Mixture of two or more liquids in which one is dispersed in the other as microscopic or ultramicroscopic droplets (see colloid). Emulsions are stabilized by agents (emulsifiers) that (e.g., in the case of soap or detergent molecules) form films at the droplets' surface or (e.g., in the case of colloidal carbon, bentonite clay, proteins, or carbohydrate polymers) impart mechanical stability. Less-stable emulsions eventually separate spontaneously into two liquid layers; more-stable ones can be destroyed by inactivating the emulsifier, by freezing, or by heating. Polymerization reactions are often carried out in emulsions. Many familiar and industrial products are oil-in-water (o/w) or water-in-oil (w/o) emulsions: milk (o/w), butter (w/o), latex paints (o/w), floor and glass waxes (o/w), and many cosmetic and personal-care preparations and medications (either type).
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The term orb describes unexpected, typically circular artifacts in photographs. Sometimes the artifact leaves a trail, indicating motion.
The technical photographic term for the occurrence of orbs, especially pronounced in modern ultra-compact cameras, is backscatter, orb backscatter or near-camera reflection.
The orb artifact can result from reflection of light off solid particles (e.g., dust, pollen), liquid particles (water droplets - especially rain) or other foreign material within the camera lens.
The image artifacts usually appear as either white or semi-transparent circles, though may also occur with whole or partial color spectrums, purple fringing or other chromatic aberration. With rain droplets, an image may capture light passing through the droplet creating a small rainbow effect.
Underwater photographers notice the effect also, which occurs for the same reason as above-water photographic artifacts. Sand, small sea life or other particles close to the lens, invisible to the diver, reflect light from the flash causing the orb artifact in the image. A strobe flash, which distances the flash from the lens, eliminates the artifacts.