In the modern headlight, this is achieved by adjusting an iris diaphragm.
For the majority of applications a light spot of 1 2' inches (37 mm) is optimal.
Many modern headlights incorporate a quartz halogen lamp which produces significantly brighter illumination with no filament shadows.
One slight disadvantage of most headlights is the absence of coaxial illumination. This problem has been overcome by some manufacturers by the incorporation of a perforated mirror for illumination; through this mirror the examiner may view the area being observed. Both the head mirror and the headlight enable the examiner to inspect the ear stereoscopically while leaving both hands free for instrumentation and manipulation.