What does an “octabank at f8” really mean?

September 3, 2010 — 7 Comments

I’ve received a bunch of questions asking what I mean when I say things like:

“The key light is a silver beauty dish at f11”

“Another medium softbox at f2.8 is four feet to camera right”

“The fill is a medium strip at f5.6”

All of these f-stop numbers are the individual light levels your light meter will read at the listed shutter speed and ISO. For example, if I’ve stated that the image was shot at 1/125, ISO 100, the f-stop number (i.e. octabank at f8) is what that octabank reads on your meter, with those settings, when fired.

I don’t comment on the power level of the actual light pack because that won’t do us much good in recreating the lighting setup. Power levels are arbitrary and vary depending on too many things (pack power, distance of light from subject, light modifiers, etc.).

Hope that helps more than confuses. If someone can explain it better, please take a crack at it.

ted sabarese photo lighting diagram of octabank on guess the lighting blog


  • Yusof Hafiz


    This website rocks! and satisfies both the photographer and inner crave for technicalities..

    Hope to see more of this website in the future

    • Thanks, Yusof. I’m guessing you’ll definitely see more of this site in the future. Doh.

  • aphotoassistant

    Great site Ted… wish I’d thought of it!

    I think you’re spot on in articulating your meaning of when you write-up the lighting diagrams. I venture to say that those who are asking are newcomers to studio lighting and just need some more time digesting how it all comes together.

    Another way to think about it, if it helps, is to use under- and over-exposure numbers to describe the light source which as it relates to the camera exposure. So if an image was shot at 1/125 @ f5.6, you can then state that the octabank (metered at f8) is +1 stop, or twice as much light as the overall exposure. In other words, the octabank is over-exposed by one-stop. Depending on the shooting circumstance, this may be, or may not be, desirable.

    Love the site… Keep up the great work.


    • Tim, you’re a genius (that trait seems to be prevalent in many photo assistants). Love the idea of adding the over/under exposure values. I already understand what I was trying to say better.

      By the way, I gotta get me one of those gaffer’s tape dispensers you made.

      Thanks for the tip.

  • Levi

    I understand the concept here, but with my limited understanding of studio lighting, light falls off the further away the source is. Does ‘softbox at f8’ mean ‘softbox a f8 where the subject is standing’? Any clarificiation would be appreciated. BTW, awesome site, i’m finding it very interesting!!

  • photoleif

    thanks for this. i get most of the idea but must be feeling a little analog today. if i hold my light meter in ambient light, i can easily demonstrate your concept. i can translate this to an understanding of it in a strobed setting, the missing link for me is, to measure strobe-generated f/8 @ 1/125, ISO100, timing is key, so you’ve… got your light meter hooked up to either a PC cord, or linked in to your radio controllers of choice? thanks…

  • photoleif

    sorry: disregard my question. helps to rtfm! i was used to simpler modes in the sekonic and had been ignoring these really cool functions. thanks for the little push to go explore and learn.