Visual effects

It was soon determined that the 1931 CIE chromaticity diagram, and lumincmce function, Y, are not representative of equal visual spacing, that is, equal changes in Y do not represent equal changes in visual perception for all values of Y. Nor do equal increments of x and y represent the same visual effect for all locations on the chromaticity diagram. In other words, there is a minimum perceptual difference on both x and y (i.e.- Ax and Ay). But, the size of Ax and Ay is not the same at all parts of the chromaticity diagram. This is the same problem that Munsell encountered and is due to the fact that the human eye is... 

About 23% of regular users of hallucinogens report experiencing flashbacks. These have been classified as perceptual (visual effects), somatic (numbness), or emotional (reexperience of a disturbing emotion). Many theories about their causation remain unproved. Usually they fade with time, and no specific treatment is needed (49). 

Studies of free-ranging fossas described an orange staining of belly and breast hair, with an increased intensity in male individuals during the breeding season (Hawkins 1998). It was assumed that this visual effect is supplemented by olfactory compounds. More recently, a difference in scent-marking behaviour of male and... 

This compound (also known as Sernyl, Phencyclidine, angel dust and 1-(1-phenylcyclohexyl) piperidine) has been used as an animal tranquilizer and as a general anesthetic for human surgery. Clinical tests have shown that it has a strong tendency to produce bummers, even in people who dig other psychedelics, but under appropriate conditions some subjects like it. It produces no visual effects, a tendency to fear and anxiety, and could not easily be confused with any other psychedelics. The trip is short (about two hours) at least with low doses (about 10 mg). PCP is probably a waste of time. 

The multilayer film of the optical core produces a green reflector. The visual effects of the green reflector are not easily reproduced, yielding the easily identified security feature. Possible raw materials are polystyrene (PS), and polymethylmethacrylate (PMMA). There is a substantial difference in refractive... 

The toxins affect the central nervous system (CNS). Symptoms start within twenty minutes and may last for two to four hours, but peak hallucinogenic activity rarely lasts for more than one hour. Symptoms include anxiety and tension, visual effects such as blurring, euphoria, increased color perception with closed eyes, but also headache and fatigue. The overall sensation is usually described as pleasant. 

Although the compositions used in fountains are usually based on black powder propellant, the sparks that are responsible for the fountain effect originate from other substances within the composition. These substances are known as emitters and it is the physical and chemical properties of the emitters that determine the characteristics of the fountain. Various additives are also used to promote the visual effects or to cheapen the composition. 

Thus, in summary, the composition can be divided into propellant, emitter and additives. The propellant is invariably gunpowder, whilst the emitter might be carbon, steel, iron, aluminium, magnesium/ aluminium alloy or even titanium. Additives are often used to promote the visual effects and to cheapen the composition. 

Some fountain compositions tend to be oxidant-rich due to the presence of excess potassium nitrate or sometimes various oxalates. The reason for this is to reduce the burning rate and/or to enhance the visual effects. Certainly if gunpowder is considered to be a mixture of fuels (charcoal and sulfur) and oxidant (potassium nitrate) then the maximum rate of burning should coincide with a slightly under-oxidised system. The burning rate is therefore reduced by adding excess nitrate to the system. 

In general, excited atoms emit spectral lines, i.e. the radiation lies in very narrow wavelength ranges of width 10 to 10 nm. In practice, atomic resonance lines from species, such as strontium in a red star, contribute little to the visual effect since the emission falls in the short wavelength part of the spectrum (this line may be observed in a Bunsen burner flame at 461 nm). 

CHINESE EIRE A pyrotechnic composition based on meal powder, iron hlings and charcoal which is designed to produce visual effects including sparks. 

LANCE Small, tubular firework designed to emit a coloured flame for about 90 seconds. Used for a visual effect in set-pieces. 

MALTESE WHEEL A firework wheel which, when lit, shows the pattern of the Maltese Cross and other visual effects. 

STAR A compressed pellet of explosive composition designed to be projected as a pyrotechnic unit, with visual effects. Used in mines, shells, rockets and Roman candles. 

The fireworks industry remains perhaps the most visible example of pyrotechnics, and also remains a major user of traditional black powder. This industry provides the pyrotechnician with the opportunity to fully display his skill at producing colors and other brilliant visual effects. 

Several interesting visual effects can be achieved by careful selection of the fuel and oxidizer for a spark-producing composition. 

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