Size and Distance of Lights in Macro Photography
Although a creative approach can usually overcome any lighting obstacles, in macro and close-up photography you’re typically working with subjects and scenes that are very small, and your camera tends to be fairly close to the action. These factors are important in determining which lighting equipment is most suitable.
Two main factors determine the quality of light that a specific source produces: its size and its distance from the subject. Here’s what this means:
A light source that’s larger than your subject causes light to come from various points, wrapping around the surface of the subject and so creating a soft light with gradual highlight to shadow areas.
A light source that’s small compared to the size of the subject produces a hard light, which originates from fewer points. This type of light creates shadows with defined edges.
If a light source is far away from your subject, its size is diminished in comparison to the subject. It therefore becomes harder than it would be up close. The sun (despite its massive size in comparison to any subject or scene on Earth) produces a hard light because of its great distance from Earth.
The size of a light source and its distance from your subject work together to determine the quality of light that falls on your subject.
Because your subjects are typically small when you’re shooting macro or close-up photography, you can use most lights to produce either hard or soft qualities based on their distance from your subjects. Even a battery-operated flash covers a larger surface area than most insects or small flowers. Move the flash close enough to your subject, and you can take advantage of this size relationship to create a soft light.
On the other hand, if you have a light source that’s overwhelmingly larger than your macro and close-up photography subjects, you can move it farther and farther away to increase the hardness of its quality of light.
As you move a light source closer to your subject, its intensity increases. You may need to adjust its power levels to make it work for your particular exposure settings. If you can’t lower the power settings of the light source in this situation, then try lowering your ISO or using a neutral density filter.