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Anonymous asked:
Hey Zack, A follow up on the ratio post please. I'm missing something. You said "You can only know ratios by using a light meter.". I don't follow. I don't get why you need to meter it to know the ratio? Before you say that you talk about how so many stops equate to a certain ratio, e.g. 3 stops difference equals a ratio of 1:8. Can't you just say my key is full 1/1 power and the fill is on 1/8th, that's 3 stops, they are both the same distance away, so that's 8:1? Why do u need a meter to tell?

This is a follow up to this question from today.

If your main and your fill are exactly the same distance from your subject and you are using the exact same modifier on each light, then yes, you can simply dial your ratios in via flash power and be very close. You are correct in your thinking.

The thing is, at least the way many photographers shoot, the main and fill would rarely, if ever, be the same exact distance and be utilizing the same exact modifier. 

For me, I choose whatever modifier I need/want/desire for the main and then I “typically” use a big umbrella or a large Octa or softbox for my fill. That fill, a lot of times, is flying over my head behind my shooting position. The main is somewhere up close to the subject. In this case it isn’t so easy to just dial a ratio in via flash power because distance changes exposure (inverse square law) as well as the type and size of modifier you are using. 

If I have my main in a small softbox that is three feet from my subject and my fill is in a seven foot octabank that is positioned fifteen feet from my subject then what power settings give you what ratio at that point? I might have my main set to 1/8th power and my fill set to a HIGHER power like 1/2 or something and yet, my fill, is actually 1 stop less than my main because of distance, the size of the fill, etc.

I can not remember the last time my main and fill were the same distance from the subject and using the same modifier on each light.

Hope that clarifies it.

Cheers,
Zack 

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  1. zarias posted this