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Question: What is the 1 and 2/3 rule for studio lighting!?
I'm doing a studio portrait at university tomorrow in the studio and am still a bit uneasy about the light metering rules, especially since digital cameras have many f-stops between!. I want to get a stock standard portrait before I get creative with the lighting!. I'll be using a soft box, hair light and background light!. Can someone please explain it to me!? Www@QuestionHome@Com


Best Answer - Chosen by Asker:
A 3:1 lighting ratio has a 1 stop difference between the key and fill light!.

Picture it this way!. Place the main or key light on one side, your choice right or left, so that it lights one side of the face fully and partially lights the other side!. Then place your fill light on the lens axis, above and behind the lens!. The lens is usually set at eye level, the fill light behind and above it!.

Adjust the power to your lights so that the key light is twice as bright as the fill that is, one stop brighter than the fill light!.

Now you have 2 units of light from the key light and 1 unit of light from the fill light!. The fill light puts 1 unit of light on the shadow side of the face and on the highlight side of the face at the same time because of its position at the lens axis!.

One unit of light from the fill on the shadow side and 2+1 units of light from the key and fill lights on the light side of the face!. A 1:3 lighting ratio!.

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If you have time, play around a bit, but plan it out and take notes!.

The idea with a ratio light that is that you want some shadow, but want to control it so that it is not too much!. As stated, that means you have to put light on both sides of a person's face - normally directional!. You have a softbox, so that might be 45 degrees to the right, and a hairlight and a background light!. Any thoughts on how you will light the other side of the face!?

The good news about a fill light is that you can often use a reflector to light that other side of the face!. Many school studios use a lot of foamboard - white board that will refect light from the main light back on to the subject!. It often has to be quite close to get the lighting you need, but it works!.



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The 3:1 lighting ratio is just a guideline for "standard" portraiture and is the difference between the key and fill lights in light intensity!.

If you are shooting dramatic portraits, high or low key, then all that goes out the window!. Some beginning photographers go to the extent of using certain length stings to set up their flash units in relationship to the model (client) with taped marking on the floor to remind them where to place the posing stool, key and fill light!.

The pros, just look at the light and shoot!.Www@QuestionHome@Com