The picture above was taken at CALTrans’s traffic monitoring center (California Transportation).Using at 28mm lens, I metered the scene, decided on ISO 400, 1/8 sec @ f11. The flash that’s hidden between the monitor was set to give me f11. It was triggered by wireless Quantum radio slave.
The Olâ€™ Control Room/Nerve Center
The picture above of a control room is fairly common these days. Gone are the old chalkboards and other â€œanalogâ€ displays, this picture could be the setting for a casino’s security center, or any hub for communication.
In this situation, Â camera shake will be a factor because you will have to use a slow shutter speed to allow the lighting in the room to â€œburn inâ€ or record on your camera’s sensors.
So it might be a good idea to bring along a tripod. I keep one in the trunk all the time just for this types of situations.
I filled the frame (viewfinder) with one of the displays in the scene to see what the exposure needed to be.
I chose monitor which had the most dominant image in the room.
I fired off a frame or 2 @ ISO 100 1/2 sec @ f11 and checked the LCD monitor or as we photojournalists say â€œchimpedâ€
I made sure the colored lights had good saturation. Over exposing will cause the colors and the image on the monitors in the scene Â to be washed out.
Then it was it was time to check the Guide Number of my flash.
Guide number for flash units are always given in metric and feet.
For my purposes, since I’m in the US,Â Iâ€™ll be concerned with the bottom number in each cell in feet.
Guide Number =Â Aperture x Flash-to-subject distance.
Iâ€™m estimating that my flash placed between the 2 monitors is roughlyÂ 5 feet away from my subject.
So the Guide Number Iâ€™m looking for is close to 11 x 5 i.e. 55.
I can see under Flash Coverage between 50 mm and 70 mm I comeÂ Â closest number to GN 55.
Now I can read across to the left and see that I have to set my flash to approximately 50 mm setting at 1/8th power.
If your flash has no ability to zoom in and out, then you have one less variable to worry about. That just narrows or widens the beam of light that comes from your flash.
You might be thinking this is a whole lot of Math. It isn’t if you are using your equipment daily or often.
**Make a copy of your flash unit’s Guide Number chart and tape it to your flash. Setting your flash manually has the added advantage that it doesn’t shut off prematurely because it doesn’t care how dark or light your subject is.Â Â Â
When you use Auto, the flash may be â€œfooledâ€ when it hits something reflective.**
Coming up next will be how to use 2 light to make your subject â€œpopâ€ in location lighting.