What is the technique called that uses a sheet of glass at a 45-degree angle for photographing untreated fingerprints on glossy surfaces?

The technique that uses a sheet of glass set at a 45-degree angle for photographing untreated fingerprints on glossy surfaces is known as coaxial lighting. This method is particularly effective for capturing the details of fingerprints because it allows light to reflect off the glass surface, illuminating the prints without introducing additional glare that could obscure them. The 45-degree angle is critical, as it helps enhance the contrast between the smooth surface of the glossy material and the raised ridges of the fingerprint, making the prints stand out more distinctly.

The other techniques mentioned do not fit this specific application as effectively as coaxial lighting. For example, reflected lighting typically refers to a broader category of lighting techniques that may not specifically involve a 45-degree angle or the glass element that maximizes detail capture in this context. Transmitted lighting involves shining light through a transparent object, which would not be applicable to photographing fingerprints on a surface. Flat lighting generally means even lighting across an entire scene or surface and may not provide the necessary contrast and definition required for such detailed work.