exposure places the relative luminosity of all the hue elements in the image right inside the range of the available dynamic range of the sensor. So think of this as what an artist does when he/she selects the colors that will go in his/her palette prior to starting a painting, if the artist is doing a portrait and chooses colors in the green range for his available palette slots, nothing about the skill of the painter can recover a color "balanced" painting from that palette. (he/she would have to remove some green and add flesh oriented hue's to be able to paint a life like shot) The analogy breaks down in that a real artist can add black and white to their palette and create enough contrast in the greenish tones through mixing to create similar colors with different luminosity, but still the number of mixed splotches on the palette is limited to its size(number of slots).
The contrast setting is intimately tied to exposure, it tells how much importance to give to dark or light values per pixel. If contrast is high the slots tend to be filled with a sampling of hues across the range available from the gamut. (Which usually yields sudden transitions in hue and luminosity) If contrast is low, an attempt is made to represent as many hues in the scene as possible that can be represented by the gamut. (which usually yields "flat" looking images but retain detail in transitions)
The camera does not distinguish between luminosity and chrominance, some colors are brighter than others but the fixed dynamic range of the sensor can only accomodate so many values. This makes it important to get the relative luminosity of pixels in the image near enough to the actual luminosity presented in the scene, it increases the likelyhood you can extract a [more]balanced image in post processing. If you choose the wrong exposure, say too dark or too light you are saying to the camera "use your dynamic range to represent what I am showing you", if you severely underexposed the image the camera will oblige by filling it's slots with dark hues, if you overexposed it will fill the slots with light hues. Either way, you have precious few slots remaining to hold hues that were important to the scene being visaged but not considered by the exposure and consequently have less or no leeway for recovering the relative proportion of those hues (many will be missing outright) in the image in post processing.
The user defined WB setting basically allows the real world hue values represented by the sensor to fit neatly into the dynamic range of the sensor. It tells the camera "the colors in the scene are in this general hue range, fill your slots with colors from this range". Note the actual colors selected come from the specified gamut or color space, the gamut is much larger than the number of available slots!(the dynamic range) Just as an artists palette is restricted in physical size and this restricts the number of inks he/she can choose to include on that palette but not the actual ink which is restricted by the gamut. Note if your scene includes colors that your gamut doesn't map then you may get clipping or posterization in the affected color channel. For example, using sRGB for landscapes to shoot portraits will not optimize use of the cameras dynamic range, since you'll be starting with a set of inks (back to artist analogy) that don't match well the colors that exist(flesh tones) in the scene you'd like to represent. Can the image come out fine, sure outwardly, but if you are pushed to the limits of post processing the bad choice of gamut for the imaged scene may restrict your ability to optimize the image.
[continued: next post]
