Quote:
Originally Posted by Penthode
I recall however for 1970's studio cameras using plumbicon tubes, the noisiest color was blue. I think this was because blue is low luma and at the low (expanded) end of the gamma curve.
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The calculation of which saturated color will be noisiest is not simple. It depends on which color contributes most to luminance, among other things. On this basis, you might expect blue to be least noisy looking, but the problem was that the blue channel signal level was much lower than green or red under studio incandescent lighting. Because of this, the channel gains were set to give equal output on a white object under studio lighting with a clear filter in the optical path, and then an orange filter was rotated into place when doing outdoor pickups, where the signal level could be higher in all three channels.
I believe most up-to-date solid-state pickup cameras dispense with the filter change and use only electrical gain adjustments to get white balance. Blue is still the weakest channel under incandescent lighting, but gets a boost under daylight. This is certainly the case with DSLRs used for video, as well as stills.
The color splitting prisms in the Plumbicon cameras were designed in conjunction with the Plumbicon tube spectral responses and the assumption of incandescent light to give the lowest possible noise along with good color rendition, but it still resulted in the blue channel being much weaker than red or green.