How do 1/8...1/32 work on AlienBee's strobes ?

Hi all,

I purchased two of the AB800 and one AB1600 two years ago and I played with them for a while, then I left them and I'm not back to my favourite hobby.

Each of the strobes has a certain range of numbers that can be adjusted from the back of each strobe.

This image shows what I mean.

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You've asked us to explain the basics of exposure, I would suggest reading up on google to get the basics, or buy a book like "understanding exposure". It'd take too long to type it all out.

Basically just change the sliders until you have the power level you want. Put the 1600 on full and the 800 on full, the 1600 will be twice as bright, which is about what you want. Turn the 800 down to 1/4 power and see what happens. You'll want to be using umbrellas or soft boxes on the flashes.

A stop is a unit of light, kinda. Between 1/2 and full power is one stop. Between 1/4 and full is two stops (I think). I might have that a little mixed up, I know how it all works but explaining it can be a bit tricky.

In photography lingo, one "stop" means either double the light or half the light of the stop above or below it. The difference between f/8 and f/11 on your aperture is one stop. Likewise, the difference between 1/125 and 1/250 on your shutter (for ambient light), or the difference between ISO 200 and ISO 400.

The fractions on the lights indicate the portion of their total power. 1/2 is half of full power, or one stop less. Continuing to reduce power in one stop increments, 1/4, 1/8 , 1/16 and 1/32 are each a stop less than the preceeding fraction.

So theoretically, 1/2 power at f/11 would give you the same exposure as 1/4 power at f/8, since the larger aperture compensates for the lower flash power.

Thank you guys for explaining the used-to-be-gibberish. Curtis, you've summed it all up very well. Thank you.

One more question, talking about the power, an aperture of 2.8 means that the lens can allow almost half of the available power (that's 1/2.8 ) to get into the sensor, right ?

Regarding to the flash units, how much are their full power and how do I know which setting I should use ? Should I just use Tim's method by changing the setting until I get decent exposure ?

If yes, then how Light Meters are useful in this case ?

Say that I want to use f/8.0 in my camera, should I use 1/8 or these things are totally different fruits ?

Thank you again for your great help

No, that's no how apertures work. An aperture is the ratio of the lens width to the lens length, and basically says how much light hits the sensor. F2.8 lenses let the same amount of light hit the sensor no matter how long the lens is.

Apertures start at F1.0, but that's almost unheard of, and each stop changes the amount of light hitting the sensor by a factor of two. The stops are F1.4, f2.0, 2.8, 4.0, 5.6, 8, 11, etc (multiply by 1.4). F2.0 lets in half as much light as F1.4, and twice as much light as F2.8. Between F2.8 and F8 there's three stops difference.

"Say that I want to use f/8.0 in my camera, should I use 1/8 or these things are totally different fruits ?" This makes no sense whatsoever, I can't even understand the question.

Seriously, get the book "understanding exposure", or read up on wikipedia.

The exposure you get from a light will depend on its total power, the power level you set, the modifier you use (softbox, umbrella, etc.), and the distance from the light to the subject, among other things.

Also understand that your B1600 has twice as much power as your B800, so the B1600 at half power will give you about the same exposure as the B800 at full power.

A light meter can be used in a variety of ways, but in the basic sense, it measures the amount of light and tells you what aperture setting to use for correct exposure.

Khaled wrote in post #5586840
Hi all,

I purchased two of the AB800 and one AB1600 two years ago and I played with them for a while, then I left them and I'm not back to my favourite hobby.

Each of the strobes has a certain range of numbers that can be adjusted from the back of each strobe.

This image shows what I mean.
[]http://www.alienbees.c​om …features/backpa​nel.jpg[/]

Does anyone know how I'm meant to use these numbers according with all other strobes ?

I have the the setup shown like this:

- At 45 degrees to the right, I have the AB800 attached to the softbox.
- At 45 degrees to the left, I have the AB800 attached to translucent umbrella.
- The AB1600 is for background and hair lighting.

One more more question, I see people talking about 'stops' when talking about flash units, what are these stops or steps ?

Thanks

Any particular reason you're using the AB1600 for background and hair lighting instead of as the main shooting into a softbox (where you really need the power because the diffusion effect decreases the light intensity per unit area)? Just curious.

tim wrote in post #5587039
No, that's no how apertures work. An aperture is the ratio of the lens width to the lens length, and basically says how much light hits the sensor. F2.8 lenses let the same amount of light hit the sensor no matter how long the lens is.

Apertures start at F1.0, but that's almost unheard of, and each stop doubles the amount of light going in. The stops are F1.4, f2.0, 2.8, 4.0, 5.6, 8, 11, etc (multiply by 1.4). F2.0 lets in half as much light as F1.4, and twice as much light as F2.8. Between F2.8 and F8 there's three stops difference.

"Say that I want to use f/8.0 in my camera, should I use 1/8 or these things are totally different fruits ?" This makes no sense whatsoever, I can't even understand the question.

Seriously, get the book "understanding exposure", or read up on wikipedia.

Shouldn't that read: Apertures start at F1.0, but that's almost unheard of, and each stop cuts in half the amount of light going in.

gryphonslair99 wrote in post #5592178
Shouldn't that read: Apertures start at F1.0, but that's almost unheard of, and each stop cuts in half the amount of light going in.

Oops, yeah.

Basically: Figure out what aperture you want to shoot at. Get a light meter. Set up the lights how you want them then meter the amount of light and see what aperture it gives you. Adjust the settings on the lights until your light meter reads the aperture that you want to shoot at. Start shooting and make any adjustments you deem necessary.