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08/13/2004 07:13:16 PM · #1 |
| Ok, I will try and explain this so it makes sense... Just got an Alien Bee studio flash and I was taking some practice shots of my son. I took a reading with my light meter tethered to the bee via pc cord. It indicated that I should set my aperture at f8 and my shutter speed to 1/1000 sec. or maybe it was 1/640 sec. Anyway, I put a hotshoe/pc adapter into the hotshoe of my 300D, hooked up the bee and took a shot. Of course, half the frame was black because I was above my camera's flash sync speed. So, I unhooked the pc cord and used the camera's onboard flash to trip the bee. Worked great! But what if I don't want any frontal fill in my photo? I did try holding something in front of the camera's flash and that eliminated the fill but what a pain! Do I have the wrong adapter for my hotshoe? What do I do? Please advise - thanks!! |
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08/13/2004 07:19:06 PM · #2 |
| Fastest sync speed for the 300D is 1/250, set your light meter in shutter priority and measure f stop. |
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08/13/2004 07:23:57 PM · #3 |
You have to keep your shutter speed at 1/200th of a second or slower whenever you shoot flash. In most instances, the shutter speed doesn't matter if 100% of your illumination is from the flash and not from ambient lighting, because the speed of the flash tube is also faster than the shutter. So you could shoot at 1/30th of a second or 1/200th of a second (assuming camera is on a tripod so there is no camera shake) and there would be no difference in terms of flash exposure, because the flash from the strobe is much quicker than even 1/200th of a second -- it is just that 1/200th of a second is the fastest speed at which the focal-plane shutter is fully exposed. Any faster than that and the second curtain starts moving before the first curtain has reached the other side.
If you are getting a reading of 1/1000th of a second at f/8, you have way too much light and need to dial down the power of your strobe.
You definitely don't have the wrong adapter for your hotshoe. |
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08/13/2004 07:25:28 PM · #4 |
Originally posted by EddyG:
You have to keep your shutter speed at 1/200th of a second or slower whenever you shoot flash. In most instances, the shutter speed doesn't matter if 100% of your illumination is from the flash and not from ambient lighting, because the speed of the flash tube is also faster than the shutter. So you could shoot at 1/30th of a second or 1/200th of a second (assuming camera is on a tripod so there is no camera shake) and there would be no difference in terms of flash exposure, because the flash from the strobe is much quicker than even 1/200th of a second -- it is just that 1/200th of a second is the fastest speed at which the focal-plane shutter is fully exposed. Any faster than that and the second curtain starts moving before the first curtain has reached the other side.
If you are getting a reading of 1/1000th of a second at f/8, you have way too much light and need to dial down the power of your strobe.
You definitely don't have the wrong adapter for your hotshoe. |
...but what happens if the two trains are leaving Philly and San Francisco at the same time? ;o)
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08/13/2004 07:30:58 PM · #5 |
Originally posted by smokeditor:
Fastest sync speed for the 300D is 1/250, set your light meter in shutter priority and measure f stop. |
The 10D/Digital Rebel maximum sync speed is 1/200th second. =] |
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08/13/2004 07:31:10 PM · #6 |
Originally posted by laurielblack:
...but what happens if the two trains are leaving Philly and San Francisco at the same time? ;o) |
They collide and your camera goes KABOOOM! ;) :P
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08/13/2004 08:48:49 PM · #7 |
Move your light away from your subject about 10' if possible and take the reading again with an aperture choice of f/11. That should put your shutter speed requirement close to 1/200. You will need to stay at or below 1/200" with the shutter on the Rebel.
You can also dial down the power on the Alien Bee...
Message edited by author 2004-08-13 20:49:13.
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08/14/2004 11:01:16 AM · #8 |
Originally posted by doctornick:
Originally posted by laurielblack:
...but what happens if the two trains are leaving Philly and San Francisco at the same time? ;o) |
They collide and your camera goes KABOOOM! ;) :P |
LOL!
Thanks for the help!! As you can tell, I am learning as I go and perfectly clueless but having fun! By the way, Bryan Peterson's revised classic Understanding Exposure has been released. I ordered my copy yesterday :-D |
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08/14/2004 12:58:10 PM · #9 |
There are some interesting relationships between light source / distance to subject that you will want to study also. I don't know what they are off the top of my head. Moving the light source closer/farther by x number of feet increases/decreases the intensity of the light by 1 stop. I have never spent any time learning about professional lighting, but I have skimmed some materials on it....
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08/14/2004 01:52:03 PM · #10 |
| Are you talking about the inverse square law (or something like that)? |
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08/14/2004 01:54:45 PM · #11 |
Originally posted by jmsetzler:
There are some interesting relationships between light source / distance to subject that you will want to study also. I don't know what they are off the top of my head. Moving the light source closer/farther by x number of feet increases/decreases the intensity of the light by 1 stop. I have never spent any time learning about professional lighting, but I have skimmed some materials on it.... |
Scientists have calculated a theoretical relationship between brightness and distance. This predicted relationship between brightness and distance is called the inverse square law. It says that when the distance from a light doubles, its brightness should decrease by a factor of four. The equation for the brightness, written as I in the equation below, and the distance from the light, written as d, is
I = C/d2
In this equation, C is a constant that depends on how luminous the light is (in other words, what "wattage" the light bulb is). The equation for C is C=I d2.
You do not need to understand this equation in detail. The important point is that the brightness depends on distance, and that when the distance doubles, the brightness goes down by a factor of four.
(from: //cosmology.berkeley.edu/Education/public_html/Summer99/DTS/ISQ/Discussion.html ) |
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08/14/2004 02:19:53 PM · #12 |
Originally posted by photom:
You do not need to understand this equation in detail. |
Thank God! LOL
But seriously, Photom, thanks for your simplified explanation! By the way, I read your profile bio and you have my admiration. A love of learning and continuing to learn is one of life's greatest pleasures! |
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08/14/2004 04:14:11 PM · #13 |
If you think of the light to subject distance in terms of stops and remember the magic number is the square root of 2 (1.4 is close enough)It's easy to move a light and know what effect you are having on the exposure.
If you want to reduce light by one stop, simply move it 1.4x farther from the subject. Done. Just repeat as necessary to reduce more.
Example: If my main light is 10 feet from the subject and gives me f16, but I want to shoot at f11, I just need to move the light so that it is 14 feet away.
If you want more to increase the light by one stop, you have to divide the subject to light distance by 1.4 or multiply by 0.7 ( 1/1.4 ~ 0.7)
So, for the example above with the light at 10ft and f16, if I want to shoot at f22, I need to move the light to 7ft.
If you remember 1.4 and 0.7 are the magic numbers in this relationship, all you need to do is multiply.
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08/14/2004 04:16:39 PM · #14 |
Originally posted by digistoune:
[ By the way, I read your profile bio and you have my admiration. A love of learning and continuing to learn is one of life's greatest pleasures! |
Hmmmm = I thinks that's the nicest way anyone has ever called me an old fart! :)
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08/14/2004 04:17:19 PM · #15 |
Originally posted by photom:
Originally posted by digistoune:
[ By the way, I read your profile bio and you have my admiration. A love of learning and continuing to learn is one of life's greatest pleasures! |
Hmmmm = I thinks that's the nicest way anyone has ever called me an old fart! :) |
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08/14/2004 04:48:09 PM · #16 |
Originally posted by photom:
Originally posted by digistoune:
[ By the way, I read your profile bio and you have my admiration. A love of learning and continuing to learn is one of life's greatest pleasures! |
Hmmmm = I thinks that's the nicest way anyone has ever called me an old fart! :) |
LMAO!! But, of course, I didn't mean THAT at all! LOL!! |
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