High-quality clinical photographs are taken with flash. Flash provides relatively consistent lighting and control over shadow and reflections (specular highlight). Shadow is created using texture lighting which demonstrates the 3-dimensionality of the subject represented on a 2-dimensional medium. Reflections are inevitable when photographing moist surfaces such as the cornea. However, an off-flash allows placing the flash in a location where the reflection does not cover up the pathology.
The 3 forms of lighting technique in medical photography are 1) axial lighting, 2) texture lighting and 3) flat lighting.
Axial lighting is used for 90% of clinical photographs, depending on the type of medical practice. Axial lighting technique is performed by placing the flash on the barrel of the lens directing it toward the subject. This technique minimizes shadows and gives a better color rendition of the subject.
Texture lighting creates a 3-dimensional effect on a 2-dimensional medium by increasing the size of the shadow of the subject photographed. Placing the flash at 30 to 45 degrees to the plane of the subject creates the shadow. Experimenting with the location of the flash until the desired image is obtained is recommended.
Flat lighting is similar to axial lighting but eliminates any shadow. It is used to show accurate color and color changes. Photographing skin would be the most common application for flat lighting. Using a ring flash or multi-flash unit is one method of creating flat lighting. An alternative to a ring flash is to bounce the light off the ceiling (assuming it is white) or a white sheet to give a more diffuse, less harsh light.