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Regarding the brightness issue, a simple calculation shows:
Assuming
1) 100% collection of all the CRT light output (of course you can't),
2) a 5-inch CRT and a 50-inch picture;
that is an area ratio of 100 to 1.
In this overly optimistic case, to make a bright (50 ft-lambert) picture requires the image on the CRT to have a 5000 ft-lambert brightness, roughly equivalent to a sheet of paper in full sunlight. Any practical inefficiencies due to f-number of the optics, etc, either lowers the viewed brightness or requires a brighter CRT (The vertical directivity of the screen compensates this to some degree.)
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