Light drop off

I am shooting a Canon 60D with a Sigma 17-70mm f2.8 I am using a Photogenic 600w/s light I am trying to do a head shot and make the background dark but I cannot get it to work. I am so freak-in aggravated. Can anyone help me do this?

What modifier are you using? If it's an umbrella, it spills light everywhere. On the other hand a gridded softbox will spill much less light onto the background.

Learn or read about the inverse square law. Your subject is probably too close to the background as well.

Knew I forgot something.....24x36 softbox

With a virtual point source, the Inverse Square law applies...if your light was 2.8' from the subject, and the background was back at 5.6' from the light, it is getting -2EV less light than the subject.

But with a softbox, the Inverse Square does not apply when the softbox is away from the subject by less than 3*largest dimension of the softbox...within 108" the intensity falloff is closer to Inverse Linear.

[edit] blue bolded text added for clarity

Clarity is not great but the dark background I accomplished. I will keep refining my lighting a little at the time.

Good start! I think I see your umbrella. It might be time to calibrate your monitor's black level!

Wilt wrote in post #17415691
But with a softbox, the Inverse Square does not apply when the softbox is less than 3*largest dimension of the softbox...within 108" the intensity falloff is closer to Inverse Linear.

Wilt -- Could you clarify this? The wording seems off ("softbox less than 3* the largest dimension of the softbox")

Wording is NOT 'off'

If softbox is 24" x 36", in order for it to be 'soft' and NOT subject to Inverse Square, it needs to be 108" away from subject (3 * 36") or closer; the drop off of intensity will be Inverse Linear when close to subject, transitioning progressively to Inverse Square falloff as you move the softbox farther away.

Wow, easy there.... there were some words missing and I just wanted to make sure I understood what you were saying. "when the softbox is less than 3*largest dimension of the softbox...within 108"" did not make sense.

Now I understand that you meant when the distance of the softbox to the subject is less than 3*largest dimension of the softbox...within 108"


Thank you for the clarification.

I appreciate you writing that out the way you did. It is important that people understand that many of us have no idea how to "fill in the blanks" when we leave words out, wrongly assuming that people will somehow automatically know what we are saying. Abbreviations and sentence-structure-shortcuts often lead to misunderstandings, or to a lack of understanding. Spelling every idea out, word-for-painstaking-word, assures that such misunderstandings do not occur unnecessarily.

Tom Reichner wrote in post #17417787
I appreciate you writing that out the way you did. It is important that people understand that many of us have no idea how to "fill in the blanks" when we leave words out,

I completely agree with you, because I didn't understand what Wilt wrote either... or understand why he seemed so put out by a simple a request for a clarification. Nor for that matter do I understand why you feel the need to ride into the thread with nothing positive to contribute and be a sarcastic jerk. Having a bad day?

I was not 'put out', as you put it. I merely emphasized that I had indeed stated the way I wanted it stated, in the first message...
3 * [largest dimension of the softbox] away

Wilt, where do you display your work at? Web page?

No web page display...no point in having one, now retired.

I totally understand, I didn't know if you did this for hobby and had an area you displayed your images at.