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Not all wavelengths of light are equally visible, or equally effective at stimulating human vision, due to the spectral sensitivity of the human eye; radiation in the infrared and ultraviolet parts of the spectrum is useless for illumination. The luminous efficacy of a source is the product of how well it converts energy to electromagnetic ...
The f-number (relative aperture) determines the depth of field, and the shutter speed (exposure time) determines the amount of motion blur, as illustrated by the two images at the right (and at long exposure times, as a second-order effect, the light-sensitive medium may exhibit reciprocity failure, which is a change of light sensitivity ...
A visible tan line on a woman whose skin has been darkened by ultraviolet exposure, except where covered. Sun tanning or tanning is the process whereby skin color is darkened or tanned. It is most often a result of exposure to ultraviolet (UV) radiation from sunlight or from artificial sources, such as a tanning lamp found in indoor tanning beds.
The relation between watts and lumens is not just a simple scaling factor. We know this already, because the 60 watt incandescent bulb and the 15 watt compact fluorescent can both provide 900 lumens. The definition tells us that 1 watt of pure green 555 nm light is "worth" 683 lumens. It does not say anything about other wavelengths.
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally ...
The whole detailed discussion about lumen output of 120V vs 230V lamps is off-topic for this page defining and discussing lumen. Take it to a luminous efficacy page, if there is one. Here just give an example like a "typical" candle at about 10 lm, a 100W bulb at about 1500 lm, a streetlight at 20,000-50,000 lm.
The effective temperature of the Sun (5778 kelvins) is the temperature a black body of the same size must have to yield the same total emissive power.. The effective temperature of a star is the temperature of a black body with the same luminosity per surface area (F Bol) as the star and is defined according to the Stefan–Boltzmann law F Bol = σT eff 4.
Nearly all digital SLRs take pictures in a 3:2 ratio, as most can use lenses designed for 35 mm film. Some photo labs print photos on 4:3 ratio paper, as well as the existing 3:2. In 2005, Panasonic launched the first consumer camera with a native aspect ratio of 16:9, matching HDTV. This is similar to a 7:4 aspect ratio, which was a common ...