Prince Cheap Here Again!
"I'm starting out and I don't know how much power I need…" someone recently said to me.
So, I just asked them a question right back. What type of images are you creating? The person said, "…Headshots, family portraits, actors, models, my teacher, mars and my mother…everything!" I responded, "Ooooooookaaaaay, you gotta figure out what you wanna photograph then set your power accordingly to the size of your subject. So get the most flash you can afford, then you'll be able to do power modifications to use that power monster in whatever your situation."
This article is designed to help you to start thinking about what you need and more importantly what you can do with what you have.
Rule number one for beginning photographers out there - get educated: Listen to the first LightSource podcast interview with Paul C. Buff of White Lightning & Alien Bees. There you'll learn about starting out with studio lighting and "power". Trust me… the last 20 minutes of this interview will absolutely make you think differently about what you "need".
School photography classes usually have the most powerful everything and it often handicaps photographers because they start out with the best equipment. The best things on earth have all come out of someone needing something and finding a way to do it! Photography is no different.
How can I possibly have any problems when I have a high power flash? A lot of photographers like the one I spoke with find themselves in this position after making their first strobe purchase because they purchased more light than they really needed. Think about this: you have a strobe that is 300 watt-seconds illuminating portraits of 1-2 people in your garage or home studio. You will find yourself turning its power all the way down and it still may be too bright for what you want. Then what do you do?
Option number one: You dial your cameras aperture down. Problem? The depth of field of your image drastically increases. You may not want that in every case.
Option number two: Back your light source up. This will reduce the amount of light that actually strikes your subject. However, this makes your light source smaller (not physically but visually - just think about the sun… its millions of times larger than the earth, but being so far away its only a tiny blip in the sky!). Smaller light sources create harsh light with very strong shadows. See this article about distance to subject and relative size.
Option number three: This option is my particular favorite. You could use some neutral density gel over your light source to reduce the light output. If you don't have access to gels, you can use black tulle fabric to do the same job. It is sometimes hard to work with but it gets the job done!
Here's the point: You CAN have too much light. When you do, you will have to spend some thought on how to reduce it (But the truth is better have and not need than need and not have!). This situation is when low power Britek PS-200H, Alien Bee AB160, Calumet Travelight 125 and other flashes below 200 watt-seconds come running to the rescue. These strobes, and many others, have very low maximum power output levels. This low power option can make running a home studio much easier!
Take this home studio portrait for example - I used was a 125 watt El Cheapo Britek PS-200H flash bare bulb inside of a 60 inch Westcott Optical White Satin Shoot Thru Umbrella. The light was placed four feet away on the camera's left side (set to half power). The camera was set to F4.5, 1/125th, for ISO 100. There was a gold reflector duct taped to a light stand about 3 ft away on the camera's right side. Now I was photographing in the space of a tight living room filled with furniture.
If I had a light source of 300 watt-seconds which could not reduce its power down to about 1/8 power, 9 times out of 10 the image would not have the "pop" it does because I would not be able to use the F4.5 wide aperture! Now remember, there are many reasons to use high power strobes. But for most people portraits the truth is… you don't need much more than 100 watt-seconds of output.
You can do wonders with low power strobes. They are very powerful when you know how to use that power. As for our original question, 'how much power do you need', it still depends on the size of your subject and the quality of light you want. But for people portraiture, 100-160 watt-seconds can be effective. For more than five people I'd say you could get along with 300 watt-seconds effectively. In fact, a room full of people can be lit with a 125 watt-second light slamming into the ceiling. The light reflects off of it as nice as it would in a softbox or umbrella. Hint-Hint-Wink-Wink!
Take this food for thought and turn it into your attitude. You don't need one million watt-seconds to get the job done!