Why did 405 look so good?

[ppppenguin]

Having used scopes to view video (mainly 625) on 20us/div, 10us/div and 5us/div over many years and more times than I've likely had hot dinners I can't say I've noticed any difference in trace brightness between those settings. There may have been differences which I didn't notice but there's certainly nothing gross. Similarly viewing whole fields of video at 2ms/div isn't very different in brightness either. The time things get dim are when the duty cycle goes down, such as strobing a single line out of 625.

Specialist TV waveform monitors usually automatically increase the brightness when strobing out single lines. Even then it's still nowhere near as bright as viewing all the lines.

But this is a very different question to the 405/625 conundrum.