How many watts?

Hi everyone.

 

I'm a newbye in studio photography so I'm looking for learn about studio

flash.

How many watts do I need to use in a main light for a full body photograph,

sinse I use most small and medium format cameras?

Thanks for any tips!

Unfortunately flash efficency varies with manufacture, so one company's watt seconds may not equal another's. Try to find something listed in guide #'s as that's a fixed measurement. But even then you'll need a flash meter (unless you're using digital where you can just do test shots and look at the results). Also it depends on how far the light is from your subject and whether you're using a soft box, umbrella or direct hard lighting. Read up on flash first at this web site (http://www.photo.net/learn/studio/primer) and others and then visit the manufacture's web sites and start learning what's available (start with White Lightning: http://www.white-lightning.com/). The main rule of thumb is: you can never have too much light, so buy as much as you can afford.

I would caveat that last statement...as long as you can dial it down to do what you want too. A 2400 w/s Speedo pack is enough light for almost any situation. Try to use it with a single light near a human subject and you will be searching for neutral density filters!! I have learned that the amount of light hitting the subject makes a tremendous difference, do not be fooled into thinking that 'just stopping down' takes care of it. It doesn't. Really.

 

So I would have to say that at 1200 w/s Profoto Acute pack could handle any lighting situation with a portrait head to toe with a single subject for small, medium and probably even large format camera. On the other hand there are lots of other manufacturers like Elinchrom that make nice mono lights (that's what I use, can't aford Profoto actutes even, let alone a 7A!!) and on the lower end Alien Bees. These are held in high regard by a lot of people on the board and that I know personally...however, I always suggest going with a more open and supported system (see what 3rd party accessories are available). That's why I decided on Elinchrom...moderate price with lots of accessories...

 

One thing, Personally I light a lot of head to toe, close up with a singley umbrella, dialed all the way down to....18 w/s.

 

Peter

500 w/s will probably be adequate.

A strobes flash capacitor has a capacity in watt seconds; NOT watt/seconds; NOT watts per second. A mistake like this is like saying fstopshutter; or that iso is an fstop; or a tripod is the aperture. Its nonsense. Its like calling miles per gallon "gallon miles". Its like saying "bowl over super" versus Superbowl<BR><BR>A watt-second is a Joule; a unit of energy. You take the DC voltage on the capacitor; square it; multiply by the caps capacitance; and divide by 2 to get watt-seconds; ie joules.<BR><BR>Watts per second is not the correct unit. Its the rate of change in power versus time; like the flashtubes rampup; like the how the power load varies when a utility turns on a cites grid and a big spike happens.<BR><BR>If you leave your 100Watt room light on 60 seconds the energy used is 6000 watt- seconds; NOT 6000 watts per second. <BR><BR>Look at your electric bill; its in kilowatt-hours; NOT Kilowatts per hour.<BR><BR>If you apply for a job; or talk around a client; improper goofy terms wont help you land a job better; it may bring up questions on what other holes one has in ones knowledge.

How the "watt-seconds" in the cap gets converted to light on your studio thing being photographed is lossy. There is heat lost in the flashbulb. Your room lights also release heat too. The reflector size; shape can be focused' or a bare bulb. A 60 watt room light has less focus than a cars 60 watt high beam headlite.

Thanks to all for your time. I'm looking for brands and found out that the Speedotron has nice prices. I have $2000 to spend on lights. Is it a good choice?

"A strobes flash capacitor has a capacity in watt seconds; NOT watt/seconds; NOT watts per second." - getting closer, but not quite...

 

Not if that has any practical implication...just to clear up a bit.

 

Capacity of a capacitor is measured in Farads, or more practical in Micro Farads or Milli Farads. Capacitor's energy is measured in WattSeconds.

Rodolfo,

 

In answer to your question, Speedotron is a very good choice.

 

By the way Frank farad, microfarad and millifarad all start with lower case letters in SI, and according to the NIST (US National Institute of Science and Technology) reference on units.

 

Best, Helen

Here I as a registered Professional Electrical engineer always capitalize Farad, its from Michael Faraday, a blokes name. The "proper" folks are always farting around changing things so their papers can be published with the proper way for their paper to be published. I draw schematics with the old school capacitor symbol, use uuF in RF, and uF in controls, draw the little loop where wires cross in a schematic, draw the circle around the transistor junctions, use the old symbol for earth and batteries. <BR><BR>

Actually a flash capacitor does have the capacity in energy in watt seconds when charged; because the charge circuit charges the cap to a specific voltage usually 500 to 600 volts.

Kelly,

 

I simply follow the SI system, and the guide to the use of units in technical writing produced by the NIST. Units don't get capitalised just because they are named after a person in those systems - watts, volts, amperes, newtons, farads, kelvins, etc etc. It's far from new, and it does follow an international convention. I would have expected PEs, CEngs, EurIngs etc to follow SI/NIST conventions in their professional documents more rigorously than laymen on photo.net, but that's just my expectation, it's no big deal, and American engineers still have to handle the inconsistent I-P unit system so they deserve a lot of slack.

 

Best, Helen