The Filters We Need With Digital...

Started Oct 5, 2008 | Discussions thread
JensR Forum Pro • Posts: 17,946
On the 80A

Two - The 80A "Color Balancing" Filter
Most cameras have sensors that are "daylight balanced". They have
nice, balanced red, green, and blue channel responses in neutral
colored scenes lit by daylight. They achieve their incandescent white
balance by amplifying the blue channel over two full stops relative
to the red channel. That adds a great deal of noise to the blue
channel, so you see some pretty ugly shadows. It also makes it very
easy to blow the red channel, especially when shooting red dominated
subjects (human skin, cosmetics, and fall colors near dusk and dawn
when the light is warm).

So, let me see if I got this straightly.

What the 80A does is basically that it lets less of the R and G channels pass, thereby increasing the percentage of the B channel to a "balanced" mix.

So, instead of pushing only the blue channel, we now push all of them. Which means: Use longer exposure times at same ISO or higher ISO for same exposure time. Both options increase noise. Granted,they do so in all channels. I can imagine that this sometimes is beneficial, but it's no free lunch. Or is it?


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