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Flash Vs. Strobes Power

Discussion in 'Lighting Forum' started by shanguli, Jun 12, 2015.

  1. shanguli

    shanguli Mu-43 Regular

    Sep 16, 2014
    How do you compare the power of Flashes vs. Srobes.
    I know strobs have more power (can't quantify know how much more power though), but I'm trying to understand who much more, since I'm looking into the possibility of using flashes (in lieu of strobes) by mounting them onto octa, strip softboxes, for on location headshot photography.

    For instance, I was looking at Alienbees.
    Take for instance the "AlienBees™ B800 Flash Unit" which has "6 f-stop power variability (10 Ws to 320 Ws)".

    My ( such as YN 560 IV) Flashes have from "1/1" all they way to "1/128" power option, but how does that translate to watts (as is indicated on the strobes, like the AlienBees B800, which has upto 320 Ws).
    Thank you for your great insights!
  2. oldracer

    oldracer Mu-43 Hall of Famer Subscribing Member

    Oct 1, 2010
    Well, start with the fact that "flash" and "strobe" are names for the same thing. In Olden Times, "flash" might refer to electrically-fired flash bulbs. Currently, "flash" could refer to LED flashes but as a practical matter a flash is a strobe. ("Strobe" probably from "stroboscope." Google "Harold Edgerton" for some interesting reading.)

    Camera-mounted strobes are sometimes called "speedlites." but that is probably a Canon trademark. You can also have a built-in flash/strobe in your camera. I think your question is really about comparing speedltes with studio type strobes. The short answer is that, as you have guessed, the power is measured in watt-seconds. A strobe that consumed one watt of power for one second isn't theoretically possible but that would be a 1 watt-second strobe. Strobe durations are much shorter than one second though, so for example, a 100 watt-second strobe might consume 50,000 watts for 2/1000 of a second, or 100,000 watts for 1/1000 of a second. The conversion of power to illumination is similar because most photographers' strobes use similar technlogy, but strictly speaking the watt-second rating is not an illumination rating.

    So to compare a speedlite to a studio strobe you need to know the watt-second ratings. Another way might be to compare "guide number" ratings, which are commonly part of speedlite specs, but are rare or nonexistent for studio strobes. There is probably a way to estimate watt-second ratings from guide numbers but I do not know it. Google may be your friend for this.

    It is not all about "power" though. A big advantage of studio strobes is cycle time. A studio strobe might recycle and be ready to be fired again in under one second where a speedlite might take ten. Ten seconds is an eternity in a studio shoot. Also, studio strobes use mains power, so you never run out of batteries.

    There is another flavor of "strobe" which is sort of a hybrid. These are smaller versions of studio strobes, usually with separate battery packs, that are larger and more powerful than typical speedlites and usually faster cycling. This type of strobe is used for things like weddings. I have a couple of Metz 60CT-4s that are this type. They actually work pretty well used with umbrellas but I am at the mercy of the battery life.

    Just to make things more confusing, there are also two flavors of studio strobes. "Monolights" are self-contained, including both the flash stuff and the power supply. They are bigger and heavier, but often more convenient than conventional studio strobes, where the flash stuff is mounted on the light stand and is connected to the power supply with a special cable.
    • Like Like x 1
  3. shanguli

    shanguli Mu-43 Regular

    Sep 16, 2014
    Thanks very much,
    as with monolights, what else is good out there, besides the pricy profoto b1 and d1?
  4. pellicle

    pellicle Mu-43 Hall of Famer Subscribing Member

    Feb 10, 2010
    Killarney, OzTrailEYa
    For what its worth I recently bought a bunch of (claimed to be) 5000mAH NiMH C cells off ebay (to repack a ryobi drill) and they are pretty awesome. My CT-32 cycles quite fast off modern NiMH batteries, so you may want to givethata go :) 
  5. SpecFoto

    SpecFoto Mu-43 Top Veteran Subscribing Member

    Aug 28, 2012
    So Cal
    Regarding the power question, it really depends upon what type of location shoot you are looking at. Want to shoot a model at the beach in full sun? 320ws (watt seconds) is the minimum I would consider, and even then you need to have a very efficient light modifier such as a highly reflective umbrella or silver beauty dish set pretty close to the subject. I had a couple of AB 800 and 400 in the past, the 800 at 320ws was OK for this. The 400's I mostly used for background lighting. FYI the typical speedlight flash is about 50 to 65 ws, so for these to work, you would need to gang up 4 or so in a special bracket made for this purpose. Or are you going to be at inside events or shaded areas? Assuming your not trying to light the entire area, you could get by with less power and a AB400 at about 160ws would suffice. Regarding quantity of lights for head shots, 2 is good, 3 is better and 4 is best. It all just depends on how you set up your set.

    About 16 months ago I replaced my Alien Bees with Godox manufactured bare bulb Witstro flashes (Many brands such as Cheetah light, Flashpoint Streaklight by Adorama, Neewer by Amazon and a few other on EBay. All are pretty much the same, but Cheetah and Streaklight are US based and will provide warranty service, so I would stick with them.) These lights are battery powered strobes and the battery is separate from the light. The batteries are lightweight lithium and last ALL day and the recycle time is excellent. Plus the battery pack has 2 light ports, so you can buy a $13 Y cable to effectly halve the recycle time of the lights and provide twice as many shots. So much easier to carry around than Alien Bees or almost any others stobe light. The AD360 model is the same WS as a AB 800 at 320 WS, and the AD180 model is the same as a AB 400 at 160WS. Plus they make a really great speedlight model called the V850, about the same size as a Nikon SB900. All of them can mount in a standard hotshoe or work with a variety of adapters. I have 2 of each for 6 total and about a dozen different light modifiers. My shooting usually involves beach or hi-desert areas in full sun and I just love these lights.

    Assuming you use a Pany or Oly body, you are going to be using manually triggered flash with full manual camera settings. No iTTL as of yet (at least reliable) for M4/3. Here, the Godox triggers are the best, so simple to use, as you don't have to dive into menus to change the power. A simple + / - button is all that is needed and you can set a beeper for signal confirmation for remote flash. And unlike a lot of other Chinese triggers, these are extremely reliable.

    Want to see a master wedding photog at work using these lights, check out this video:

    Last edited: Jun 14, 2015
    • Like Like x 1
  6. oldracer

    oldracer Mu-43 Hall of Famer Subscribing Member

    Oct 1, 2010
    I am not an expert on models. I have Photogenic 1250DRs bought at a good price on eBay. As an electrical engineer I can tell you that power costs money and reliability costs money. There are lots of ways to cheap out on high-power electronics ranging from using marginal components (especially capacitors) to providing inadequate cooling. For this reason I would avoid cheap, new strobes. Some of the older studio strobes also have high-voltage triggers that will ruin a digital camera (http://www.botzilla.com/photo/strobeVolts.html), so that is another caution. What I bought were used modern units from a high quality manufacturer and that is what I would recommend. Ideally, find a kit with a soft box or two, umbrellas, grids, snoots, stands, reflectors, etc. included. That stuff is expensive when bought separately, a fact not usually reflected in a used kit's price. For the same reason, try to buy a common brand so that accessories are easier to find on the used market. Buying just a bare monolight or three is like buying something that is hungry and eats money.
  7. cueball

    cueball Mu-43 Regular

    Aug 5, 2013
    I picked up a couple Adorama Flashpoint Streaklights (360 WS) a few months ago and can't recommend them enough if you want portability. So far they have worked well with both my Canon and Olympus kits.
  8. Bif

    Bif Mu-43 Top Veteran

    May 28, 2012
    San Angelo TX
    Bruce Foreman
    Shan: The "Alien Bees" are the economy line of Paul Buff's "White Lightning" line and for the money are an excellent buy. mine came with a 7" reflector which is not that usable except for directing the beam into an Umbrella. I have a pair of B800's I got mainly for location work (proms, formal events where I photographed couples and very small groupd) and while the 7" reflector is way to "raw" to turn on people, umbrellas are the cheapest way to tame them.

    My favorite was 52" white umbrellas, what I have now is a pair of leftover 52" silver. A bit more "specular" but they work well for people where you need a broad soft beam.

    If I were buying now I would get a pair of B800's, one or a pair of B400's, a "beauty dish" reflector (a reasonably priced $79.95 and I would get the white version for softer light). Maybe one of their softboxes and the standard reflectors with 80deg and 45deg beam spread are very inexpensive.

    If you have a flashmeter use that to determine your starting point for exposure. Otherwise do test exposures with a subject and evaluate the results first on the back of the camera and then on a computer. Put a string on the light stands and when you determine the correct light to subject working distance at a particular f stop, tie a knot in the string at that point.
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