Although some of the following items are specific to ProFoto Lighting equipment, much of the information is applicable to all other brands of Professional Photographic Flash Lighting systems and photography in general.

Asymmetrical Light Distribution:
Lamp heads connected to the same flash-generator can use different amounts of energy.

Auto-bracketing:
The generator is automatically charged with different amounts of energy, giving a sequence of three exposures, of which one is "correct", one is overexposed and the third is underexposed. This function can be set to allow for a difference of 1/3, 1/2 or 2/3 f-stops.

Automatic voltage selection:
The generator can be connected to mains outlets anywhere in the world. It senses the voltage in the mains and automatically adjusts itself to their voltage.

Background light:
The lighting that illuminates the background and does not affect the lighting of the subject.

Ballast:
See "Electronic Ballast" and "Magnetic Ballast".

Black frames:
Unexposed frames on a roll of film.

Bouncer:
For thirty years now, "Bouncer" has been Profoto's for reflectors made of soft, collapsible material soft-boles. The term has now become internationally accepted as the of this TYPE of large light source.

Capacitor rotation:
Capacitor rotation is the charging principle for ProPack, which allows different capacitors to be used, when small amounts of energy are discharged. In this way, the heat is evenly distributed, and long sequences of flashes-without interruption-are made possible.

Character lighting:
A source of light that is placed close to the subject. In portrait photography, it is meant to give form and character-to the subject's face.

Compact flash-unit:
See Mono-block.

Continuous fan:
With the selector on Profoto's lamp heads, the thermostat-driven fan can be made to function non-stop.

Continuous light:
Continuous light is emitted by the Tungsten and ProDaylight lamp heads, which lamps shine continuously, unlike the flashtubes.

Contrast:
Contrast is the difference between the brightest light and the least illuminated shadow. It can be estimated in f-stops, and should not, as a rule, exceed the limits of the film's contrast capacity.

Converters:
ProCar6 and ProCar24 are examples of converters that can convert 12 volt of direct current (from a battery) into 230 volts of alternating current, which can then be used to charge a generator or provide power for lamps.

Daylight:
ProDaylight, which is Profoto's for the lamp head that uses HMI and MSR lamps, is meant to imply that this continuous source of light maintains largely the same temperature as given off by the flash, or by real daylight (around 6000 degrees Kelvin).

Digital capture:
In photographic context, all electronic (non-film) registration of pictures.

Disc reflector:
Profoto's smallest reflector, which is meant to be used together with an umbrella. Its narrow diameter makes it inefficient as a direct-light source.

Electronic Ballast:
Ballast is a necessary accessory to the ProDaylight, which is meant for HMI or MSR lamps. Among other benefits, electronic ballast provides the high voltage (around 45000 V) that is required to ignite the lamp. It also re-shapes the sine curve into a quadratic wave, giving flicker-free light, which means that the normal zero crossing will not extinguish the lamp 100 times per second (at 50 Hz). Thus, short exposures can be used in still photography or filming (without black frames turning up), and long exposures can be used for digital-scanning of pictures, without "noise" or missing parts on the scan.

Energy:
The energy-stored in the flash-generator-that will be converted into light is reckoned and expressed in Ws (watt-seconds) or Joules. Energy is dependent on the capacitance of the capacitors and the voltage to which they are charged.

Energy span:
The area within which energy can be adjusted in a generator. Each division by half of the energy, as well as each doubling of it, corresponds to plus or minus one f-stop on the camera.

Flagging the light:
To some extent, a Barn-door on the reflector or a louver in front of the soft-box can be used to round off the lighting edge. For a sharp, distinct lighting edge, a flag will have to be placed at a distance from the light source, close to the subject.

Flash Duration:
According to the international standard, the time from flash-tube igniting up to a specified point (t0,5), at which the light is no longer considered to affect the exposure.

Flicker-free light:
See "Electronic ballast".

Focusable light:
With a focusable reflector, the light can be adjusted for different types of distribution and strength.

Focusable spotlight:
The light from a focusable spotlight can be adjusted to produce a larger or smaller point of light, and sharper or less sharp light contours.

Guide number:
A recommended number for a certain combination of head and reflector, by means of which the correct camera f-stop can be estimated. The given guide-number concerns the total energy of the generator in question, and a film speed of 100 ASA. Thus, the guide-number provides the correct f-stop if the source of light is placed one meter/foot from the subject, lighting it primarily from the front. If the light-source is farther from the subject, the guide number is divided by the number of meters/feet, to arrive at the right f-stop. The following example will illustrate a situation using more complicated lighting with several flash-heads: In this case, the recommended guide-number is, say, 90. The flash-head lighting the subject is 2 meters away from it. The camera's f-stop should be 45. Another head, which is used as a background light, is not at all focused on the subject; however, it uses half of the flash-units energy, which means that the light on the subject is reduced by half. To compensate for this, the camera diaphragm is raised one f-stop to 32. Because we want a softer light, we set up an umbrella, which reduces the light again by half. We raise the diaphragm one more f-stop to 22, but we are using a film that is 200 ASA, so we have to lower the f-stop to 32. In summary: First, estimate the correct f-stop with the help of the guide-number, and add or subtract f-stops for each change you make.

Heat-absorbing filter:
This filter removes heat rays so that they will not damage slides when they are projected by a ProFocus spotlight.

HMI:
Osram's for a lamp of the "Hot Re-strike" type. Also refered to as MSR, HR.

Hot Re-strike:
Refers to HMI lighting. The lamp in use, upon being extinguished, can immediately be turned on again, even though it is still hot. The ProDaylight lamp head is meant for use with this of lamp, which is marketed under different names (for example, Osram HMI, Philips MSR, HR).

Honeycomb Grid:
These are honeycomb-like frames that admit light into the center but limit it at the periphery of the light contour, to give a toned down, concentrated point of light.

IR:
Infra-red. Using a coded infra-red signal to help send synchro impulses from the camera to the flash-unit is a commonly used METHOD .

Iris diaphragm:
The Iris diaphragm, which is an accessory to Profoto spotlights, is used to give stepless adjustment of a point of light.

Joules:
See "Energy".

Kelvin:
The temperature of a light source is given in degrees Kelvin (actually, a temperature reckoned from absolute zero). Daylight, which can vary greatly in the course of a day, is usually estimated at about 6000 degrees Kelvin, which is also the temperature given off by quartz flash-tubes. However, this will produce a far too cold, bluish light to work well with film. Profoto's lamp heads have a glass cover that lowers the temperature to one that is more compatible with film. The uncoated glass cover lowers the temperature to 5800 degrees Kelvin; the UV-coated glass cover-which is standard-lowers it to 5500 degrees (which produces a more attractive skin-tone on film); and the extra UV-coated version lowers the temperature to 5200 degrees Kelvin.

NOTE: The temperature of a flash-tube diminishes successively with the age, in terms of tube usage. The more it is used, the more quickly the change becomes noticeable.

Light distribution:
The distribution of light afforded by Profoto's reflectors has been measured from the center to the periphery. The point where the light is reduced by half (one f-stop) compared with the light in the center, defines the distribution of the light.

Lighting effect:
The different reflectors administrate the generator's energy so that the best possible lighting effect can be achieved. The success of this process depends on the character of light desired and the distribution of light, as well as on the reflector's size, form and surface structure.

Magnetic ballast:
Ballast is a required accessory to the ProDaylight lamp head, which uses HMI or MSR lamps. It provides the high voltage (some 45000 V) that required to trigger the lamp. With magnetic ballast, the lamp is extinguished 100 times a second (at 50 Hz), therefore, exposures of shorter duration than 1/100 seconds cannot be made without running the risk of black frames turning up on the film.

Magnum reflector:
The Magnum reflector is the reflector model in Profoto's product range that gives the greatest lighting effect at 50-degree light distribution .

Main light:
Basic light source for portrait photography, usually consisting of a large soft-box, placed above and behind the photographer.

Mono Block:
This term describes the ProComPact, in which the lamp/flash part is built into the generator/energy part, to constitute a single entity. This design is suitable for units that use low energy. If the energy consumption is greater, thereby rendering the unit heavier, more powerful stands will be required, and the unit will become unwieldy.

MSR, HR:
Philips' registered name for lamps of the Hot Re-strike type.

Pattern:
In this context, patterns are small sheets of thin steel plate, punched with a cut-out pattern, that are used for projection in the theater and film industries.

Pattern Holder:
Holder for the film-industries standard pattern "3".

Petrol-Electric Generator:
A petrol-driven generator that produces 120 or 230 volt of alternating current.

Photocell:
The photocell will trigger the flash-unit by a flash from another flash-unit.

Pin Spots:
Metal masks with holes of fixed sizes, that are used to project points of light with ProZoom and ProFocus spotlights.

ProCar:
See "Converters".

ProGas:
The ProGas is a transformer that can be connected between a petrol-electrical generator of 230 volts and a flash-unit, to prevent damage to either.

Quartz flash-tube:
In order to cope with the heat of repeated flashes utilizing high energy, it is necessary to make the material in a flash-tube out of quartz. Its disadvantage, however, is that it does not filter out the UV rays that can cause troublesome changes in color when certain materials-such as man-made textiles and plastics-are photographed. For that reason, the flash-tube is provided with a weak UV filter. For more information, see "Kelvin".

Recycling time:
The time between a flash going off and the generator recharging to 100%.

Scanning:
In scanning, the picture is slowly registered as lines across a surface, much the same as on a TV screen. If there is any interruption in the lighting, lines will be missing from the picture.

Shadow definition:
The sharpness or lack thereof that defines the lighted subject's shadow.

Sharpness of contour:
The sharpness of the subject as delineated against a particular background is dependent on the size of the source of light seen from the subject's perspective. In combination with a Fresnel spotlight the ProDaylight can be equipped with a non-frosted glass cover that gives a concentrated, sharp light from the HMI/MSR lamp.

Shutter blades:
Four metal frames that can be used with the ProZoom and the ProFocus spotlights to shape the light into geometrical shapes.

Snoot:
A snoot is used to gather light in the reflector into a single, small circle with diffused edges.

Special:
In this context, the combination of the ComPact and the Acute lamp head, supplemented by a Zoom reflector, a 150 W Halogen lamp and a glass cover, which makes the special "Profoto-look" in lighting.

Symmetrical light distribution:
In symmetrical light distribution, the energy from the flash-unit is distributed evenly between the lamps attached to it.

Synchro cable:
A cable through which the synchronization signal is transmitted between the camera and the flash-generator.

Synchro Interconnection cable:
A cable through which the synchronization signal is transmitted from one flash-generator to another. ( This can not be accomplished with a non-Profoto interconnection).

Thermostat/Fan cooling:
The heat in the lamp-heads is monitored by the thermostat control, which starts the cooling fan when a certain temperature is reached. When a desirable temperature is once again reached, the thermostat shuts off the fan.

Timer:
The timer indicates how long the ProDaylight has been in use.

Temperature:
To get an exact measurement of the spectrum (color temperature) that a gas-filled tube (a flash or HMI/MSR tube) gives off, a very complicated and expensive process is required. For practical uses, however, there are simple temperature meters that measure the spectrum of the light at three points, to give an approximate evaluation. Based on this, they register the temperature in degrees Kelvin.

Temperature Coatings:
Profoto supplies, as standard equipment, frosted, UV-coated glass cover (ComPact and Acute lamp head, UV-coated flashtubes and an uncoated cover), which give a color temperature of about 5500 degrees Kelvin. The glass cover can be substituted by a extra coated cover that lowers the temperature to about 5200 degrees or an uncoated cover that raised the temperature to about 5800 degrees Kelvin.

Transmitting the synchro-signal:
See "Synchro-cable" and "Synchro Interconnection-cable".

Tungsten:
The ProTungsten lamp head provides lighting by means of a Halogen lamp that yields 3200 degrees Kelvin.

Turbo charging:
The turbo-charging function allows the mains and the fuses to be overloaded for a short period, which makes very rapid flashes possible. If this is permitted to go on for too long a time-at risk of burning out the fuses-the generator automatically extends recharging time and begins charging at normal intervals. When the fuses have had time to cool off, the generator starts turbo charging again.

UV-coating:
Profoto supplies, as standard equipment, frosted, UV-coated glass cover (ComPact and Acute lamp head, UV-coated flashtubes and an uncoated cover), which give a color temperature of about 5500 degrees Kelvin. The glass cover can be substituted by a extra coated cover that lowers the color temperature to about 5200 degrees or an uncoated cover that raised the temperature to about 5800 degrees Kelvin.