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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 04 Feb 2015 (Wednesday) 17:07
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mdaddyrabbit
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Feb 04, 2015 17:07 |  #1

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?


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flowrider
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Feb 04, 2015 17:09 |  #2

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.


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mdaddyrabbit
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Feb 04, 2015 17:25 as a reply to  @ flowrider's post |  #3

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


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Wilt
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Feb 04, 2015 19:31 |  #4

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


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mdaddyrabbit
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Feb 04, 2015 21:56 |  #5

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


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Feb 04, 2015 22:14 as a reply to  @ mdaddyrabbit's post |  #6

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


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Feb 05, 2015 07:33 |  #7

Wilt wrote in post #17415691 (external link)
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")


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Wilt
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Post edited over 5 years ago by Wilt. (3 edits in all)
     
Feb 05, 2015 17:04 as a reply to  @ AlFooteIII's post |  #8

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.


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Feb 05, 2015 22:31 as a reply to  @ Wilt's post |  #9

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.


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Tom ­ Reichner
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Feb 06, 2015 00:35 as a reply to  @ AlFooteIII's post |  #10

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.


"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".

  
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Dan ­ Marchant
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Feb 06, 2015 04:10 |  #11

Tom Reichner wrote in post #17417787 (external link)
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?


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Wilt
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Feb 06, 2015 15:25 as a reply to  @ Dan Marchant's post |  #12

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


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mdaddyrabbit
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Feb 06, 2015 16:32 as a reply to  @ Wilt's post |  #13

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


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Wilt
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Feb 06, 2015 16:35 as a reply to  @ mdaddyrabbit's post |  #14

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


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mdaddyrabbit
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Feb 06, 2015 16:39 as a reply to  @ Wilt's post |  #15

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


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