Navigating the Studio Lighting Maze
Some photographers think studio lighting is too complicated and too expensive but in reality it can be neither. Part of this misunderstanding is created by seemingly bewildering array of product types and their buzzwords. To help you navigate the maze here’s a look at Studio Lighting 101.
Today’s Post by Joe Farace
One measurement of a digital camera’s resolution is megapixels. Purists may prefer to know the details, such as 18 mm × 13.5 mm. studio electronic flash output, on the other hand, is typically measured in Watt-seconds, which is a unit of electrical energy that’s equal to the work done when a one ampere current passes through a resistance of one ohm for one second. (That really helps a lot but keep in mind we all know what horsepower ratings are but what is a horsepower?) Sometimes a Joule is used as way to measure the power of an electronic flash’s power supply but because Ws doesn’t consider the light’s reflector design in it’s measurement, so it’s not perfect. That’s why you will occasionally see Effective Watt-seconds, made popular by Paul C Buff, used a method of power measurement.
A Lumen is a unit of measurement of light intensity falling on a surface. A lumensecond refers to a light of one Lumen for a one second or the equivalent, such as two Lumens for half a second. The number of lumenseconds produced by a flash depends on how effectively the flash turns electrical energy into Ws into lumenseconds. Most electronic flash units produce between 15 to 50 lumenseconds per Ws and sometimes an efficient 300 Ws system produces as much light as an inefficient system rated at 1000 Ws.
Some people prefer to use Guide Number (GN) to measure flash output because it considers the entire lighting package. Guide Numbers are quoted in feet or meters and are valid for a given ISO setting. The higher the guide number, the more the light output. Guide numbers can also serve as a way to calculate aperture when shooting without a flash meter. To determine the correct aperture, you divide the guide number by the distance from the flash to the subject.
Finally, all light behaves in accordance with the Inverse Square Rule that states that light’s intensity decreases by the square of the distance from the subject or more simply that light gradually falls off if the light source is far from the subject and increases rapidly if the light source is closer to the subject. You don’t have to be Stephen Hawking to figure that out but this can have an impact on the quality of light too. Because the other half of the equation is that the closer a light source is to a subject, the softer it is and conversely, the farther away a light source is the harder it is. (Size also matters and we’ll beat that poor horse dead in an upcoming post.
