Off Camera Flash And One Light Portraits.

I've been getting into off camera flash photos lately. It's a crazy, confusing and intimidating topic. All this talk of ratios, flash power, stops of light, the inverse square law and everything else is very confusing at first. Note I said at first because once you get it, it all falls into place.

I was quite thrown by the concept that your shutter speed controls the ambient light level in the scene and the aperture controls your flash exposure. I said "What the hell does that mean". I remember losing 10 more hairs over that one. Haha.

Then it hit me, of course that makes sense. The ambient is controlled by the shutter speed. Just like with available light photography, the longer you expose, the more light you get. That made sense to me but what does it mean when we hear that the aperture controls the flash exposure? Well, the duration of a flash pop is very, very short indeed so the exposure of it would not be affected by the length of the exposure. The aperture would make a difference there by letting more of that short duration light enter the camera for the exposure. Ok. That started to make sense to me now.

Flash power and stops of light are the same. As you turn the power down on the flash from Full to 1/2 to 1/4 to 1/16 to 1/32 well those are each a stop of light. My light bulb went on there. Combine that with ISO and Aperture and we can move the light all over the place to get the exposure level we want.

Now what is this inverse square law? In a nut shell the inverse square law says is that an object that is twice the distance from a point source of light will receive a quarter of the illumination. Hmm. I still say WHAT?! So I found an explanation by Geoff Lawrence that makes sense to me. But, even understanding it I really didn't know why I needed it. Then I borrowed Zack Arias's OneLight Workshop dvd from a friend and he explained how the law affects the contrast ratio from one side of the photo to the other. Not a big deal if you only have one person but a big deal if you have more. I will not even attempt to explain that yet but the farther you have your light source away from the subjects, the less the contrast from side to side is but the light level is also lower. I'll deal with that more when I start lighting more than one person at a time.

So, now that I am gaining more of an understanding of how this all works, I started to take some experimental shots. I decided to not even try to get the ambient in the photo as it's more to worry about. Instead, I decided to kill it with a very fast shutter speed. I went to the maximum sync speed of my Canon 50D. 1/250 of a second. In my basement that killed the low light so all I had to worry about was the flash exposure. Here are a couple of experimental photos I did which I have already posted elsewhere on this blog but will reuse for the sake of this post.

All the light in both of these photos came from my Canon 430ex flash reflected by my 46" convertible umbrella, my new favorite toy. One thing I really like about reflecting the light into the umbrella is that it spreads it out quite a bit and will wrap around your subject. I used only the one light source here. No fill at all. I'm quite happy with the results. I can't wait to work on some more.

Chris.