Required flash power?

W

wealthysoup

Suspended / Banned
Messages
147
Name
Ryan
Edit My Images
Yes
Hi everyone,

Sorry for the long post, hopefully this is easy enough to understand.

I'm thinking about getting a couple of studio lights. I'm curious as to how powerful they need to be though. I havnt decided between softboxes and umbrellas yet but if I purchase the lights I would be using them for photos of between 2 and approximately 10 people infront of a background. Presumably for an event set up the easiest way to do this would be with 2 reflective (or would shoot through be better?) umbrellas well out to each side of me and pointing down slightly on the subjects? Would anyone be able to give me the approximate light loss from each of the 3 modifiers (white umbrellas and softboxes) when used roughly 15 foot from the subjects. (unless closer would be better but probably not due to the possibility of large groups)

Would a couple of 300w heads be enough or would more powerful ones be recommended? I intend to use a couple of speedlites to light the background.

Finally, I saw a table comparing the advantages and disadvantages of different studio flashes on here awhile ago, does anybody have a link to that?

Thanks for your help
 
Power isn't all that important for most people, most of the time.
Basically you need to follow the Goldilocks formulae (not too little, not too much) because there's no point in paying more money for power that you don't need, and although there are workarounds to having too little power (the need to increase the ISO setting on your camera and reduce image quality to some extent) it's better not to have to struggle.

300Ws is probably ideal.
Speedlights on the background may be a poor choice, they will be at full power (because they don't have much power) and again you may need to increase ISO. And they recycle really slowly, which means that you'll have studio flash heads that are ready for a second shot pretty much instantly and you'll be standing there waiting for the background lights...

Light loss roughly follows the inverse square law, which says that you lose 3/4 of the light when you double the distance. It doesn't make an enormous difference whether you use a softbox or a reflective umbrella, don't use shoot through umbrellas for this, the light will go everywhere.

Basically, if you had a Lencarta UltraPro flash head (or any similar flash head) at 10' fitted with a standard reflector, 100 IS0, you'd expect to get f/16.
If you fit just about any softbox or umbrella, you'll get f/7.1 or something like it at the same distance.
If you increase the distance by 50% to 15' you'll lose half the power and will be shooting at f/4.8 (with one flash head)
 
Garry, useful info for me as well, thanks. Presumably a reflective brolly would be more directional and controllable than a shoot through brolly ? Nigel
 
Bluehawk said:
Garry, useful info for me as well, thanks. Presumably a reflective brolly would be more directional and controllable than a shoot through brolly ? Nigel
Click to expand...

Yes, typically about 60% of the light energy goes through a shoot through umbrellas, the rest bounces back, and goes everywhere.

Also, the shoot through is convex, the reflective is concave, which makes a massive difference
 
Thanks for the help Garry, I may have a few more questions within the next few weeks but thats really helped for now :)
 
You must log in or register to reply here.
Back
Top