580exII Manual Settings

[acutshall]

I have used auto flash( camera manual mode) for some time and would like to start using manual flash.
Can anyone help me understand  the purpose of a couple of functions when using the Manual Mode  on the 580EXII


1. Zoom- I know this brings the bulb closer to or away from the lens, what is its real life purpose(situation). Does it help with diffusers?
2. Power level setting- again what is its real life purpose; is it the same as FEC in the auto mode. why is its settings in increments different than f stops or shutter s.

Thanks

[k bennett]

1. Zoom. This controls the spread of light from the flash. The numbers correspond to lens focal length, so 24mm is a wide beam spread, and 105mm is a tight spread. To see this in action, stand a few feet from a wall and shoot the flash at 1/64 power using different zoom settings. See the difference in how wide the flash pattern is.

2. Power. Manual is manual -- the flash *always* fires at the same power output every time. You have to set the appropriate aperture (and shutter speed) manually on the camera. You set the power level from full (1/1) down to 1/128 in 1/3's of a stop.

This is useful when you are using the flash off camera, possibly on a light stand with an umbrella. You set the appropriate flash power and manual camera settings, and the flash puts out the same amount of light every time.


You may be thinking of the original type of "Auto" flash, in which you set the flash and the camera to a particular aperture setting, and the flash varies the output to match the camera-to-subject distance. If you're going to do this, you might as well use the TTL system, setting the camera to your chosen aperture. The flash will vary the output to match your aperture (within limits).

[acutshall]

1. Zoom. This controls the spread of light from the flash. The numbers correspond to lens focal length, so 24mm is a wide beam spread, and 105mm is a tight spread. To see this in action, stand a few feet from a wall and shoot the flash at 1/64 power using different zoom settings. See the difference in how wide the flash pattern is.

So should I try and match the focal length of my zoom?

2. Power. Manual is manual -- the flash *always* fires at the same power output every time. You have to set the appropriate aperture (and shutter speed) manually on the camera. You set the power level from full (1/1) down to 1/128 in 1/3's of a stop.

This is useful when you are using the flash off camera, possibly on a light stand with an umbrella. You set the appropriate flash power and manual camera settings, and the flash puts out the same amount of light every time.

So does it act like FEC in Auto Mode(Flash Unit)  in that you can reduce light exposure output i.e if you are trying to create a lighting ratio or a fill flash stop difference?

When using a diffuser (1-1/2 stop difference) which one of these would need to be adjusted to compensate

Thanks