Question about watt-seconds and light output capability

[Michael Fryd]

If you dig a little bit you can generally find the output specs listed in f/stops for a particular distance. Then use appropriate rules of thumb to get an idea of what you need. For instance bouncing off a white wall might cost 1 to 1.5 stops.

As far as needed power, companies usually list the amp draw as well, and as long as you figure in a safety factor (sorry, my reference books aren’t with me) you won’t burn the place down.

Below, for instance the chart for Buff’s plain Jane 7-inch reflector with various moonlights.

Also, if you want light that brings out shapes a little better try a triangular light arrangement—In his book “matters of light and depth” Ross Lowell recommends placing lights in the corners along one wall and then one light in the middle of the opposite wall.

The Einstein does not come with a bundled reflector. You will get different f/stops if you the recommended 8.5" High Output reflector instead of the tested 7" reflector.

If you go by f/stops, you are judging the combination of a light with a particular reflector. Unless those are the reflectors you intend to use, the tests only give you very rough approximations.



Most companies don't list peak current draw, as that would be confusing for most consumers. If a monolight lists a peak current draw of 18 amps, you might erroneously conclude that you cannot use it on a standard 15 amp circuit, or with standard 15 amp rated plugs/outlets. Normally an average current draw of some sort is listed.

 

[SmilerGrogan]

See below

 

[SmilerGrogan]

There is no conspiracy to keep secrets from you about flash power output. Every manufacturer I’ve ever checked provide guide numbers or f-stops for its equipment. Once you’ve tracked down those stats you can easily figure out how many strobes you need.

Yes, almost all of flash makers are overly optimistic about the flash output but forewarned is forearmed. Build in a stop or so of extra power and you’ll be fine (but test, test, test before you use anything on a paying gig.

Here is the chart for the 8.5” reflector you mentioned: the E640 is the Einstein



As for amperage you’re not pulling the flash power directly from the wall. You’re using house current to charge a capacitor bank inside the flash. The Alien Bees draw from what I can tell between 4 and 8 amps with a peak about 10 percent above that. That means you can plug 1 or 2 big Bees into a socket at an event space and probably be OK. You have to stay below the circuit max because you don’t know what else you’re sharing the circuit with.

If you dig a little bit you can generally find the output specs listed in f/stops for a particular distance. Then use appropriate rules of thumb to get an idea of what you need. For instance bouncing off a white wall might cost 1 to 1.5 stops.

As far as needed power, companies usually list the amp draw as well, and as long as you figure in a safety factor (sorry, my reference books aren’t with me) you won’t burn the place down.

Below, for instance the chart for Buff’s plain Jane 7-inch reflector with various moonlights.

Also, if you want light that brings out shapes a little better try a triangular light arrangement—In his book “matters of light and depth” Ross Lowell recommends placing lights in the corners along one wall and then one light in the middle of the opposite wall.

The Einstein does not come with a bundled reflector. You will get different f/stops if you the recommended 8.5" High Output reflector instead of the tested 7" reflector.
If you go by f/stops, you are judging the combination of a light with a particular reflector. Unless those are the reflectors you intend to use, the tests only give you very rough approximations.

Most companies don't list peak current draw, as that would be confusing for most consumers. If a monolight lists a peak current draw of 18 amps, you might erroneously conclude that you cannot use it on a standard 15 amp circuit, or with standard 15 amp rated plugs/outlets. Normally an average current draw of some sort is listed.

 

[SmilerGrogan]

And here is a chart from Spedotron with a nice explanation about exposure compensation in different kinds of rooms. The Ws figure refers to Spedotron strobes only, don’t try to extrapolate it to other companies.

 

[Michael Fryd]

There is no conspiracy to keep secrets from you about flash power output. Every manufacturer I’ve ever checked provide guide numbers or f-stops for its equipment. Once you’ve tracked down those stats you can easily figure out how many strobes you need.

Yes, almost all of flash makers are overly optimistic about the flash output but forewarned is forearmed. Build in a stop or so of extra power and you’ll be fine (but test, test, test before you use anything on a paying gig.

Here is the chart for the 8.5” reflector you mentioned: the E640 is the Einstein

View attachment 2528343

In other words, the Einstein gives you for enough light at 10 feet to shoot at f/22 + 1/10. The Alien Bee B1600 gives you enough light at 10 feet to shoot at f/11+9/10.



This might make you think the Einstein is more powerful, but they both produce the same amount of light. The difference is the reflector they were tested with.

If Brand X gives you f/22 with their standard reflector, and Brand Y gives you f/16 with their standard reflector, you don't know which strobe puts out more light, and you may not know whether either reflector gives you enough spread to cover your entire subject.

As for amperage you’re not pulling the flash power directly from the wall. You’re using house current to charge a capacitor bank inside the flash. The Alien Bees draw from what I can tell between 4 and 8 amps with a peak about 10 percent above that. That means you can plug 1 or 2 big Bees into a socket at an event space and probably be OK. You have to stay below the circuit max because you don’t know what else you’re sharing the circuit with.

No. When plugged into a wall outlet, the Alien Bees draw closer to 18 amps. However this peak draw is for less than a second.

....

 

[Rico Tudor]

When plugged into a wall outlet, the Alien Bees draw closer to 18 amps. However this peak draw is for less than a second.

And just for fun, here's the current draw by my Profoto D4 1200:

(1) is the VA baseline; (2) is after pack is connected to mains but still turned off. (3)-(8) are current peaks after (single head) discharges with (8) being full energy. The D4 is not only current-limited but takes less than half of a 15-amp circuit in slow recharge mode (my customary use).

--
Canon, Nikon, Contax RTS, Leica M, Sony, Profoto

 

[SmilerGrogan]

If Brand X gives you f/22 with their standard reflector, and Brand Y gives you f/16 with their standard reflector, you don't know which strobe puts out more light

This is correct, but it doesn't matter because you're not buying a $3 light bulb.

You're investing hundreds or thousands of dollars to buy the engineering expertise of the people who designed a system. Let's assume that everyone draws from the same parts catalog, more or less. The difference between systems is the level of creativity and expertise of the people who designed them.

So if you're choosing between two systems and your choices are Company A where the engineers have designed a monolight that weighs 10 lbs and delivers f/16 for $1000 and Company B where the engineers have designed a monolight that also weighs 10 lbs but gets you f/22 for $1000, then which one are you going to choose.

Bottom line: There is NO mystery to the light output from strobes and that watt-seconds is useless except in a very broad sense. And, as you point out, the reflector you use can make quite a bit of difference.

as long as you are willing to dig into the specs and add a reasonable exaggeration factor to take into account the way the optimistic way manufacturers measure their light output.

Michael Fryd, post: 63367737, member: 108784"]
SmilerGrogan wrote:

There is no conspiracy to keep secrets from you about flash power output. Every manufacturer I’ve ever checked provide guide numbers or f-stops for its equipment. Once you’ve tracked down those stats you can easily figure out how many strobes you need.

Yes, almost all of flash makers are overly optimistic about the flash output but forewarned is forearmed. Build in a stop or so of extra power and you’ll be fine (but test, test, test before you use anything on a paying gig.

Here is the chart for the 8.5” reflector you mentioned: the E640 is the Einstein

View attachment 2528343

In other words, the Einstein gives you for enough light at 10 feet to shoot at f/22 + 1/10. The Alien Bee B1600 gives you enough light at 10 feet to shoot at f/11+9/10.

This might make you think the Einstein is more powerful, but they both produce the same amount of light. The difference is the reflector they were tested with.

If Brand X gives you f/22 with their standard reflector, and Brand Y gives you f/16 with their standard reflector, you don't know which strobe puts out more light, and you may not know whether either reflector gives you enough spread to cover your entire subject.

As for amperage you’re not pulling the flash power directly from the wall. You’re using house current to charge a capacitor bank inside the flash. The Alien Bees draw from what I can tell between 4 and 8 amps with a peak about 10 percent above that. That means you can plug 1 or 2 big Bees into a socket at an event space and probably be OK. You have to stay below the circuit max because you don’t know what else you’re sharing the circuit with.

No. When plugged into a wall outlet, the Alien Bees draw closer to 18 amps. However this peak draw is for less than a second.

....

[/QUOTE]

 

[SmilerGrogan]

Unforeseen circumstances are the constant companion of the photographer. I was on a photoshoot where a breaker was tripped every 5 minutes by a very modest power pack. Was the problem a bad breaker? Flaky connection? Back-wired socket? Who knows. Always bring that LONG 12GA extension cord so you can draw power from another circuit.

When plugged into a wall outlet, the Alien Bees draw closer to 18 amps. However this peak draw is for less than a second.

And just for fun, here's the current draw by my Profoto D4 1200:

(1) is the VA baseline; (2) is after pack is connected to mains but still turned off. (3)-(8) are current peaks after (single head) discharges with (8) being full energy. The D4 is not only current-limited but takes less than half of a 15-amp circuit in slow recharge mode (my customary use).

 

[Michael Fryd]

you may not know whether either reflector gives you enough spread to cover your entire subject.

That's why the good companies tell you the beam spread of the light with the reflector, in this case even telling you to multiply the distance times .83 to get the diameter of the beam.

It's not just beam spread, but consistency across the beam. Few real world reflectors give you a perfectly consistent light with a hard edge. Invariably, the center of the beam is brighter, and trails out as your reach the edge. The "edge" normally isn't a hard edge, but the point where the light is dimmed past whatever standard the manufacturer uses.

A reflector with a bright center hot spot can easily give you a smaller rated aperture, than a reflector with same rated beam spread, but more consistent coverage.

If you are comparing the suggested f/stop, the reflector being used really does play a huge roll. Unless you are going to use that model reflector, the rating may not tell you very much about the light.

If Brand X gives you f/22 with their standard reflector, and Brand Y gives you f/16 with their standard reflector, you don't know which strobe puts out more light

This is correct, but it doesn't matter because you're not buying a $3 light bulb.

You're investing hundreds or thousands of dollars to buy the engineering expertise of the people who designed a system. Let's assume that everyone draws from the same parts catalog, more or less. The difference between systems is the level of creativity and expertise of the people who designed them.

So if you're choosing between two systems and your choices are Company A where the engineers have designed a monolight that weighs 10 lbs and delivers f/16 for $1000 and Company B where the engineers have designed a monolight that also weighs 10 lbs but gets you f/22 for $1000, then which one are you going to choose.

If the engineers really are all using the same pool of parts with similar technology, then you should expect lights with the same Watt-Second rating to put out about the same number of Lumen-Seconds. That estimate will certainly get you into the ballpark of which light puts out more lumen-seconds. Most 640Ws strobes are capable of a higher lumen-second output than most 320Ws strobes. What we really are concerned about is which puts out more light at the same power level, and that difference may be smaller than the difference due to testing methodologies or reflector design.

I have softboxes with easily changeable speedrings. If I want to know which strobe will give me the most light on my subject with my existing softbox, I look at the lumen-second output of the strobe. That's a simple and straightforward measure of light output, that's independent of the reflector.

Bottom line: There is NO mystery to the light output from strobes and that watt-seconds is useless except in a very broad sense. And, as you point out, the reflector you use can make quite a bit of difference.

...

What's the quick way of telling which puts out more light:

• f/22 + 1/10 with a rated 45° beam spread
• f/11+9/10 with a rated 80° beam spread with fairly consistent light coverage
• f/11+9/10 with a rated 80° beam spread with a hot spot in the middle of the coverage

The answer is that you don't have enough information as to the consistency of the 45° reflector, nor whether the f/stop was measured at the center, midway to the edge, or some sort of average.

 

[SmilerGrogan]

Your questions can never be answered because you've fallen into the trap of DPReview thinking. Most of the editors and all the self-appointed experts in the forums promote the view that equipment springs into being without human intervention and are used in a vacuum where real-world conditions are not allowed to intrude. Or, geographically speaking, the ultra-comfy alternate universe of hipster Seattle.

All your questions will be answered if you redirect your expectations and start from the premise that what really matters is whether humans who designed your product and the system into which it fits did a good job or a bad job and whether the tradeoffs they made are appropriate for your style of shooting.

When you buy a strobe, you're buying into a system and part of that is you're buying the expertise of the engineers at the company. All the factors you cite can be taken care of by finding a company whose products meet your demands. And that is part of why companies like Profoto and Broncolor charge so much more than Cowboy Studio or whatever. Is the difference in price worth it? Maybe it is and maybe it isn't depending on what you need from a system.

you may not know whether either reflector gives you enough spread to cover your entire subject.

That's why the good companies tell you the beam spread of the light with the reflector, in this case even telling you to multiply the distance times .83 to get the diameter of the beam.

It's not just beam spread, but consistency across the beam. Few real world reflectors give you a perfectly consistent light with a hard edge. Invariably, the center of the beam is brighter, and trails out as your reach the edge. The "edge" normally isn't a hard edge, but the point where the light is dimmed past whatever standard the manufacturer uses.

A reflector with a bright center hot spot can easily give you a smaller rated aperture, than a reflector with same rated beam spread, but more consistent coverage.

If you are comparing the suggested f/stop, the reflector being used really does play a huge roll. Unless you are going to use that model reflector, the rating may not tell you very much about the light.

If Brand X gives you f/22 with their standard reflector, and Brand Y gives you f/16 with their standard reflector, you don't know which strobe puts out more light

This is correct, but it doesn't matter because you're not buying a $3 light bulb.

You're investing hundreds or thousands of dollars to buy the engineering expertise of the people who designed a system. Let's assume that everyone draws from the same parts catalog, more or less. The difference between systems is the level of creativity and expertise of the people who designed them.

So if you're choosing between two systems and your choices are Company A where the engineers have designed a monolight that weighs 10 lbs and delivers f/16 for $1000 and Company B where the engineers have designed a monolight that also weighs 10 lbs but gets you f/22 for $1000, then which one are you going to choose.

If the engineers really are all using the same pool of parts with similar technology, then you should expect lights with the same Watt-Second rating to put out about the same number of Lumen-Seconds. That estimate will certainly get you into the ballpark of which light puts out more lumen-seconds. Most 640Ws strobes are capable of a higher lumen-second output than most 320Ws strobes. What we really are concerned about is which puts out more light at the same power level, and that difference may be smaller than the difference due to testing methodologies or reflector design.

I have softboxes with easily changeable speedrings. If I want to know which strobe will give me the most light on my subject with my existing softbox, I look at the lumen-second output of the strobe. That's a simple and straightforward measure of light output, that's independent of the reflector.

Bottom line: There is NO mystery to the light output from strobes and that watt-seconds is useless except in a very broad sense. And, as you point out, the reflector you use can make quite a bit of difference.

...

What's the quick way of telling which puts out more light:

• f/22 + 1/10 with a rated 45° beam spread
• f/11+9/10 with a rated 80° beam spread with fairly consistent light coverage
• f/11+9/10 with a rated 80° beam spread with a hot spot in the middle of the coverage

The answer is that you don't have enough information as to the consistency of the 45° reflector, nor whether the f/stop was measured at the center, midway to the edge, or some sort of average.

 

[Michael Fryd]

Your questions can never be answered because you've fallen into the trap of DPReview thinking. Most of the editors and all the self-appointed experts in the forums promote the view that equipment springs into being without human intervention and are used in a vacuum where real-world conditions are not allowed to intrude. Or, geographically speaking, the ultra-comfy alternate universe of hipster Seattle.

All your questions will be answered if you redirect your expectations and start from the premise that what really matters is whether humans who designed your product and the system into which it fits did a good job or a bad job and whether the tradeoffs they made are appropriate for your style of shooting.

When you buy a strobe, you're buying into a system and part of that is you're buying the expertise of the engineers at the company. All the factors you cite can be taken care of by finding a company whose products meet your demands. And that is part of why companies like Profoto and Broncolor charge so much more than Cowboy Studio or whatever. Is the difference in price worth it? Maybe it is and maybe it isn't depending on what you need from a system.

...

We do seem to have different styles. My usual setup has all strobes being the same model, yet each has a different mapping from power level to f/stop. This is because I use a variety of modifiers. Many times I use modifiers that are not from the same company that manufactured the strobe

I would count it as a negative if a strobe was only compatible with modifiers from the manufacturer. Westcott and many others make modifiers that are compatible with many different brands of strobe.

But it's my personal preference to have that sort of flexibility.

 

[SmilerGrogan]

Indeed. I shoot with rented strobes and own a Photoflex and a couple of Westcotts including the magnificent Master’s Brush. Freedom is a beautiful thing once you know what you’re doing.

That said, if I could afford it I would shoot with all Broncolor or Profoto, life would be easier

Your questions can never be answered because you've fallen into the trap of DPReview thinking. Most of the editors and all the self-appointed experts in the forums promote the view that equipment springs into being without human intervention and are used in a vacuum where real-world conditions are not allowed to intrude. Or, geographically speaking, the ultra-comfy alternate universe of hipster Seattle.

All your questions will be answered if you redirect your expectations and start from the premise that what really matters is whether humans who designed your product and the system into which it fits did a good job or a bad job and whether the tradeoffs they made are appropriate for your style of shooting.

When you buy a strobe, you're buying into a system and part of that is you're buying the expertise of the engineers at the company. All the factors you cite can be taken care of by finding a company whose products meet your demands. And that is part of why companies like Profoto and Broncolor charge so much more than Cowboy Studio or whatever. Is the difference in price worth it? Maybe it is and maybe it isn't depending on what you need from a system.

...

We do seem to have different styles. My usual setup has all strobes being the same model, yet each has a different mapping from power level to f/stop. This is because I use a variety of modifiers. Many times I use modifiers that are not from the same company that manufactured the strobe

I would count it as a negative if a strobe was only compatible with modifiers from the manufacturer. Westcott and many others make modifiers that are compatible with many different brands of strobe.

But it's my personal preference to have that sort of flexibility.