Flash Power

Flash Power

The fourth variable of flash exposure is called Flash Power.

Flash Power is exactly what it sounds like: The Power of your Flash!

The higher your flash power is set to, the more light will be emitted from your flash. The lower your flash power is set to, the less light will be emitted from your flash. The flash power only affects your flash exposure.

One of the most frequent questions I get on flash power is how to know what to set your flash to. I always associate my flash power to my aperture and ISO settings. I like to think of my aperture like a wall that my flash power has to break through. The smaller my aperture is set to, the more power I'm going to need to break through that wall. The wider my aperture is set to, the less power I'm going to need to break through that wall.

Almost all of my flash photography starts off with an available light decision first. I think of what I want my available light to do and then I worry about the flash exposure. For example, let's say that I am in bright available light conditions and I want to kill all of my available light in a shot. I know I'm going to need to set my shutter speed at it's max sync speed to get rid of as much available light as possible. My ISO is going to be set to the lowest setting, since I want the least sensitivity to light possible. My aperture is going to control the last bits of left over available light that my shutter speed and ISO can't control because of limitations. The shutter speed with it's max sync speed, and the ISO with the lowest possible setting. The aperture comes into play and has to be closed down. The more I have to close down my aperture, the more flash power I'm going to need to break through the "wall". So based on my aperture setting I'm going to set my flash power. A small aperture is going to require a higher flash power. A larger aperture is going to require less flash power.

The wall analogy really helps me in understanding my flash power setting. Just remember, a larger aperture requires less flash power and a smaller aperture requires more flash power!