Though, as was mentioned, the flash's duration will be the shutterspeed for the flash exposure, you do have to check the ambient light levels, and make sure that the aperture-shutterspeed combinbation you set will render the bits exposed by ambient light the way you like them to be. (Because, opposed to what was suggested, ambient light levels do come into play even when not very bright.)
Originally Posted by mfratt
So it's a double job: both flash and ambient light exposures have to be checked and regulated.
You set the aperture to get the correct flash exposure, and use the shutterspeed to control the balance between flash and ambient light exposures.
The flash you mentioned is designed to interface with all sorts of automatic exposure functions on Canon EOS cameras.
Are you planning to use a Canon EOS camera with it?
If so, your camera may be able to do a bunch of the metering for you.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
Use a hand held meter with an invercone and point it at the lens , the flash is a constant so that will allow you to set the f stop then the shutter speed can be adjusted to control the ambient light .
"[H]ow exactly does one determine exposure...when shooting entirely analog"
It is the same with film and digital. (Why would it be different? We are talking only about light, not about cameras.) Incident flash meter is the most accurate way (and also usually the quickest). Guide numbers are another, but once you start adding modifiers, the amount of accuracy decreases (unless you have previously measured the effects of these modifiers with a flash meter...in which case you wouldn't need to be using guide numbers anyhow, because you have a flash meter).
When using flash, there are always two exposures being made at the same time for each shot; one is made with flash and one with ambient light. For the flash part, aperture controls your flash exposure. Flash duration (set by the manufacturer and usually not changeable) is the closest thing to shutter speed in this equation. However, though it does determine exposure length like shutter speed, it does not affect exposure itself except in cases of reciprocity failure in short exposures. As long as flash duration is shorter than the shutter speed, shutter speed does not affect flash exposure. (If flash duration is longer than the shutter speed, exposure is affected, but this generally only happens with flashbulbs, which have a longer duration than electronic flash.) For the ambient part, both aperture and shutter control your exposure, just as they always do without flash.
It follows that if you want to show as little ambient light as possible when shooting with flash, use the top flash synch speed when shooting. With a leaf shutter this is generally '400 or '500. With focal plane shutters, it ranges from '30 to '250 on most cameras. Blocking out the mild "leakage" that can occur is very important with color film, as every light source has a different color. It is important with b/w as well, but not nearly as noticeable.
Last edited by 2F/2F; 12-02-2010 at 02:03 AM. Click to view previous post history.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
- Rob Tyner (1944 - 1991)
Many modern digital meters (Sekonic L758, Gossen Starlite, Kenko KFM 2100) will tell you what proportion of the the reading taken is flash and how much is ambient light, they can even take 1 degree spot readings with flash. I don't own a digital camera, but the top of the range digital meters are magic.
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)