Replacement Flash tube for
Interfit Stellar 600 INT 526
$70.88
Replacement modeling lamp for
Stellar 600, 1000
INT 500
$10.00
Frequently Asked Questions about
lighting
Q: What's the
difference between a Watt and a Watt-second?
A: Watts are used to rate power of
continuous light and Watt-seconds are used to rate power of flash units.
The fundamental difference is time. A flash does all its work in a
fraction of a second; floodlights are on continuously. The
definitions are as follows: Watt: {n.} the
power dissipated by a current of 1 ampere flowing across a resistance of
1 ohm Watt-second: {n.} a
unit of electrical energy equal to the work done when a current of one
ampere passes through a resistance of one ohm for one second.
Q:What
is a Guide number?
A: Guide
number is a measure of the light output of a flash unit.
It is usually rated at ISO 100 film speed in feet or meters. The
formula is: GN=FxD where GN is guide number, F is the lens aperture, and
D is the distance in feet or meters. So dividing the GN by the
shooting distance will give you your f-stop. The higher the guide
number, the more light output.
Q:
What is a more useful measure of the performance of a flash,
Watt-seconds or Guide Number?
A: Guide
number is more useful because it tells how much light is being produced
by the flash, whereas Watt-seconds are merely a measure of the power
consumption of the unit.
Q:
Is there a direct relationship between Watt-seconds and Guide Number?
A:
No. Although more power generally produces more light, it is not a
linear relationship. As flashes become more powerful, it takes a
lot more power to make a little more light. Flashes also vary in
design. Some of the biggest factors that affect light output
besides power are flashtube design and reflector design. Some
flashes are also more power efficient than others.
Q:
What is color temperature?
A:
Color temperature is a measure of the color of light produced by
a lamp or flashtube, and is rated in degrees Kelvin (K). Ideally,
for photographic purposes that light should be as close to daylight
(5500K) as possible. Photoflood lamps that are rated at 3200K need
blue correction to compensate for their warm color temperature. Color
temperature is a term that is borrowed from physics. In physics we
learn that a so called "black body" will radiate light when it
is heated. The spectrum of this light, and therefore its color, depends
on the temperature of the body. You probably know this effect from
everyday life: if you heat an iron bar, say, it will eventually start to
glow dark red ("red hot"). Continue to heat it and it
turns yellow (like the filament in a light-bulb) and eventually
blue-white.
$19.95 
Metz 40 AF4 
Photoflood Lamps
