Quote Originally Posted by roberttalbot View Post
Matt King,

Thanks for chiming in. "the right amount of flash that bounces back off the subject," learn something new every day.

So the aperture is the depth of field when using the flash unit just like without it. It's just the shutter speed is set to the side.

So the shutter speed is irrelevant and that is why it is set a 1/50s of a second. I wonder why they set it there, but that is going away from the topic if we tried to answer that.

The back of the flash does not give me the range of the flash but gives me the distance.

Matt, so my ISO is at 1600, I'm in a low light situation, I have the flash on TTL. The subject is 3.4 feet away from me -- yet the back of the flash stats f16, 23 feet. When I shoot the subject at 3.4 feet, I am wondering if it will give me a correct or right exposure of the subject.
I've now looked at the manual for the flash, so I can better help.

You first determine what aperture you intend to use. Than you set that aperture on both your camera lens and the flash.

When the flash is set to an ISO of 1600 and an aperture of f/16, the "23 feet" you see displayed is an indication of the expected maximum flash-to-subject distance you can expect to work with. Changing either the ISO or the aperture will affect that maximum, but the TTL circuitry in the flash and camera will automatically adjust the light output for shorter distances.

You can adjust the "f/16" by using the controls on the back of the flash. When you do, you will see that the "23 feet" will change.

Maximum range calculations are somewhat dependent on the scene - low, light coloured ceilings and reflecting floors and walls really assist a flash. A flash confirmation function is available on the flash.

Here is a link to the manual: http://www.summilux.net/documents/LeicaSF20.pdf

The pages are quite small, but they work with the zoom function.