Portrait studio lighting ratios

[buck_rogers1]

I'm just starting in on strobe/studio portraits and I'm unsure of the

ratios I should set for my lights.

 

I have two Vivtar 283's an Excalibur 3200 monolight. I meter with a

Seikonic L358 and shoot NPC through my Eos-1.

 

What EV difference should there be between the main/key, fill, and

hair lights to get detailed shadows and highlights. How much EV

difference will the final print be able to show? Can anyone show me

some examples?

 

I have been shooting using the f-stop value metered from the fill and

key light together. (I will try to post some examples when I get some

scanned)

[jkantor]

I think it's something you'll want to learn (and decide) for yourself through experimentation. There's no one setting for all subjects, moods, and styles.

 

As for the print, if you scan and print digitally, you'll have different chractacterisitics than if printing traditionally.

[mikecat]

Buck, I assume that when you say, "I have been shooting using the f-stop value metered from the fill and key light together.", you mean that you are AVERAGING the fill and main light values. If this is the case, I woud recommend that you use the f/stop value you get from you main light only as your actual exposure setting. The reson for this is that the main light is the one that actually provides the light for the subject. The fill light is there to adjust the shadows, so it should always be less than the main light.

 

I agree, you shoudl experiment to see what you like. But, a good starting point is to use a 3:1 light ratio (roughly 1.5 stops difference between main & fill). Try 2:1 (1 stop diff.), 4:1 (2 stops diff.) even 9:1 (3 stops diff.) to see what you like.

[brooks short]

Buck,

 

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 the lens.

 

Adjust the power to your lights so that the key light is twice as bright as the fill ie: 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. But 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.

 

You can also do a lot with just one light and a fill card. By placing the fill card closer or farther from the subject you can control the value the shadow side of the face quite effectively.

 

Here's an example using just one strobe bounced into a 42" umbrella from the right side and a fill card on the left just out of view. I used no background light Because the main light was a large umbrella some of the its light spilled onto the background. What looks like a background light effect is just a corner burn on the print.

 

Experiment and find what you like.<div></div>

[buck_rogers1]

Thank you all for your input. I think Brooks got at what I was really trying to ask. Strobes have an additive quality so if the two overlap, the net exposure equals the sum of the individuals right? 2EV(key)+1EV(fill)=3EV

 

Thanks for the image as well, nicely done.

[brooks short]

Buck,

 

Thanks.

 

Here's something else to consider. Light ratios are just that, ratios and they work with strobes or hot lights.

 

So you can accomplish a 1:3 ratio with hot lights where one light is twice as bright as the other and they are at the same distance from the subject or with lights (strobes or hot) that are the same power but at different distances.

 

For example if you have two lights of the same power, and your fill light is 8 ft. from the subject, at what distance should you place the main light so that it is twice as bright as the fill ?

 

Think of the distances as f-stops instead of feet (or inches or cm or meters etc. If the fill is at 8 ft , another light of the same power is twice as bright if it is placed at 5.6 ft from the subject.

 

Place your fill at 5.6 ft. and the main light would have to be at 4 ft. to be twice as bright. 16 ft. for the fill and the main light should be at 11 ft, etc.

 

So there you go, pretty simple don't you think ? #8^)

[joe_garrick]

<I>Think of the distances as f-stops...</i>

<P>

Or multiply or divided by 1.414 (the square root of 2) if your distance doesn't land neatly on an f-stop.

[markskelly]

Brooks and Joe, you guys just blew my mind. I never realised the logic behind the

f-stop scale in that way before. Yep, the inverse square rule in action. Fantastic.