Flash drag

I have been reading on the various techniques for dragging the shutter, and

most advise states to set the flash for the aperature and the shutter for

ambient light (okay..that is in a nutshell). Will it work out for me if I set

my flash to ttl, stop it down about 2/3, and then just meter for ambient light

and set my camera exposure for the reading? Thanks

No. The point is to underexpose the ambient in relation to the flash exposure. The flash exposure should be "normal"--whatever gives you good exposure (not underexposed, not overexposed) on the subject. Here is the procedure in a nutshell. Meter the ambient exposure for the f stop you want to use, chosen for the DOF you want. Set your f stop. Set your shutter speed for at least two stops faster than your ambient reading. Use the flash--manual, auto thyrsitor, TTL, bounced, modified, whatever--doesn't matter--so it gives correct exposure for the subject. You may have to increase your shutter speed so you can stop motion better, especially if the subject is moving fast. Keep tabs of the flash exposure and compensate accordingly. If the flash underexposes, you can begin to get motion blur.

I should add--you can sometimes expose for the ambient without underexposing, but that is usually if you are on a tripod and your subject isn't moving. If you don't underexpose the ambient, your any subject motion and handholding motion will show. The flash duration is what freezes the subject in these kinds of shots.

Some reading for you.

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00LX12

Dragging the shutter, is simply a way to include the ambient by means of the shutters speed in combination with the aperture being wide enough for the speed (or stopped down as the case may be). Then set the flash to >>> on the flash's setting and I normally use - 1/3 comp on the flash as the camera takes over if the comp dial is at 0 on the flash.

 

So, set the shutter speed for about 1/15th sec and then set the aperture to allow for a negative ambient exposure (I like to dial this in to expose about -1.3 stops). Now set your flash on ettl and the >>> setting, then dial the flash exposure up or down by 1/3rd and play.

 

Hope that offers some simple working example to get going with.

I am assuming, in my response, that you intend to use the method in low lit reception type scenario's and create some light trails.

 

If not that intention, then Nadine is giving you the method that will result in the correct DOF but NOT to slow the shutter to the point of light trails. So, it would depend on your needs.