File:Four mirrors - dielectric aluminum silver and chrome.jpg

English: Four different mirrors, each measuring about 1 inch in diameter, showing the difference in reflectivity. Clockwise from the upper left: Dielectric mirror (75--80% reflective between 500 and 600 nm), aluminum coated (85--90% reflective), chromium plated (~ 25% reflective), and enhanced silver (99.9% reflective). Three are first-surface mirrors with a flatness of λ/20. The chrome mirror is a second-surface mirror made of plate glass, cut from an automotive mirror. Note: The exposure time and aperture settings of the camera were reduced to avoid overexposure and accurately demonstrate reflectivity. For example, the mirrors are all sitting upon white paper as a reference. Although attempts were made to keep the lighting centered between the mirrors so that they only reflect the white ceiling, the dielectric mirror is on a three-degree wedge prism. Thus, a ghost reflection of the LED light-bulb is clearly visible from the uncoated second-surface, which transmits back through the mirror-coating as if it were an antireflection-coating.