Flash cord adapter FA-1
•Attaches to flash's foot
•Sync cord connects to camera
•Fits flash shoe or ¼-20 threaded stand
$13.95

RPS Heavy Duty metal
umbrella adapter w/shoe
fits 1/4" thread, 3/8' thread,
and 5/8" stud lightstands
Item # RS-3104
$21.95

Flash bounce diffuser
for Canon 430EX
·Softens light for better photos
·Works at any bounce angle
·No Velcro required!
$14.95

  Photoflood Lamps

photo

500

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.