Basic question - studio flash wattage - what is the real wattage?

[zephyrprime]

So I am looking to buy this plug in studio flash that is supposed to be 72w. However, 72w is actually very dim for a flash. A watt is defined as 1 joule per second. The true wattage of even portable flashes is huge. However, they are only capable of this high wattage because the flash lasts much shorter than one second.

So when a manufacturer says that the flash is 72 watts, do they actually mean it's truly 72 watts? Because 72 watts for 1/100th of a second is only .72 joules of energy which is extremely weak.

 

[BAK]

It's unlikely many people here are in marketing meetings, or engineering meetings, at flash unit manufacturing companies.

But here are some words written by people who do go to the meetings.

https://paulcbuff.com/Efficiency-Wattseconds-and-Units-of-Measure

For a long time, Buff specified what they called Effective Watt Seconds, in an attempt to answer questions like yours.

Regardless, under any interpretation of numbers, 72 is really low if you are using a wall plug.

BAK

 

[zephyrprime]

Hey nevermind, I actually found the answer to my question after reading some stuff. Yes that link you provide is correct.

What these manufacturers mean when they say 72watts is actually 72 watt/seconds which is simply 72 joules (watt=joule/second, watt/second = joule/second*second = joule).

So the real wattage of a 72watt flash if run for 1/100 of a second is 7200watts. There would probably be limitations once the flash duration decreased but unfortunately, I do not know what these are.

I also read that manufacturers exaggerate their numbers so 72 watts would be more like 28.8 real joules D:

 

[tugwilson]

Hey nevermind, I actually found the answer to my question after reading some stuff. Yes that link you provide is correct.

What these manufacturers mean when they say 72watts is actually 72 watt/seconds which is simply 72 joules (watt=joule/second, watt/second = joule/second*second = joule).

So the real wattage of a 72watt flash if run for 1/100 of a second is 7200watts. There would probably be limitations once the flash duration decreased but unfortunately, I do not know what these are.

Not really,

A joule is a measure of energy and, in a flash that's, the energy held in the capacitor.

Most modern flashguns and battery powered strobes have a fast acting switch (google IGBT). At full power that switch allows all the power in the capacitor to pass through the flash tube to give the maximum amount of light possible as you reduce the power the power is switched of part way through the discharge. So as you reduce the power the flash duration gets shorter.

Most mains powered strobes work differently. they only hold the amount of energy in the capacitors which is sufficient to provide the light required at that power setting. At maximum power they will hold the full capacity of the capacitors at half power only half the capacity is used. Because of the nature of a capacitor's discharge curve the highest power flash of this type is the shortest and the lowest the longest (i.e. the inverse of the IGBT flash).

So the 72Ws light with produce a maximum light output of 72 Joules multiplied by the efficiency of the flash tube (the efficiency will be less than 1, you will lose some power in the form of heat).

72Ws is the power of a standard battery strobe. Elinchrom does a 100Ws mains strobe but most are 400Ws or better. I think you may be misreading the specification.

 

[Sailor Blue]

Most hot-shoe flash units come in two max power levels as denoted by their Guide Number, about GN 30 and about GN 60.

A GN 60 flash is roughly equal to a 60Ws studio strobe is used in the same umbrella or softbox.

A 72Ws strobe is a cheap product that will have very few uses. It is likely that the power isn't adjustable at all, but at the most it will only be adjustable over a 2-stop range (1/1 to 1/4 of full power).

I had some 2-stop range 100Ws strobes and they were inadequate for almost any use. As soon as I bought some 5-stop range (1/1 to 1/32) 300Ws strobes the 100Ws ones went on the shelf.

You are much, much better off buying a low cost manual power adjustment only hot-shoe flash that is designed to work with your camera instead of a 72Ws strobe.

You can get something like the Adorama Flashpoint Zoom R2 Manual Flash with Integrated R2 Radio Transceiver (TT600) for US $65. This flash can be used on-camera or controlled and triggered when off-camera by using the Adorama Flashpoint R2 PRO 2.4GHz Transmitter for Canon (XPro-C).

--
Living and loving it in Pattaya, Thailand. Canon 5DS R & 7D - See the gear list for the rest.

 

[Mon Mendoza]

The flash rating should be in watt-second. For example if a flash is rated for 200 watt-second and the flash fires for 0.1 second then for 0.1 seconds the flash output was 2000 watts.

 

[antares103]

What was probably stated in links, but was not answered in this thread, and should be noted is Watts and Watt-seconds are measurements of consumption of energy, not brightness of light. This is where "effective Watt-seconds" came in to play, much like LED and CFL lights use today.

Several things can play into this, including circuitry that is inefficient in carrying energy to the tube. But it can also be in the form of long flash durations.

For example, a flash with 100Ws and a flash duration of 1/2000s would dissipate the entire (or very close) pulse of light within the typical 1/200s shutter speed. However, a light that has a 1/100s flash duration would have half of its light blocked from the shutter being closed for half of the flash pulse (actually, it would not be half of the light, due to flash pulse curves, but it illustrates a point that a significant amount of light would be blocked). In fact, even high end OEM speedlights get truncated exposure when at full power and maximum x-sync speed.

Also, the idea that a 100Ws flash is the same as a 1s exposure with a 100W light bulb. Since Wattage is a matter of consumption, not brightness, this idea fails in that Xenon flash is more efficient than incandescent light bulbs, meaning the flash would be brighter than the 100W bulb in this scenario (assuming the whole flash pulse was captured).

 

[Ellis Vener]

It's unlikely many people here are in marketing meetings, or engineering meetings, at flash unit manufacturing companies.

But here are some words written by people who do go to the meetings.

https://paulcbuff.com/Efficiency-Wattseconds-and-Units-of-Measure

For a long time, Buff specified what they called Effective Watt Seconds, in an attempt to answer questions like yours.

Regardless, under any interpretation of numbers, 72 is really low if you are using a wall plug.

BAK

The term “Effective Watt-Seconds” was dreamed up by someone in the marketing department At Photogenic. They were trying to sell Photogenic flash equipment as being more efficient than their chief competitors for the studio portrait photography business at the time - most like either Norman Enterprises, Novatron, Balcar, or Speedotron Brownline. How they came up with the numbers they did -through calculations or measurements or if measurements the circumstances the measurements were made in (studio size, distance from flash to subject, reflector or other modifier, and measurement method was never disclosed and frankly their competitors never did the same either but at least were honest enough to clearly state actual watt-second capacity and guide numbers with different reflectors.

Into this market in the early 1980s came Paul C. Buff, an electronics wizard with a strong background in music production studios (ever heard of Frank Zappa? He got his start in the music business at Paul Buff’s studio which Zappa later bought) whose wife at the time wanted to be a photographer. Buff went to buy her some lighting equipment and was appalled at the general engineering quality of the lights he looked at and by how much was being charged for it, so he sensed a business opportunity and started making and selling better built basic flash gear and selling it directly to customers for a lower price.his big competitor was Photogenic and to compete against them he adopted Photogenic’s “Effective Watt-Seconds” language for his marketing materials and ads but he backed it up with measurements. And the company grew. He got lucky: was in the right time, in the right place, with the right product, at the right place, and he backed it with good service.

It needs to noted that in the beginning Buff was not competing against lighting products such as Speedotron Blackline, Broncolor, Dynalite, or Profoto that was matketed toadvertising or commercial photography but small “mom and pop” wedding studios.

Later when commercial photographers did start buying Paul C. Buff, Inc. lights for commercial and newspaper work (because of price point in both cases and ruggedness in the later case) the “Effective Watt-Seconds” language was a hammer used against them by those competitors, something he acknowledged in an interview I did with him around the time the Einstein was introduced.