On Fri, 2 Jan 2004, frank theriault wrote: > What's trailing-curtain-sync? I've heard the term, but have no idea > what it is (other than what Paul just said about shooting slower than > max-sync speed).
The two terms (leading versus trailing curtain sync) refer to whether the flash fires at the beginning or end of the exposure. Leading curtain sync fires at the beginning; trailing, at the end. That option exists because flash at the start of a longish exposure often looks unnatural. Imagine a flash-lit shot of a person walking in a dark room, but with a 1 second shutter speed to expose for the background. If the flash fires at the beginning of the exposure, you'll have a perfectly frozen person with a blurry motion trail leading out in front of them, which looks pretty crazy. If you use trailing curtain sync, then the flash fires at the end of the 1 second exposure, leaving you with a nice blurry trail leading up to a flash-frozen person, which looks more normal. If you imagine the same thing with a car, leading curtain sync will extend the headlights out in front of the car, while trailing curtain sync will leave the headlights looking like a trail extending behind the moving car. This principle works for faster shutter speeds, too, although it's not always as noticeable. Flash has a duration of around 1/10,000 of a second, IIRC. chris
