increase power output using multiple sppedlights

[kevin_mahoney1]

<p>If I mount 2 flashes (in my case Olympus FL-50R GN 50mm (165 ft)) on a bracket, use them with a shoot through umbrella, how much would my light output increase (in f- stops), if i triggered them BOTH simultaneously at full power, 1/2 power...etc.<br>

The reason I ask is because at the current time I can`t afford Alien Bees, but I have multiple speedlights (in addition I have a FL-36R (GN 36mm (108ft)) that I hope could in some way compensate.</p>

<p>Thank you in advance for all responses<br>

Kevin</p>

[lornesunley]

<p>You would get twice the light .... twice the light = 1 f-stop</p>

[david.wagle]

<p>But note that it's not 1 stop per light.</p>

<p>Multiplying lights is all about the inverse square law. Alien Bees and similar devices are cheaper than trying to do the same thing with flashes. Because of the inverse square law. If you have (2^0) light, and you want to increase by 1 stop, you need to go to (2^1) (or 2) lights. But if you need two stops, you increase by (2^2) or 4 lights. And for three stops you need to increase by (2^3) or 8 lights.</p>

<p>A B1600 is $360. Testing by various folks has suggested the guide number for that is around 450 with an 11" parabolic reflector, compared to 190 for a 580 EX II, which you can get for $460 on Amazon. That means that a hot shoe flash on full power is about (2^-1) alien bees (or less).</p>

<p>I'm not an expert by any means, but I suspect that hot shoe flashes (particularly the name brand ones) are something of a newbie tax. Once you start pricing out the better lights, they don't seem that expensive at all. The hot shoe flashes are light weight and easy to use, but if you start having to use more than 1 to light your subject from the same angle, you're probably using the wrong tool for the job.</p>

[Matt Laur]

<p>Slick hot-shoe units like Nikon's SB-900 are expensive because they have all sorts of other stuff integrated into them (IR focusing aids, remote command/slave automation, reflector zoom automation, updatable firmware, sensors to detect color temp correction gels, and a surprising amount of power in a very small package. Tremdous units for a lot of applicaitons. But for me, out come the Bees (or Einsteins, etc) before I bother with multiple speedlighs from a single position. Unless I'm shooting under circumstances that make the AC-powered units or portable power supply for them really awkward somehow.<br /><br />As David says, the horsepower per $ from a single B1600 just blows the speedlights away. Not to mention they can tolerate continued use without overheating, you don't need a pile of batteries, etc. And ... modeling lights!</p>

[frank_skomial]

<p>Lorne Sunley's statement is perfectly correct, if 2 flashes of identical power are used.</p>

[leighb]

<p>You increase the light by one full stop<br>

IFF the flashes are identical and<br>

IFF they are both pointed directly at the subjevt (not bounced off the ceiling or some such).</p>

<p>- Leigh</p>

 

[joseph_wisniewski]

<blockquote>

<p>I'm not an expert by any means, but I suspect that hot shoe flashes (particularly the name brand ones) are something of a newbie tax</p>

</blockquote>

<p>Nope. Experienced photographers tend to have both hotshoe flashes and studio strobes. I have 5 or 6 SB-800 Nikons, for event work (only use that many with an assistant, 3 for just me) and maybe 10 White Lightning studio strobes. Whatever is required for the task at hand.</p>

[david.wagle]

<p>Joseph, I'm not saying they're not useful -- after all, they can be used to light lots of stuff, and they're easily portable, and so forth. Like I said though, if someone's using multiple hotshoe flashses to light a subject from the same angle, or in the same softbox, or a single umbrella regularly then they're missing the right tool for the job. If they just buy more hotshoe flashes, then they're paying the newbie tax. IMHO anyway. Which, I will admit, is not an expert opinion by any means.</p>

[lornesunley]

<p>Well, the OP said he had two identical flashes "2 flashes (in my case Olympus FL-50R GN 50mm (165 ft))".</p>

<p>To expand a bit, when both flashes are at full power you get twice the light of one flash - or 1 stop more light. Below that you are wasting batteries to trigger both flashes at lower power. Two flashes at 1/2 power is equal to 1 flash at full power etc etc. Of course your recycling time will be less when the flashes are triggered at lower power.</p>

<p>Now the OP also indicated that studio strobes were out of the question right now for financial reasons, so that limits what can be done with acquiring new equipment at the present.</p>

<p>The paired flashes will always put out twice the power, when used with a modifier the light transmitted through will be attenuated but reduced light from the pair of flashes at 1/X power will always be twice what one flash will realize at 1/X power. If you want to increase your light on the subject, you can also use a reflective umbrella (silver) rather than a shoot through, the reflective umbrellas usually have less light loss than a shoot through umbrella. If the two flashes are pointed in the same direction and bounced off a ceiling or wall you will still get twice the light from the two as you get from one.</p>

<p>I, for one, kind of like all the automated features that are available from a dedicated hot shoe flash for a particular camera system (like the SB-800/900 and Nikon CLS compatible cameras). The automated balance fill and automated flash settings based on the pre-flash is really handy in a dynamic environment where a studio flash setup with separate flash meter requires a longer time and more detailed work to get set up. Mind you, the studio flash setup wins hands down when you do have a more static environment, plus you can use better modifiers to obtain large diffuse lighting surfaces. </p>

<p>You could also get a Paul C Buff PLM v 2 (about $100.00) - which is a large parabolic reflective umbrella to use with your paired flashes, that would do a lot for getting more light directed to your subject with less loss.</p>

[dave_redmann]

<p>As previously hinted at, there are real gains to be made, but there's a diminishing-returns relationship. Compared to a single flash, two (identical) flashes gain you 1.0 f-stop; three flashes gain you 1.6 stops, four flashes gain you 2.0 stops, five flashes gain you 2.3 stops, six flashes gain you 2.6 stops, seven flashes gain you 2.8 stops, eight flashes gain you 3.0 stops, etc. The relationship is:<br>

extra stops of light = 3.3 x LOG(number of flashes)<br>

where LOG is the base-10 (common) logarithm.</p>

<p>However, that is not remotely to suggest that there's no value in multiple flashes. Regardless of whether you need the light output, the ability to produce more even and/or multi-directional lighting can be very useful. And for this reason, at times using some of them at less than full power may be useful. And as already stated, faster recycle time is another issue.</p>

<p>Whether it makes sense to buy hot-shoe type flashes, monolights, or a pack-and-heads system depends on many factors, the most important being where and how you're going to use them. Comparing a $360 Alien Bees monolight to a similarly-priced SB-900 or whatever is a bit unfair. If all you want is inexpensive output, a used Vivitar 285-HV or Sunpak 383 Super can be had for $25 - $50, gives you a GN of 35 m or so, and has (double check, but most do) a trigger voltage that is safe for any modern camera.</p>

<p>(And a minor point: note that Guide Numbers are generally measured in meters (m), or sometimes feet (ft), not millimeters (mm); 50 m = 164 ft.)</p>