Cross-polarization and dielectric specular

[sharktacos]

Fascinating stuff guys.

John, I'm reading in the course notes "dcraw seems to be the only software that conserves linearity, other software such as Adobe Camera Raw applies some gamma conversion and artistic tweaks." Does that mean that if one uses dcraw instead of Photoshop, then rawdigger becomes superfluous?

[joconnell]

Raw digger is more an examiner than a developer - you can measure your raw files pre and post debayering and it'll also make colour profiles for your camera based on arbitrary shots you take. It's a tool to let you see what your camera is doing and you can then use that data to make a better set of defaults for camera raw or photoshop to remove anything damaging.

[sharktacos]

Thanks, makes sense. Could you explain the importance of the Nuke script (or Photoshop actions) for calibrating the HDR as described in the course notes? I got a little lost, and you have a definite gift for explaining complex things in understandable ways

Also, have you used Lightzone? It's a GUI front-end for dcraw which is nice, but it's RAW convert options adds two new parameters: "color profile" (set to sRGB IEC61966-2.1) and "rendering intent" (defaults to "perceptual" but I changed it to "Absolute Colorimetric"). I wanted to make sure that these were correct to preserve linearity and such, so as to avoid the unwanted adjustments Adobe Camera Raw adds. I think that the color profile I selected is the one dcraw uses by default, but I'm concerned that "rendering intent" in particular will add automatic brightness correction, which I'd like to avoid. Here are the options:

Absolute Colorimetric
Leaves colors that fall inside the destination gamut unchanged. Out-of-gamut colors are clipped. No scaling of colors to the destination white point is performed. This intent tries to maintain color accuracy at the expense of preserving relationships between colors and is suitable for proofing to simulate the output of a particular device. This intent is particularly useful for previewing how paper color affects printed colors.

Relative Colorimetric
Compares the extreme highlight of the source color space to that of the destination color space and shifts all colors accordingly. Out-of-gamut colors are shifted to the closest reproducible color in the destination color space. This preserves more of the original colors in a photo than Perceptual. (See also Black point compensation.)

Perceptual
Tries to preserve the visual relationship between colors so it is perceived as natural to the human eye even though the color values themselves may change. This intent is suitable for photos with lots of out-of-gamut colors.

Of those choices, Absolute Colorimetric seemed the best, but I'm concerned about the "Out-of-gamut colors are clipped" part. It strikes me however that with most of the fronted GUI programs for dcraw, the user ends up needing to disable a lot of extra stuff, making the setup unnecessarily complex. What would be ideal is a GUI for dcraw that just did a simple conversion without adding in anything. because of that I'm leaning towards using a more bare-bones program like rawDrop. I just wish there was a mac version of it too.