Photography

Things nobody knows any more.

Incident light metering. The measurement of choice. It is a measurement of the light falling onto a subject, not that of the light reflected from it. You got an accurate exposure whether you were photographing snow or soot. My 1958 Rolleiflex could do it, my Weston could do it, my Lunapro could do it - even an ancient  Leningrad4 could do it. A cheap flashmeter can do it. 

Your super duper iPhone? Nope. 

Does it matter? No.

I voted Luddite at the last election.