Image by Zarek Tuszynski from Wikipedia I seem to have seen a lot of period dramas lately with photographers using flashbulbs like the one illustrated, most recently in last night's strangely low key Maigret . Many readers might be too old to remember these things, but when I first took photos as a boy we still used them. The bulb typically contains a magnesium filament, which burns out in a moment of glory. As it goes, it heats up the glass casing so much that it causes that familiar crunchy sound effect. So far, so good. But romantic though these old devices seem, they had one big problem - they were one shot (apart from the short-lived flashcubes etc., which were too small to be used by anyone but amateurs). So with a pro flashgun like the one in the image, the photographer had to get a handkerchief or something similar with which to remove the red-hot bulb, put the old bulb somewhere safe and insert a new bulb - a process that inevitably took several seconds. What I d...