Question about phosphors

[earlyfilm]

Originally Posted by old_tv_nut

1) You mean increase the density of the blue filter (make it darker).

Yippes!

With hoof in mouth, I wrote "Density" when I thought "saturation", ie., to allow the blue filter to pass more non-blue light which is yellow light.

Actually more density would also work, but again it would be counterproductive in getting a brighter screen image.

Adding density to blue is exactly what a yellow filter would do. Block some blue light, but allow red and green to pass light mostly untouched.

Allowing the blue filter to pass some yellow will ever so slightly reduce the flicker withut hurting overall color saturation.

When the color wheel is there, you simply want to get more light on the screen.

I assume the use of "density" by a non-specialized-in-photography author may mean "saturation" as in the terms are sometimes used interchangably.

James

[stromberg6]

CBS used a P-6 phosphor in some of their tubes. It glowed white, as opposed to P-4, which could have varying mixtures of blueish or yellowish phosphors. The CRT in my GE 810 is a 10FP4A, which is very close to "pure" black and white, with sharp contrast.

[old_tv_nut]

Originally Posted by earlyfilm

Yippes!

With hoof in mouth, I wrote "Density" when I thought "saturation", ie., to allow the blue filter to pass more non-blue light which is yellow light.

Allowing the blue filter to pass some yellow will ever so slightly reduce the flicker withut hurting overall color saturation.

James

I'm afraid that allowing the blue filter to pass enough yellow to get a better white would affect the blue saturation significantly (and the magenta also), However, if you are starting from the very dark and saturated blue of the wratten filter, reducing the saturation is exactly what CBS did to get their lower-flicker primaries, so in that case I agree with this strategy - but it really did desaturate the blues and magentas compared to NTSC.