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Subject: Re: raw 3.1 professional custom profiles for highend digital cameras



As Jeff said, it's a type thing, not a brand thing.

Metering for Zone V was OK with film, because Zone V was squarely in the middle of film's tone curve.

DSLRs don't have that highlight compression, and Zone V is way down around 50 or so on a 0-255 scale. Fully half the data the camera captures is devoted to describing the brightest f-stop the camera can record at the selected exposure/ISO settings. If you underexpose, and hence fail to populate that range with captured data, you're only capturing half the tones the camera can record, and you'll be fighting posterization and banding when you try to redistribute the captured data across the whole tonal range.

You're always going to get better results with digital capture when you stretch the highlights, darkening the midtones and shadows, than you will by compressing the highlights and lightening the midtones and shadows, because the camera captures much more highlight detail than we can see, and much less shadow detail than we can see.

Within limits, digital raw give you a huge degree of latitude in where you place the midtone, but those limits are imposed by where you set the highlight point. Everything hangs off the highlights, so the key decision you need to make when exposing for digital capture is where you want to set your highlight point. That's why I spot-meter on the highlights.

The tone response of the sensor medium is the biggest and most confusing difference between film and digital. Film behaves approximately like eyeballs. Digital capture doesn't, not even vaguely. A useful exercise in trying to get your head around this—at least it helped me a lot, is to make a linear-gamma grayscale gradient, and watch what happens as you shove the bits around to try to make it approximately perceptually uniform.

Digital isn't panchromatic either—it's way more sensitive to red and IR than it is to blue and UV—basically the opposite of film—but that's a much smaller issue than the difference between a perceptually-weighted response and a linear one.

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