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06/20/2008 01:20:05 AM · #1 |
I've been wondering a while about this.
A flash is a quick pulse of very bright light, a continuous light is well, continuous but normally much much more dim.
I was wondering if there was a website or formula for calculating and comparing the wattage needed to equal different stops of flash power. I imagine it is many thousands of watts needed to hit the same brightness.
Thanks for any assistance.
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06/20/2008 01:41:29 AM · #2 |
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06/20/2008 01:45:26 AM · #3 |
Originally posted by togtog:
I've been wondering a while about this.
A flash is a quick pulse of very bright light, a continuous light is well, continuous but normally much much more dim.
I was wondering if there was a website or formula for calculating and comparing the wattage needed to equal different stops of flash power. I imagine it is many thousands of watts needed to hit the same brightness.
Thanks for any assistance. |
OK, I don't know of a website perse, but using both light sources in my career let me see if I can figure out what you are after.
You want an equal source of a standard hot light in wattage compared to a flash.
First look at your flash. Decide what the wattage is in your flash globe (bulb for the average layman).
If it is a 1kw globe than an equal hot light would be a....yep, a 1kw.
Dropping by a third in wattage would make it a 666 wattage, or actually a 650w.
Dropping by half would make it a 500w.
Dropping by two thirds is a 300w, or a 325w, or a 350w, going by standard sized globes.
The wattage is just math.
If you are asking about f stops, and confusing f stops with wattage, then again it is just math.
Find your stop, and divide, subtract, or add.
The Training of Lighting Designers in 1981 (T.O.L.D.) also utilizes these topics in relation to light....
A) Design Technique and Application ------------------------------------ Color, light sources, photometrics, brightness relationships, introduction to and evaluation of typical lighting applications. Drafting and visualization.
B) Human Responses to Light ---------------------------- Sight, esthetics, behavior, photobiology
C) Electrical Control and Distribution ---------------------------------------
D) Optical Control and Distribution ------------------------------------
E) Lighting Equipment Types and Application --------------------------------------------
F) Specialized Topics ---------------------- Conservation of energy, materials, safety codes and regulations, history, photographic and photoelectric reproduction technology.
I probly didn't help any.
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06/20/2008 02:37:59 AM · #4 |
Originally posted by BeeCee:
You think too much ;) |
That is the line I tried on my ex-gf. She said "I think we need to spend some time apart.". I replied "I think you think too much.". She slapped me and left, took my shotgun, my dog, and my pickup along with my heart. Women! So I went to Tennessee where heartbreak is a way of life. While there I came up with a little diddy and it goes something like this...
"My woman left me in Pittsburgh, took everything that I owned. Left me with a box of broken dreams and no rent to pay for my home. I guess I should have had a job, because when she took all that I had. I found I was really stuck in the mud and it made feel really quite bad. Listen to me, if you want to break through, the struggle is part of the plan. Don't let your tongue slip and break you apart, cause nothing can fix it again. Tell her 'Dear I don't want any other. Your face is all I can see. If I was a painter I'd paint one of you and be known in history.'. Then she'll know that you love her, and things won't be as bad, and if she still leaves you maybe she leave yer dog and you'll still have a pal. My women left me in..."
Sadly it never made it to the radio, I did get a new dog and truck though, and a shiny new D300 so I guess things worked out alright.
Originally posted by Man_Called_Horse:
I probly didn't help any. |
Not directly :) but you got my gears turning. From what I can tell my little SB-800 is about 70 watt seconds. Which means 70 watts worth of light over a one second exposure, or 140 watts over 1/2 second, 280 for 1/4...
70 1/1
140 1/2
280 1/4
560 1/8
1120 1/16
2240 1/32
4480 1/64
8960 1/128
17920 1/256
So I would need 15 thousand watts of continuous light to get the same exposure at 1/200 as I would with a flash? |
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06/20/2008 09:10:35 AM · #5 |
Originally posted by togtog:
Originally posted by Man_Called_Horse:
I probly didn't help any. |
Not directly :) but you got my gears turning. From what I can tell my little SB-800 is about 70 watt seconds. Which means 70 watts worth of light over a one second exposure, or 140 watts over 1/2 second, 280 for 1/4...
70 1/1
140 1/2
280 1/4
560 1/8
1120 1/16
2240 1/32
4480 1/64
8960 1/128
17920 1/256
So I would need 15 thousand watts of continuous light to get the same exposure at 1/200 as I would with a flash? |
You have my cogs turning as well. I find stuff like this interesting. Maybe we both can figure out what you are after together.
OK, let's assume that the 1/1 output of your flash is equal to a 70w monochromatic globe. A source of light that only has one color out put. Not the sun.
So, a 70w hot light would also be equal to a 1/1 70w flash.
The thing is if we assume that it takes a brief 1/256 to gain 17920w of intensity, it is not the same as igniting a 12kw, 18kw (both HMI) or a 20kw lamp (tungsten).
You have to consider the throw of the light, brightness, color, contrast and the spread of the source light. You have to consider the luminous flux.
Lumen, unit of luminous flux, the visible energy emitted into a given solid angle by a light source per unit time. One lumen equals the flux emitted in a unit solid angle, or steradian, by a point source with a uniform intensity of one candel. The total luminous flux of a light source divided by 4p equals the average candlepower of the source measured in all directions.
When light is considered as a source of illumination for human eyes, its intensity, or brightness, is measured in units that are based on a modernized version of the perceived brightness of a candle. These units include the rate of energy flow in light, which, for monochromatic light traveling in a single direction, is determined by the rate of flow of photons. The rate of energy flow in this case can be stated in watts, or Joules per second. Usually light contains many colors and radiates in many directions away from a source such as a lamp.
A 70w globe when reaching the 17920w of intensity in a flash is not from the globe itself, but from the mechanical function of the gear. If the 70w globe over taxed itself, or over volt, the amperage would stay the same, the globe would get brighter, and bluer on the Kelvin scale, and wear out much quicker if not stop working all together.
The flash could only over volt if it was being fed a constant source of energy, not a AA battery. A flash is basically a capacitor with a globe stuck to it.
Am I getting close to what you are looking for?
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06/20/2008 09:54:33 AM · #6 |
| The problem is that wattage doesn't necessarily equate to light output. The wattage of a light is simply how much energy it consumes. Most of that energy is dissipated as heat. The exact proportion isn't a constant across bulbs of a different wattage. |
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06/20/2008 10:04:57 AM · #7 |
You've seen the T-shirt, right ?
Dog and wife missing. Reward for Dog.
I just went and did a simple experiment...here are the results.
3x4 foot softbox on a 300ws strobe with a 150w halogen modeling light. Assuming the 300ws is a proper rating I used my Sekonic meter and got these two readings the same distance.
Strobe only: ISO 200, F16 and 1/125.
Modeling light only: ISO 200, F16 and 5 seconds.
I tried to keep it easy and change only one variable, shutter speed. So how many stops of light is the different exposures? I get 9 1/3 stops difference (please, check me on this!)
So if every stop of light is 1/2 or double the amount of light, and you start with 150watts and double it 9 times you get 76,800 watts.
Like I said - check my math - PLEASE!
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06/20/2008 10:14:34 AM · #8 |
Originally posted by Prof_Fate:
You've seen the T-shirt, right ?
Dog and wife missing. Reward for Dog.
I just went and did a simple experiment...here are the results.
3x4 foot softbox on a 300ws strobe with a 150w halogen modeling light. Assuming the 300ws is a proper rating I used my Sekonic meter and got these two readings the same distance.
Strobe only: ISO 200, F16 and 1/125.
Modeling light only: ISO 200, F16 and 5 seconds.
I tried to keep it easy and change only one variable, shutter speed. So how many stops of light is the different exposures? I get 9 1/3 stops difference (please, check me on this!)
So if every stop of light is 1/2 or double the amount of light, and you start with 150watts and double it 9 times you get 76,800 watts.
Like I said - check my math - PLEASE! |
You forgot to include the toast factor. The subjects will be too dark to shoot at some point, then beyond that wattage, they will burst into flames (you listening Leroy?) and be self illuminating. : )
Maybe thinking about the sunny 16 rule, and using the value for full sunlight would be a good starting point for calculating.
Message edited by author 2008-06-20 10:16:24.
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06/20/2008 10:18:29 AM · #9 |
Originally posted by Prof_Fate:
You've seen the T-shirt, right ?
Dog and wife missing. Reward for Dog.
I just went and did a simple experiment...here are the results.
3x4 foot softbox on a 300ws strobe with a 150w halogen modeling light. Assuming the 300ws is a proper rating I used my Sekonic meter and got these two readings the same distance.
Strobe only: ISO 200, F16 and 1/125.
Modeling light only: ISO 200, F16 and 5 seconds.
I tried to keep it easy and change only one variable, shutter speed. So how many stops of light is the different exposures? I get 9 1/3 stops difference (please, check me on this!)
So if every stop of light is 1/2 or double the amount of light, and you start with 150watts and double it 9 times you get 76,800 watts.
Like I said - check my math - PLEASE! |
Were you reading incidental? or reflective?
Message edited by author 2008-06-20 10:19:04.
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06/20/2008 10:24:45 AM · #10 |
Originally posted by MelonMusketeer:
Maybe thinking about the sunny 16 rule, and using the value for full sunlight would be a good starting point for calculating. |
The sun may be continuous and about the same color temp as flash but what's the wattage of the sun? LOL I don't think sunny 16 helps here much at all.
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06/20/2008 10:26:09 AM · #11 |
Originally posted by Man_Called_Horse:
Were you reading incidental? or reflective? |
incident.
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06/20/2008 10:29:24 AM · #12 |
Originally posted by Prof_Fate:
Originally posted by MelonMusketeer:
Maybe thinking about the sunny 16 rule, and using the value for full sunlight would be a good starting point for calculating. |
The sun may be continuous and about the same color temp as flash but what's the wattage of the sun? LOL I don't think sunny 16 helps here much at all. |
I would have to agree.
We are talking about artificial light, and the equal effects and output of flash versus standard hot lights.
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06/20/2008 10:38:25 AM · #13 |
Originally posted by Prof_Fate:
You've seen the T-shirt, right ?
Dog and wife missing. Reward for Dog.
I just went and did a simple experiment...here are the results.
3x4 foot softbox on a 300ws strobe with a 150w halogen modeling light. Assuming the 300ws is a proper rating I used my Sekonic meter and got these two readings the same distance.
Strobe only: ISO 200, F16 and 1/125.
Modeling light only: ISO 200, F16 and 5 seconds.
I tried to keep it easy and change only one variable, shutter speed. So how many stops of light is the different exposures? I get 9 1/3 stops difference (please, check me on this!)
So if every stop of light is 1/2 or double the amount of light, and you start with 150watts and double it 9 times you get 76,800 watts.
Like I said - check my math - PLEASE! |
Except the strobe exposure will be constant no matter what the shutter speed, pretty much, if you disregard the need to synch to a moving curtain. I don't recall offhand what the actual duration of the flash burst is, but it's like faster than 1/10,000 sec I think? So your calculation is WAY off. The strobe is WAY more than 9 stops brighter than the fixed light...
I think... I'm no expert at this...
R.
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06/20/2008 10:57:10 AM · #14 |
As interesting and complicated as this is, is there a point to it?
Are you actually looking to set up a continuous lighting rig that will allow you to use the same settings as with Strobes? |
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06/20/2008 10:59:54 AM · #15 |
Originally posted by pix-al:
As interesting and complicated as this is, is there a point to it?
Are you actually looking to set up a continuous lighting rig that will allow you to use the same settings as with Strobes? |
Well, I can tell y'all from personal experience that is not possible :-) The heat output is simply stunning. So is it on strobes, btw; it's just so short you don't get any buildup...
R.
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06/20/2008 11:18:49 AM · #16 |
Originally posted by Bear_Music:
Except the strobe exposure will be constant no matter what the shutter speed, pretty much, if you disregard the need to synch to a moving curtain. I don't recall offhand what the actual duration of the flash burst is, but it's like faster than 1/10,000 sec I think? So your calculation is WAY off. The strobe is WAY more than 9 stops brighter than the fixed light...
I think... I'm no expert at this...
R. |
not quite that fast ..
& note this is not T.5
from Link
"The Nikon SB-800 flash duration specifications are shown below (manual power levels, from Specifications chart, page 122). Note this is the time until the abrupt cutoff, with zero remaining output (except for full power of course).
1/1050 sec. at M1/1 (full) output
1/1100 sec. at M1/2 output
1/2700 sec. at M1/4 output
1/5900 sec. at M1/8 output
1/10900 sec. at M1/16 output
1/17800 sec. at M1/32 output
1/32300 sec. at M1/64 output
1/41600 sec. at M1/128 output
" |
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06/20/2008 11:31:35 AM · #17 |
Originally posted by ralph:
Originally posted by Bear_Music:
Except the strobe exposure will be constant no matter what the shutter speed, pretty much, if you disregard the need to synch to a moving curtain. I don't recall offhand what the actual duration of the flash burst is, but it's like faster than 1/10,000 sec I think? So your calculation is WAY off. The strobe is WAY more than 9 stops brighter than the fixed light...
I think... I'm no expert at this...
R. |
not quite that fast ..
& note this is not T.5
from Link
"The Nikon SB-800 flash duration specifications are shown below (manual power levels, from Specifications chart, page 122). Note this is the time until the abrupt cutoff, with zero remaining output (except for full power of course).
1/1050 sec. at M1/1 (full) output
1/1100 sec. at M1/2 output
1/2700 sec. at M1/4 output
1/5900 sec. at M1/8 output
1/10900 sec. at M1/16 output
1/17800 sec. at M1/32 output
1/32300 sec. at M1/64 output
1/41600 sec. at M1/128 output
" |
That's true for small speedlights, sure. My experience was with professional studio strobes, which are very powerful and very fast. In any case, we're looking (on the speedlight) at 1/1000 sec at full power, which is 3 stops faster than the "indicated" 1/125 (from the flash meter) required by shutter synch...
R.
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06/20/2008 11:42:15 AM · #18 |
Originally posted by Bear_Music:
Originally posted by pix-al:
As interesting and complicated as this is, is there a point to it?
Are you actually looking to set up a continuous lighting rig that will allow you to use the same settings as with Strobes? |
Well, I can tell y'all from personal experience that is not possible :-)
R. |
i know one light source that can: the sun!
when i took a photo of a model a few days ago, there was the setting sun from the right and my nikon sb-24 @1/2 power from the left which resulted in nearly even lighting.
now how to messure the watt equivalent output of the sun...? ;-D
interesting points you're discussing btw! |
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06/20/2008 11:50:42 AM · #19 |
Originally posted by Bear_Music:
Originally posted by ralph:
Originally posted by Bear_Music:
Except the strobe exposure will be constant no matter what the shutter speed, pretty much, if you disregard the need to synch to a moving curtain. I don't recall offhand what the actual duration of the flash burst is, but it's like faster than 1/10,000 sec I think? So your calculation is WAY off. The strobe is WAY more than 9 stops brighter than the fixed light...
I think... I'm no expert at this...
R. |
not quite that fast ..
& note this is not T.5
from Link
"The Nikon SB-800 flash duration specifications are shown below (manual power levels, from Specifications chart, page 122). Note this is the time until the abrupt cutoff, with zero remaining output (except for full power of course).
1/1050 sec. at M1/1 (full) output
1/1100 sec. at M1/2 output
1/2700 sec. at M1/4 output
1/5900 sec. at M1/8 output
1/10900 sec. at M1/16 output
1/17800 sec. at M1/32 output
1/32300 sec. at M1/64 output
1/41600 sec. at M1/128 output
" |
That's true for small speedlights, sure. My experience was with professional studio strobes, which are very powerful and very fast. In any case, we're looking (on the speedlight) at 1/1000 sec at full power, which is 3 stops faster than the "indicated" 1/125 (from the flash meter) required by shutter synch...
R. |
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. |
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06/20/2008 12:27:20 PM · #20 |
Originally posted by Mephisto:
Originally posted by Bear_Music:
Originally posted by pix-al:
As interesting and complicated as this is, is there a point to it?
Are you actually looking to set up a continuous lighting rig that will allow you to use the same settings as with Strobes? |
Well, I can tell y'all from personal experience that is not possible :-)
R. |
i know one light source that can: the sun!
when i took a photo of a model a few days ago, there was the setting sun from the right and my nikon sb-24 @1/2 power from the left which resulted in nearly even lighting.
now how to messure the watt equivalent output of the sun...? ;-D
interesting points you're discussing btw! |
If you have read the interesting points, and to keep on subject, we are talking about artificial light.
The sun is a whole different animal.
Originally posted by Spazmo99:
That's true for small speedlights, sure. My experience was with professional studio strobes, which are very powerful and very fast. In any case, we're looking (on the speedlight) at 1/1000 sec at full power, which is 3 stops faster than the "indicated" 1/125 (from the flash meter) required by shutter synch...
R. |
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. [/quote]
quote=ralph] Originally posted by Spazmo99:
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. |
my observation as well --
the three (Bowens/AB400/WL5000) i've tested all had durations of 2-5ms
(1/200 - 1/500 sec) at low or high power [/quote]
What does the duration have to deal with output?
Message edited by author 2008-06-20 12:30:14.
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06/20/2008 12:28:45 PM · #21 |
Originally posted by Spazmo99:
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. |
my observation as well --
the three (Bowens/AB400/WL5000) i've tested all had durations of 2-5ms
(1/200 - 1/500 sec) at low or high power
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06/20/2008 12:31:27 PM · #22 |
Originally posted by ralph:
Originally posted by Spazmo99:
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. |
my observation as well --
the three (Bowens/AB400/WL5000) i've tested all had durations of 2-5ms
(1/200 - 1/500 sec) at low or high power |
It also explains why camera manufacturers will often recommend a slower sync speed when the camera is used with studio lights. |
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06/20/2008 12:35:05 PM · #23 |
Originally posted by Man_Called_Horse:
Originally posted by Mephisto:
Originally posted by Bear_Music:
Originally posted by pix-al:
As interesting and complicated as this is, is there a point to it?
Are you actually looking to set up a continuous lighting rig that will allow you to use the same settings as with Strobes? |
Well, I can tell y'all from personal experience that is not possible :-)
R. |
i know one light source that can: the sun!
when i took a photo of a model a few days ago, there was the setting sun from the right and my nikon sb-24 @1/2 power from the left which resulted in nearly even lighting.
now how to messure the watt equivalent output of the sun...? ;-D
interesting points you're discussing btw! |
If you have read the interesting points, and to keep on subject, we are talking about artificial light.
The sun is a whole different animal.
Originally posted by Spazmo99:
That's true for small speedlights, sure. My experience was with professional studio strobes, which are very powerful and very fast. In any case, we're looking (on the speedlight) at 1/1000 sec at full power, which is 3 stops faster than the "indicated" 1/125 (from the flash meter) required by shutter synch...
R. |
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. |
quote=ralph] Originally posted by Spazmo99:
I think that if you look at the data, you'll find that on camera strobes typically have much shorter durations than studio strobes. |
my observation as well --
the three (Bowens/AB400/WL5000) i've tested all had durations of 2-5ms
(1/200 - 1/500 sec) at low or high power [/quote]
What does the duration have to deal with output? [/quote]
again.
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06/20/2008 12:38:06 PM · #24 |
Originally posted by Man_Called_Horse:
What does the duration have to deal with output?
again. |
if i understand your question ..
you get more light the longer the tube is lit ..
so if you choke it off - you get less light ..
Message edited by author 2008-06-20 12:38:23. |
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06/20/2008 12:41:12 PM · #25 |
Originally posted by ralph:
Originally posted by Man_Called_Horse:
What does the duration have to deal with output?
again. |
if i understand your question ..
you get more light the longer the tube is lit ..
so if you choke it off - you get less light .. |
so you are talking about illumination periods, and not recycle periods.
just wanted to make sure I understood your thoughts.
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