# Lighting Ratio for Studio Photography

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#### dannynys

##### New Member
Hi,
I want to clarify this lighting ratio thing I keep asking myself. I have trouble understanding it. If I have a 2 studio lights setup, and I want the lighting ratio to be 2:1. I metered the main light to be F16, what should the fill light be at? A point to note is I have overexposed my film by 1 stop also. Hence, my camera is set at 1/60 at F11.

:dunno:

#### aesthetic

##### New Member
hmmm...

Light ratio is simply the ratio of light and dark or light and shadow from those of the main light, to those from fill light. If the ratio is 1:1, this means that the main and fill lights shine on the subject with equal strength. If the ratio is 1:4 the main light is 4 times brighter than the fill light(2 stops).

if 2:1, does that it means your trying to do a "blow off highlights" thingy?

your fill shd be 1 stop darker that is f11. you shd shoot at f16 not f11

#### dannynys

##### New Member
if 2:1, does that it means your trying to do a "blow off highlights" thingy?
Nope, I am not doing that. I am trying to do the lighting ratio where the main light is at "2" and the secondary light is at "1". So if my main light reads F16 on the meter, what should the secondary light reads to achieve 2:1 lighting ratio? Should it read F11 or F8 ? According to my friend, F11 would be only a lighting ratio of close to 1:1 , is that true?

#### aesthetic

##### New Member
Originally posted by dannynys
Nope, I am not doing that. I am trying to do the lighting ratio where the main light is at "2" and the secondary light is at "1".
i think you are after 1:2 ratio. not 2:1

this is how they read light ratios

1:2 (light : shadow or main : fill). this means your main light is 2 times stronger than your fill (which is 1 stop difference). if 1:4 that means your main is 4 times stronger than your fill (which is 2 stop difference). being your fill is the secondary light.

to answer your question. 1:2 is 1 stop difference between main and fill light. which in your case is f11

tell you what, if you are still not certain... bracket, experiment and see for yourself.

#### dannynys

##### New Member

Yes, I did try out a few lighting ratios. I think getting the basics right is important for me to understand what I am doing. Well, basically there is no much different in saying 2:1 or 1:2. As the mathematics does explain itself, just saying the strength of the lighting of the main light and the fill as you have mentioned. I mean I do encounter some people do refer it this way. Anyhow, enough of this (not getting the main point here!) , I have read on the web that the different in stops can be obtained by dividing the ratio by half. This means that the fill light in this case is to be set at 2/2= 1 stop different. The subsequent different in lighting of 1:5 , the fill light is set at -2.5 stops with reference to the main light. I hope this piece of information can be verified by anyone who is experienced in studio lights?

:dent:

#### aesthetic

##### New Member
Originally posted by dannynys

I have read on the web that the different in stops can be obtained by dividing the ratio by half. This means that the fill light in this case is to be set at 2/2= 1 stop different. The subsequent different in lighting of 1:5 , the fill light is set at -2.5 stops with reference to the main light. I hope this piece of information can be verified by anyone who is experienced in studio lights?
no worries

<maths lesson>
not actually dividing them by halves but rooting the power of 2 with n. (where n is the number of stops) for example 1:8 give you 3 stops difference which is 2³. 1:16 gives you 4 stop difference which is 2-to-the-power-of-4 and so on. so 2.5 stop difference give you a ratio of 1:5.6.
</maths lesson>

regards
happy shooting

#### dannynys

##### New Member

Well, I think I am confused already. I mean having square roots may be the correct calculations, but I guess I am no mathematician! A rough guide of the will do just fine, probably you can tell me what's the stop different I should set the lights if the ratio is 1:2 , 1:3 , 1:4 , 1:5 , 1:6 and the main light is now at F16?

Thanks, :rbounce:

#### reignman77

##### New Member
Originally posted by dannynys

Well, I think I am confused already. I mean having square roots may be the correct calculations, but I guess I am no mathematician! A rough guide of the will do just fine, probably you can tell me what's the stop different I should set the lights if the ratio is 1:2 , 1:3 , 1:4 , 1:5 , 1:6 and the main light is now at F16?

Thanks, :rbounce:
my understanding from what u are saying, means: 1:2 is F16 : F11, 1:3 is F16: F8.... as for 2:1, it should be F16:F8.

whether over exposing of your shot, it depends on your OVERALL reading... not base on 1 main light.... if u are having 1:2 of F16, your combine reading MAYBE between F16.3 to F16.6...

is u are using 1: 5 or 6, i advice u to use single light and reflector....

on negatives, overexpose 1 to 2 stops can be corrected when printing.... so long as u didn't under expose by more than 2 stop....

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