By Derek Clark
What is TTL?
I’ll start part 2 (part 1 is HERE) by describing what TTL actually is. Feel free to skip this part if you already know this.
Back in the good old film days a lot of flash guns had a small calculator in the form of a chart or a small disk that rotated. These things basically calculated what setting worked for the Guide Number of the flash you were using. I had a Vivitar 283 back in the early 80′s, which was one of the most popular and reliable guns of it’s time. It had a dial built into the hinge of the bounce head (photo left). You set the dial to whatever ASA/Din number your film was (now called ISO) and the dial told you what distance you would cover with the varies apertures. The coloured sections corresponded to a dial on the…
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