Choose a camera from the evidence you need
Translate scene requirements into optics, exposure and a recording test.
Updated
Principle and limits
Describe the target, distance, scene width, motion and worst usable light. Specify what an operator must distinguish in the stored image. Megapixels alone do not answer that question: the same pixels spread across a wider scene provide less detail per metre. Form factor, mounting and illumination follow the scene requirement rather than replacing it.
Worked example
A 1920-pixel-wide recording spanning 8 m gives 240 px/m at that plane; spanning 16 m gives 120 px/m. Neither number is a guarantee of identification. A shorter exposure may be necessary for moving subjects, and a second camera may be better than forcing one wide view to provide both overview and detail.
Installation and acceptance
Test the final lens setting, mounting height and recorded stream using representative subjects at near and far boundaries. Include night, backlight and motion. Confirm power, protection, supported analytics and accessories from the exact model record. Attach accepted footage and settings to the handover so a later lens or bitrate change can be assessed.