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Mathew Collins

Question about lighting ratio

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Hi,

A question about lighting ratio, Key+Fill : Fill,

Key is 100 FC,  Fill is 100,  then lighting ratio is 2:1

Key is 200 FC, Fill is 100 FC  then lighting ratio is 3:1

Key is 400 FC, Fill is 100 FC  then lighting ratio is 5:1

Key is 800 FC, Fill is 100 FC  then lighting ratio is 9:1

Key is 1600 FC, Fill is 100 FC  then lighting ratio is 17:1

Something wrong with my calculation?

Is it possible to arrive at 4:1, 6:1, 7:1, 8:1 ratios?

Thanks,

Mathew Collins.

 

 

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Yup, you're making it too complicated. It's just key to fill (as far as I've always understood it).

Key 100FC : Fill 100FC = 1:1 Ratio

Key 200FC : Fill 100FC = 2:1 Ratio

and so on. 

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Posted (edited)

My understanding was Contrast/ Lighting Ratio is, key + fill : fill.

Some of the books gives the ratio as , Ex: Set Lighting Technician's Handbook, Fourth Edition Film Lighting Equipment by Harry C. Box-page 112

key + fill : fill

-Mathew Collins.

Edited by Mathew Collins

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At the end of the day I wouldn't be too worried about any formulas.. a lot of those books are very outdated by todays standards / technical advancements / tastes in lighting ...  I mean you don't have too use any fill .. I almost never do.. how it looks to your eye is alot more important .. 

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8 hours ago, Mathew Collins said:

My understanding was Contrast/ Lighting Ratio is, key + fill : fill.

Some of the books gives the ratio as , Ex: Set Lighting Technician's Handbook, Fourth Edition Film Lighting Equipment by Harry C. Box-page 112

key + fill : fill

-Mathew Collins.

Interesting. I can't say that method makes an awful lot of sense to me. 

I've always understood and expressed ratios in stops. So at a 2:1 ratio, the key would be 1 stop higher than the fill. At 4:1 it would be 3 stops higher etc. etc.

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I think you can use what ever formula you like as long as you are consistent. I assume that this will be for your own use and learning only.

Just curious, what goal do you have for making these notes of lighting ratios?  I suppose they might be useful if one wants to recreate a lighting setup at a later date.

But, for matching lighting from different camera angles, I don't think it will be very useful, as from my personal experience, it's the "perceived" match that matters, and not an exact match.  For example, a very wide shot might have a bit higher lighting ratio than a close up that needs to cut from the wide shot.

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Thank you all. That clears lot of questions.

I was confused about key + fill : fill which is given in many books.

Now I could go with Key: Fill .

-Mathew Collins

 

 

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Just go with what looks best.. you don't have to follow any set manual .. or ratio.. many are very old fashioned "you should do this when you shoot this" ratio,s... very often you don't need any fill or a tiny bounce..  your better off reading up about some of the DP,s who dont follow any rules.. like Roger Deakins.. technical knowledge is of course important.. but "how to light manuals "..from donkeys years ago.. chuck them..   🙂 

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