Om DU Patrick vill lära dig något om hur en rawkonverterare fungerar så läs detta.Läs sista punkten.
Återkom gärna med frågor om du inte förstår nedan
• White balance. The white balance setting on the camera has no effect whatsoever on the
captured pixels when you shoot raw—it’s simply recorded as a metadata tag in the raw file.
Some raw converters can read this tag and apply it as the default white balance (which the user
can then override if desired), while others may ignore it completely and analyze the image to
determine white balance.
• Colorimetric interpretation. Each pixel in the raw file records a luminance value for either red,
green, or blue. But red, green, and blue are pretty vague terms—if you take a hundred people
and ask them to visualize “red,” you’d almost certainly see a hundred different shades of red if
you could read their minds.
Many different filter sets are in use with digital cameras. So the raw converter has to assign the
correct, specific color meanings to the “red,” “green,” and “blue” pixels, usually in a colorimet-
rically defined color space such as CIE XYZ, which is based directly on human color percep-
tion.
• Gamma correction. Digital raw captures have linear gamma (gamma 1.0), a very different tonal
response from that of either film or the human eye. So the raw converter applies gamma cor-
rection to redistribute the tonal information so that it corresponds more closely to the way our
eyes see light and shade. (This property of digital capture has important implications for expo-
sure settings when shooting, which I discuss in a paper called “Raw Capture, Linear Gamma
and Exposure”.)
• Noise reduction, antialiasing, and sharpening. Problems can arise with very small details in an
image. If the detail is only captured on a red-sensing pixel or a blue-sensing pixel, the raw con-
verter may have a hard time figuring out what color that pixel should really be. Simple demosa-
icing methods also don’t do a great job of maintaining edge detail, so most raw converters also
perform some combination of edge-detection and antialiasing to avoid color artifacts, noise
reduction, and sharpening.
All raw converters perform all of these tasks, but they may use very different algorithms to do
so
