September 6th, 2010, 02:02 PM
Originally Posted by jambaj0e
Quick question with using flash:
As an intermediate level user, I've been fairly successful with using manual mode to get proper exposure without flash, but I'm having trouble trying to figure out how to calibrate shutter speeds when I'm using flash. How do I know how fast I can use the shutter speed at any given f-stop when using flash, since the exposure meter doesn't reflect actual exposure when using flash?
Does the flash have an "auto eye"?
If it does, the flash will have a few "Auto f/stop" choices to pick from. Like f/4, f/5.6, f/8, f/11... it will at least have 2 anyway...
Set the flash on an "auto f/stop" and then use that f/stop on the lens. The fastest shutter Shutter speed will be what the manual says you can use... 1/160 is common. Make sure to look on the flash for the near/far distance at the f/stop your using.
- Side Note: Slower Shutter Speeds will effect how bright the background can get, the subject exposure won't change. This is called "dragging the shutter", Outdoors, this will allow a normal background that is not too dark.
This is the easiest way.....
For a full manual flash with no guide, you need to know the power output..(Guide Number) example: GN 100 at 10 feet.....
- Focus on your subject
- use this formula.... GN-100 / #feet = f/stop... the pink 100 an example, use the guide number from your flash
GN100 / 10feet = f/10
GN100 / 6 feet = f/16.5
GN100 / 16 feet = f/5.6 (about) f/7.2 may be better (f/6.2 is the actual f/stop, but no camera has that setting)
GN100 / 25 feet = f/4
Set the Lens to your answer, or closest f/stop to the answer.
Last edited by G1 User; September 13th, 2010 at 07:45 PM.