- The trial error path.
- The quick & accurate path.
The quick & accurate path: The Flash MeterA Flash Meter is not a new tool in the photographer’s quiver. As a matter of a fact, Flash/Light Meters were used at the beginning of the 20th century, and Don Norwood revolutionized the process with his incident light dome, the same used today. What is incident light? We call incident light, the light that is emitted by a light source and falls onto a subject (such as a model’s face). Inversely, one calls reflective light, the one being reflected off an illuminated surface (such as a model’s face). What is the difference between a flash meter and the camera’s built-in light meter? The primary function of a flash meter is to measure the incident light whereas your camera meter only does the reflective one. You might be thinking that the only exposure that is worth measuring is the one the camera will see and therefore the reflective light should be the one we should care the most. Well, it is not totally untrue, but one needs a way to measure the light in a constant fashion to then make a decision from it. It is because not all surfaces will reflect the light in the same way (dark skin, bright clothes…) that measuring the light based on its reflectiveness is far from being constantly accurate and useful.
How to use the Flash Meter?There is a wide variety of Flash Meter on the market but they all have the common basics: enable you to enter the ISO and get you the corresponding Aperture. What about the Shutter Speed then? Well as seen in the episode The Shutter in Flash Photography (shown in a Live Shoot) the Shutter Speed has no affect on the exposure of your subject when lit only by a Flash. So as long as your Flash Meter and Camera are set with the same ISO value then it will work. This is a picture of my Sekonic L-358 which is probably one of the most bought flash meter. Please note this Flash Meter does more than just measuring Flash light and we will see some of its complex features as we progress through Flash Photography.
Where to aim the Flash Meter?
People get always confused as to where aiming the Flash Meter. Some say “point it at the camera” others “point it at the flash”. So which one is it?
Well, it is quite simple really. If you want to measure the light emitted by your flash then, you need to point your Flash Meter at your Flash. If you wanted to measure the ambient light, then you simply aim it at your camera. Given we are in a studio setup and the ambient light will not be recorded, I only need to measure the light coming from the Flash. You may be thinking: ok but what if my model is not fully lit by the flash and a certain part of her body/face is in a less bright zone. Well, remember you always want to set your exposure for the highlights. The mid-tones and shadows are to do with ratio lighting which we will cover in a near future episode.
The under-the-chin rule
You may have heard that you need to measure the light from the chin of your subject. Well, it is not that strict. All you need is to measure the light from closest point of your subject to the Flash. Why? Because you do not want to take a measure under the chin if the light is coming from above and the forehead will most likely be more exposed to the light than the chin. Hence the chin rule is not carved in stone.
The sequence of steps
- Turn your Flash on, set it on manual mode and choose a power output value. I like to use 1/4 as it saves the battery and has a pretty good recycling time (time it takes the Flash to be ready for the next fire).
- Turn your Flash Meter on and set its ISO value to match the one set on your camera.
- Place the Flash Meter near your subject and aim it at your Flash.
- Somehow trigger the Flash Meter in combination with the Flash. Either use a PC cable to link the 2 or use a radio trigger as shown in the video.
- Read the F-stop value given by the Flash Meter.
- Use that F-Stop value (Flash Meter reading) and set your camera to the same value
- Change the Flash power output to enable your to get the Flash Meter reading to match the Aperture value you want with your camera. This can be also be achieved by changing the distance between your Flash and your subject.
- When your Flash Meter reading equal your desired Aperture value then take the shot.
- At this stage, your photograph might not be the most creative one but IT IS CORRECTLY EXPOSED!
- You keep shooting and make any modification you see fit. Remember as long as the distance between your Flash and your subject does not change and you do not alter your Flash power output, the exposure will remain the same.