You're thinking of this in the wrong terms Chez. If the flash is set on max sync speed it
will sync with any shutter speed all the way down to long time exposures in the sense that the flash will occur while the shutter is fully open. It wouldn't be much use to you though. The idea is to be able to use the flash balanced with ambient light to provide
fill flash - just enough flash to brighten the subject and lighten the shadows, allowing the ambient light to be the main source of illumination. We do that by first taking an exposure meter reading in the usual way. Say your indoor reading is 1/60th at f8. If you use Shutter Priority Mode (which I find easiest for this technique) then simply set your shutter speed to 1/60th and the flash will adjust it's output for those settings resulting in a shot nicely balanced between flash and ambient light. The other way of course is to use Manual Mode, set 1/60th at f8 and again the flash will adjust it's output to those settings.
This is often referred to as 'Slow Flash Sync' You don't know how lucky you are - prior to TTL metering, you could only achieve fill flash with a focal plane shutter(which all SLRs have) by dividing the aperture you wanted to use into the flash guide no. which gave you the distance you
had to take your shot from, OR divide the distance at which you wanted to shoot into the guide number, which gave you the aperture you
had to use. Modern cameras and flashguns have made what used to be a PITA into a simple process.
Another use for it is imagine it's evening and a beautiful sunset. You want to photograph your signicant other with the sunset as a backdrop. Your normal choices would be an available light shot which would be great for the sky but leave your other half as a silhoutte, OR use flash which would be great for 'er indoors, but the exposure would be far too short for the sunset and you'd end up with an under-exposed black background.
Take a normal meter reading for the sunset - say it's 1/20th at f8. Now set your camera to those settings as described. You'll have to tell her (or him
) to keep reasonably still with a shutter speed that slow, but your camera makes the correct exposure for the sunset, and during the exposure the flash fires just strongly enough to light up your foreground figure.... Voila!
What you need to do is some quick practice shots indoors under room lighting to see what a huge difference this makes to your shots,
Hope that helps Chez. Sing out if not.