FRONT LIGHTING

Front lit scenes, where the camera is on the same side of the scene as the light source or ambient light, usually is low in contrast. In this situation extreme care in setting up uniform lighting on the scene is necessary and the optimum trip light level needs to be used. Front lighting requires a multiple diffused light source such that the contrast in the scene is increased. If defects or points of interest are to be emphasized, side lighting such that the defects or points of interest cast a shadow, or increase in spectral energy (reflection) will usually point out the defects.

To set up a front lit scene, normally one or more flood lamps (outdoor flood lamps purchased from a local hardware store are adequate) are arranged around the scene far enough away so that there are no shadows. Then the f-stop, focus and lamps are adjusted for maximum contrast and focus. Adjust the focus where the smallest part of the scene has the most detail. The depth of focus (the distance the scene can move in relation to the camera and still be in focus) is increased at higher f-stops. Increase the amount of light and/or the integration time to optimize the result.

A trade-off of lighting, integration time, f-stop and scene- to-camera positioning (also lens selection) is necessary to optimize the result. Due to light falling off (at a slope of cos*cos*cos*cos) from the center of the lens going to the edges of the lens, the periphery of a scene takes more light for a uniform trip light threshold to capture the scene.