When is a manually adjusted iris most effective?

A manually adjusted iris is most effective in constant light levels because it allows for precise control over the amount of light entering a camera or optical device. In constant lighting situations, the required exposure settings do not change, enabling the operator to set the iris to a specific aperture that optimally balances depth of field and exposure.

In variable light conditions, the changing levels can lead to improper exposure if the iris is set manually, as it may not adjust quickly enough to respond to the fluctuations in light. In low light environments, automatic adjustments might be preferable to optimize sensitivity, as manually adjusting the iris could lead to either too much or too little light entering the lens. Daylight conditions often present enough light for the camera's automatic settings to perform effectively, which may make manual adjustments less necessary. In contrast, constant light levels provide a stable foundation for the accurate deployment of manual iris settings, ensuring consistent image quality and clarity.