Today's evocative photo shows Mulard Long Life picture tubes undergoing life tests at the Mitcham plant sometime in mid 1952.
On the test rig, applied voltages were regulated and the beam current was fixed. The test card used closely simulated a screen raster. Here we see Trevor Wibbley about to take voltage characteristc measurements, light output measurements and assess subjective picture quality.
What is special about the tubes pictured is that they were the first of those produced by Mullard with tinted glass faces. The tinting was introduced as an attempt to boost contrast when viewing in daylight conditions.due to the tinting agent cutting down reflected light hence making the black picture content appear much darker even though the tint did cut down the bright emitted light!