Keep It Main
The main light in digital photography lighting really just refers to the main light source. This means that the main light source is going to be the primary place that light comes from to illuminate the subject of your photograph. When we are talking about lighting for digital photography this will also mean that these can be specific types of artificial lights that you may be pulling out of a light kit and professional photography studio lighting equipment. Here is a look at the different main light sources that you can use to help enhance your photography.
Spot and Flood
Two of the types of main light sources are going to be the spot and flood, and these are available in all professional studio lighting equipment kits. The spot light is a direct light source that is much more intense and creates fast falloff. When you are using the spot light as a main light source you are going to have an image that is brightened very sharply, has less of it illuminated, and specific areas focused on. This is opposed to the flood light that brings a much broader light over the entire object. When the flood light is used as a main light this is going to change the character of the image as the lighting source is more egalitarian, the shadows are less harsh, and the area is going to be more evenly covered.
Reflection and Diffusion
A reflection, or bounced light, can be a useful main light. In this situation you are going to be using a reflective surface, which can range from a full service mirror to a simple white card, to reflect light onto the subject from a different light source that is producing the light. If you are using diffusion on the main light source then this essentially means that you are creating an intermediary between the light source and the subject.
This light diffusion is done be putting a cloth, a screen, or different types of surfaces that are designed to change the nature of the light. This will make the light much softer, the shadows less defined, and generally a less detailed image for the subject. This may also be done with the reflected light, but with both it is going to depend on the nature of the base light that you are using with it. If you are using a spot light with a reflective card then it still may be pretty strong, but if you are bouncing the light off of ambient light in the area then this is not going to create a very powerful light source.
The same is true with diffusion, and if you diffuse a fairly weak flood light then it will not be very sharp on the subject. When you are making these decisions in digital photography lighting you will want to decide ahead of time the general themes and perspectives you want your image to present so you can try to make sure that the lighting of the object reflects that. You are also going to find that these are part of the professional photography studio lighting equipment assortment.
The main light is going to be used in position along with other pieces of professional photography studio lighting equipment that will fill the gaps and complete the image. The fill light is going to come in from another comparable, and visible, angle to give a softer light. This is not going to define the shape of the image as the main light does, but it will fill in enough light so that it can be seen in an appropriate way according to the photographers wishes. The intensity and type of this will also depend on the decisions made around the main light. The intensity of all of these is also going to end up being a main deciding factor in how you set the aperture, ISO, and shutter speed, which is one of the primary negotiations in digital photography lighting.