Flash and Lighting
I have written a bit about flash before (see links at bottom) but people on the Alpha flickr group wanted to know some more. So I’m just going to start blabbering and see where this goes :). People seem to use very technical terms when it comes to lighting like – “big” and “little”. Sounds simple enough but what does it mean? Can I make a big light small and a small light big? How will it affect my photos? does any one really care? …
The last question is the easiest, there is so much literature on the subject some one must give a hoot :). I bet your local library has several books on the subject so why not have a look? Light: Science & Magic ISBN-10: 0240808193 ISBN-13: 978-0240808192 is my fave. It can get a bit technical but it has lots of good info.
Size is IMPORTANT
Sorry guys, size is important. Many will tell you the bigger the better but that’s only a 1/2 truth, as we need small lights as well. But its normally easier to turn a big light into a small light than the other way around. So basically yes bigger the better, but not all the time.
To determine the size of a light source you need to know how bright it is, how far away from the subject it is and how big is the subject in relation to the light source. e.g Our sun appears as a large light source covering one whole side of the world in light, but its actually very small compared to other stars. Because the other stars are so far away from the earth, they only appear as tiny points of light in the sky, even though in reality they may be many times physically larger than our sun . The exact same thing is true with our flash/lights in photography. If the brightness of my light source remains the same but I move it closer or further away from the subject the “apparent size” of my light will change.
Its all relative
There is more to the size of my light than the distance to my subject e.g. If I light a matchbox toy car with a 60w household light bulb and the bulb is only a 15cm away from the toy car it will be a very large large light source in relation to the subject. Now if I hold the same bulb 15cm away from a real car my light source will be very small in relation to the subject.
The actual amount of light
The 3rd important factor in determining the size of my light is actually how bright it is. A 1000w studio flash will be able to provide me with a lot more light than a system flash with a guide number of 28. I can turn the power up and down on these flashes but the 1000w flash can simply provide me with guide number of around 95 @ iso 100 so its approximately 3.5 time more powerful, or a lot bigger.
OK, so that a basic bit about size. Next time I hope to talk about how the size of the light affects your photos highlight and shadows, and combining this information with light modifiers.