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06/20/2008 12:41:34 PM · #26 |
Originally posted by Man_Called_Horse:
What does the duration have to deal with output? |
Nothing, except that back a ways someone was trying to calculate relative values based on strobe meter recommended 1/125 setting vs continuous shutter speed required, and we were pointing out that the 1/125 does not in fact represent a "shutter speed" per se for the strobe light source, as in reality its duration is slower than that. The recommended shutter speed is to allow the curtain to reveal the entire focal plane during the tiny time that the strobe is actually emitting. Faster shutter speeds than (usually) 1/125 or 1/250 yield a moving slit, with the focal plane being fully revealed at no point during the exposure, basically.
R.
Message edited by author 2008-06-20 12:41:49.
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06/20/2008 01:01:46 PM · #27 |
Solar radiation (light) at sea level with clear sky is roughly 1,000 watts per square meter, continuous, and most of it visible light.
US Gov Solar Energy Link
Working backward from the sunny 16 rule, that would be iso # = shutter speed at f16 with 1,000 w/sq m available light. This is incident light, not reflected. I'm not sharp enough to figure much more from there.
This is an interesting thread if you like numbers.
eta Here's a Wiki link with lots of charts to make the number crunching easier
EV Wiki Link
Message edited by author 2008-06-20 13:09:55.
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06/20/2008 01:03:53 PM · #28 |
Originally posted by Man_Called_Horse:
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. |
nothing to do with recycle time(although a short duration can shorten recycle time as well)
only the amount of light produced in a length of time
you have to separate yourself from shutter time & presume the shutter is open for the duration of the flash
although amount of flash output can be controlled by the amount of voltage through the tube it is easier to control by limiting the duration (this also controls the color temperature as well )
there are high quality studio strobes that do have short duration ( forget the brand) it is less common
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06/20/2008 01:20:20 PM · #29 |
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. |
please, why is the sun different from any other continuous light source?
okay it's a whole lot brigher than any other artificial continuous light, but that just goes to show how bright strobe or flash light really is.
ok i'll shut up now and just continue listening to this sofisticated discussion.
;)
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06/20/2008 01:31:47 PM · #30 |
the original question was: how many watts of continous light does it take to equal a given WS from a strobe? The sun has been brought into this and 1,000 watts/SM is the number given. Interesting. I've tried to use a 300WS studio strobe to overcome mid day sun and can't do it - set the camera for the ambient light and use the strobe to blow out the scene. Distance between my light and the subject was less than that of hte sun to the earth by a few thousand miles, but putting my light at any useable distance just left it too weak to affect the exposure.
So what? That experiment implies that 1000w of sun is more bight than 300ws of strobes. BUT any test of artifical light to strobes would certainly disagree.
How about this approach? A sutdio strobe kicks out 300ws over 1/500 of second. If left on at that output (theoretically speaking) what is that in watts...if one just times it by 500 for a full second, is that a reasonable number? Would that then be the number of watts a continous light source needs to be to be equivalent?
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06/20/2008 01:36:47 PM · #31 |
Originally posted by Prof_Fate:
the original question was: how many watts of continous light does it take to equal a given WS from a strobe? The sun has been brought into this and 1,000 watts/SM is the number given. Interesting. I've tried to use a 300WS studio strobe to overcome mid day sun and can't do it - set the camera for the ambient light and use the strobe to blow out the scene. Distance between my light and the subject was less than that of hte sun to the earth by a few thousand miles, but putting my light at any useable distance just left it too weak to affect the exposure.
So what? That experiment implies that 1000w of sun is more bight than 300ws of strobes. BUT any test of artifical light to strobes would certainly disagree.
How about this approach? A sutdio strobe kicks out 300ws over 1/500 of second. If left on at that output (theoretically speaking) what is that in watts...if one just times it by 500 for a full second, is that a reasonable number? Would that then be the number of watts a continous light source needs to be to be equivalent? |
Again, the problem is that the 300Ws rating for your strobe is the amount of electrical energy dissipated by firing the strobe, not the light output. Much of that energy is dissipated as heat with the remainder being light. (that's ignoring the relatively small losses dissipated as other forms of energy). Incandescant bulbs are the same way, a 100W bulb simply consumes 100W of electrical power, most of which is dissipated as heat. A 300W light bulb switched on for one second will not produce the same amout of light as a 300 Ws strobe.
Message edited by author 2008-06-20 13:44:45. |
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06/20/2008 01:56:29 PM · #32 |
Lux
The added variable here, in addition to aperture, shutter speed, and ISO, is the intensity of the light itself. If you fix all the others, then the intensity over time is the thing: the area under the curve (intensity x time) would have to match.
An exposure using a very intense strobe light over a fraction of a second could, in theory, be equaled by a single candle over a very very long time. (neglecting color differences and uniformity of light coverage on the subject, which would be even more variables to be controlled).
Watts probably won't get you to the answer you want--light intensity is what you are trying to compare.
Message edited by author 2008-06-20 14:05:24. |
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06/20/2008 02:20:42 PM · #33 |
Good to see everyone thinking and attacking this subject head on.
The reason I asked is an interest in getting into stop motion for extremely fast subjects without any motion blur.
I started by trying to find out if high-speed-sync and a shutter of 1/1000 would take care of the problem, the reason being as at 1/250 as fast as the flash is it may be too slow. I do not know this in reality yet, however it posed the question so I asked.
I was curious if it were possible to use a continuous light source and an extremely high shutter speed of 1/2000 4000 8000. Which in hindsight would increase my needs into the hundreds of thousands of watts and would ignite my subject before my camera caught the image.
Another question is, since above 1/250 the shutter transforms its operation into a moving slit will the time of a flashes light pulse exceed the travel time of the shutter across the frame. If yes then a strobe should work, if not well, I will have a bright band across a dark image.
So I have a few answers already, it is hard if not impossible to get better results from a continuous light than a strobe. And a professional strobe like an alien bee is better than a hotshoe flash.
I believe I just read somewhere that the duration of the pulse from a hotshoe flash can be anywhere from 1/500 to 1/30000 with an average of being between 1/2000 and 1/6000. |
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06/20/2008 02:22:28 PM · #34 |
Originally posted by togtog:
Good to see everyone thinking and attacking this subject head on.
The reason I asked is an interest in getting into stop motion for extremely fast subjects without any motion blur.
I started by trying to find out if high-speed-sync and a shutter of 1/1000 would take care of the problem, the reason being as at 1/250 as fast as the flash is it may be too slow. I do not know this in reality yet, however it posed the question so I asked.
I was curious if it were possible to use a continuous light source and an extremely high shutter speed of 1/2000 4000 8000. Which in hindsight would increase my needs into the hundreds of thousands of watts and would ignite my subject before my camera caught the image.
Another question is, since above 1/250 the shutter transforms its operation into a moving slit will the time of a flashes light pulse exceed the travel time of the shutter across the frame. If yes then a strobe should work, if not well, I will have a bright band across a dark image.
So I have a few answers already, it is hard if not impossible to get better results from a continuous light than a strobe. And a professional strobe like an alien bee is better than a hotshoe flash.
I believe I just read somewhere that the duration of the pulse from a hotshoe flash can be anywhere from 1/500 to 1/30000 with an average of being between 1/2000 and 1/6000. |
To do stop motion, typically, you shoot in a darkened room, hold the shutter open on B and fire the strobe at low power. |
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06/20/2008 02:27:09 PM · #35 |
Originally posted by Spazmo99:
To do stop motion, typically, you shoot in a darkened room, hold the shutter open on B and fire the strobe at low power. |
Nods I've done it with things like dropping objects, water etc. But I am wondering now about high pressure compressed gases and liquids, like inverted canned air and freezing all the particles.
And thanks for reminding me about the power, I forget the flash does that by flashing for a shorter duration. |
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06/20/2008 02:29:42 PM · #36 |
Originally posted by togtog:
Originally posted by Spazmo99:
To do stop motion, typically, you shoot in a darkened room, hold the shutter open on B and fire the strobe at low power. |
Nods I've done it with things like dropping objects, water etc. But I am wondering now about high pressure compressed gases and liquids, like inverted canned air and freezing all the particles.
And thanks for reminding me about the power, I forget the flash does that by flashing for a shorter duration. |
Also, High-speed sync doesn't freeze motion, in fact, it's probably worse since it pulses the strobe very fast to effectively provide continuous illumination for the whole exposure. |
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06/20/2008 02:43:36 PM · #37 |
Originally posted by Spazmo99:
Originally posted by togtog:
Originally posted by Spazmo99:
To do stop motion, typically, you shoot in a darkened room, hold the shutter open on B and fire the strobe at low power. |
Nods I've done it with things like dropping objects, water etc. But I am wondering now about high pressure compressed gases and liquids, like inverted canned air and freezing all the particles.
And thanks for reminding me about the power, I forget the flash does that by flashing for a shorter duration. |
Also, High-speed sync doesn't freeze motion, in fact, it's probably worse since it pulses the strobe very fast to effectively provide continuous illumination for the whole exposure. |
Exactly, which is what brought be to the question of a continous light source that could exceed the exposure.
However I have figured out a show stopping problem. In high speed sync the shutter is a slit moving either up or down. This means different parts of the sensor will be exposed at different times, since the subject is in high speed motion its position will differ across the exposure resulting in a slanted or distorted subject.
This means the only solution to the problem is a flash with as short of a pulse as possible, which as you reminded me lowering the power of the flash shortens the length of the pulse. My SB-800 drops down to 1/128 which is pretty dim, I wonder how long the pulse is at that point.
Message edited by author 2008-06-20 14:44:09. |
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06/20/2008 02:43:48 PM · #38 |
Originally posted by Mephisto:
please, why is the sun different from any other continuous light source?
okay it's a whole lot brigher than any other artificial continuous light, but that just goes to show how bright strobe or flash light really is.
ok i'll shut up now and just continue listening to this sofisticated discussion.
;) |
simple, if you read the OP, the author wanted to know equal wattage with flash and hot lights.
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06/20/2008 02:50:34 PM · #39 |
Originally posted by Spazmo99:
Again, the problem is that the 300Ws rating for your strobe is the amount of electrical energy dissipated by firing the strobe, not the light output. Much of that energy is dissipated as heat with the remainder being light. (that's ignoring the relatively small losses dissipated as other forms of energy). Incandescant bulbs are the same way, a 100W bulb simply consumes 100W of electrical power, most of which is dissipated as heat. A 300W light bulb switched on for one second will not produce the same amout of light as a 300 Ws strobe. |
I agree that heat is a variable, but you are going to have to show me your proof in a link or a graph because I don't think it is as much as you are certifieing.
Incandescent, and gas filled globes are two different things. Gas is more efficient than a band of tungsten.
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06/20/2008 02:52:46 PM · #40 |
Wow I found figures...
From this page.
The SB-800 at 1/2 power is about 1/1000 however at 1/1 is 1/380 not accounting for testing error.
so 1/16 should be 1/8000 and he tested it as 1/7000. So a power of 1/16 should stop most things, and 1/32 being 1/12000...
Yeah so working with a low power on the flash will probably get the results I was looking for.
Thank you everyone for helping me out on this problem, sorry it got so side tracked from the original question. |
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06/20/2008 04:08:48 PM · #41 |
Originally posted by Man_Called_Horse:
Originally posted by Spazmo99:
Again, the problem is that the 300Ws rating for your strobe is the amount of electrical energy dissipated by firing the strobe, not the light output. Much of that energy is dissipated as heat with the remainder being light. (that's ignoring the relatively small losses dissipated as other forms of energy). Incandescant bulbs are the same way, a 100W bulb simply consumes 100W of electrical power, most of which is dissipated as heat. A 300W light bulb switched on for one second will not produce the same amout of light as a 300 Ws strobe. |
I agree that heat is a variable, but you are going to have to show me your proof in a link or a graph because I don't think it is as much as you are certifieing.
Incandescent, and gas filled globes are two different things. Gas is more efficient than a band of tungsten. |
OK.
Read this Wikipedia entry here, scroll down to the section on "Luminous efficacy and efficiency"
To summarize: "Approximately 90% of the power consumed by an incandescent light bulb is emitted as heat, rather than as visible light."
From the FAQ at Advanced Strobe Products, the photometric radiation efficiency is approximately 40 lumens/Watt.
Compare that to 17.5 lumens/Watt for a standard 100W incandescent bulb per the above Wikipedia link.
Message edited by author 2008-06-20 16:09:38. |
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06/20/2008 04:25:21 PM · #42 |
But most 'hot lights' these days are not hot like halogen or incandescent but of the newer compact florescent type. Watts used for light given off compared to a incandescent bulb be 1/3 or so. Great - doesn't answer the original question though.
If you want (or need) to shoot a subject at 1/125 and F8 at ISO 100 it's an easy thing to do with a strobe - most any strobe will put out plenty of light even if not on full power. The problem posed is if you wanted to make the same exposure with constant lighting (incandescent, florescent, or halogen) how much light do you need? Watts was given as it's an easy number to get one's hands on. It's not a true measure of light output - so I used a meter reading to compare halogen to strobe.
150w halogen bulb put out 9 stops less light than a 300ws strobe on full power. Simple math gives me the number of 1350 watts of halogen (9 150w bulbs) but from experience I know that 1000w of halogen is still way too little light to give me the ISO 100, 1/125 and F8. ISO 800 1/30 and F4 maybe. that's still a 6 stop shortfall but would give us something to work with. If 1200 watts gives us 3 stops, then to get 9 we'd need 3600, plus the original 150. I don't have 4000 watts of halogen lighting to test this with though. I have no way to measure the output of a strobe other than with a light meter - even using the 1/2 setting on an SB800 is still guestimating 35 ws of strobe.
If 300ws might equal 4000w of halogen, would 35ws of strobe equate to 500w of halogen? Those power rated light sources we might be able to get and measure/compare.
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06/20/2008 04:48:14 PM · #43 |
Originally posted by Spazmo99:
OK.
To summarize: "Approximately 90% of the power consumed by an incandescent light bulb is emitted as heat, rather than as visible light."
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I never new it was that much.
Bookmarked this link.
Thanks.
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