A general scare exists among photographers at any photo studio about lighting, but in fact there is no mystery about it. There exist two aspects of it: exposure and shadows. Of course, there are more things to it that need to be taken into consideration like color, composition, background, makeup and hair if it is shooting a model.
In the studio, special attention needs to be paid to the exposure relationships between the different light sources, which is expressed as ratios and determine the places where it needs to be placed to make the subject look good. Here comes the role of shadows.
Lighting Ratios: If light is placed in front of a model directly, there is no need to consider about ratio. The exposure is straightforward. To set up the image, a meter could be used in incident mode and the metered reading taken.
With two lights, the input can be varied (hence the exposure) with each of it by changing the distance between the subject and the source and also making changes to the power setting. With light ratio of 2:1, the difference between the main light and the fill light is one f-stop.
For a 3:1 lighting ratio, there are one and a half f-stops of discrepancy between the two sources. Digital cameras use 1/3 f-stop increments to measure light, though the 3:1 ratio as was used traditionally is taken with half f-stops.
Due to the ability of sophisticated handheld light meters to read light in tenths of an f-stop, one can easily determine one and a half f-stops if there is a requirement of such ratio.
The positioning of a handheld meter helps in precisely measuring the light on a product of face and is a great advantage to the photographer. By measuring a reading from the position of the subject after pointing the meter’s white dome toward the primary light source, the correct exposure can be determined for the main source.
Then on removing the white dome away from the main light projecting toward the fill, a precise reading on a fill light could be taken. By taking note of the f-stop readouts as given on the LCD and making adjustment to the light, the ratio could be found that will help in making the subject look in the way that is needed. It is not always necessary that studio lighting is taken in the studio itself. The outdoor location could be turned into a studio.