Metering when using fill

Hoping someone can clear this up in my head. I have read that when

using a main and a fill you should meter only for the main, with the

fill turned off.

 

1. Is this correct? (Because I have also read that I should meter

the exact light that's hitting the subject, which to me means the

fill light should be on while metering, with the dome pointed at the

camera.)

 

2. If it is correct, would the fill light not add to the main to

create an overexposure in places when the photo is taken? I'm

thinking that an f8 main plus a f5.6 fill creates more than an f8 in

total - which spells hot spots to me.

 

Perhaps I'm just misinterpreting. Perhaps when he instruction

is 'meter the main' they are just saying "point the dome directly at

the main, not at the fill or the camera". I could "perhaps" myself

stupid here...

 

Can anyone explain, and 'perhaps' give an idea about where I should

point the meter.

 

Many thanks.

Polaroid!

<cite>would the fill light not add to the main to create an overexposure in places when the photo is taken? I'm thinking that an f8 main plus a f5.6 fill creates more than an f8 in total</cite>

<p>

Yes, they combine. The math for figuring it out is the square

root of the sum of the squares, same as the pythagorean theorum

for the length of the hypotenuse of a right triangle. So an f/8

main plus an f/5.6 fill combine to make f/9.7 where they're

both shining. That's about a half stop more light

than the main by itself, which isn't terribly important for

color negative film. If your fill ratio is deeper (e.g. f/8

main and f/4 fill), the fill will add relatively less.

So maybe the difference between metering the main alone

or metering the main + fill is so small it's academic.

<p>

There are various conflicting systems, with adherents

to each of them managing to produce relatively well-exposed photos.

The only folks who are outright wrong are the ones who

say "you absolutely MUST do it exactly the way I learned

to do it". As long as you're consistent, you should be

able to make any of the popular methods work.

<p>

One way which is simple enough to understand, and which works

well, is to meter each light separately when setting ratios,

but use a combined reading for final exposure determination.

When adjusting ratios, point the meter at the light you're

measuring, and either shade it from the other lights, or

turn the other lights off. Once you've got the lights

set in the ratio you want, then take one final reading

of the combined setup, pointing the meter toward the

camera. Use this reading to set the lens

aperture. This is by no means the ONLY way to work, and

it's probably not the fastest way to work, but it's

one way which should give reasonably consistent results.

<p>

Also, if you do this a few times, you'll clearly see

the difference between the readings when you meter main alone

versus main+fill, since you will have measured both.

Maybe after awhile you'll decide it's ok to shortcut somewhat.

Ellis...Polaroid!! If I do that I may as well completely give up learning this stuff and go digital!! OK I'm kidding. I love digital. Like I love Salma Hayek...lustily, from afar...

 

Richard...thank you. That's actually the first really clear explanation I've read. I find so many sources assume a basic knowledge of the theory and jump right into the mathematics. Some of us just need the instructions like "Do A, then B then C and you'll be fine". Lesson very much appreciated.

"Polaroid ! If I do that I may as well completely give up learning this stuff and go digital !!"

 

Robert,

 

The best way to learn any technique is by trying it. The instant feedback from test polaroids or digital capture is the ultimate visual aid for learning proper exposure, composition, lighting, posing, etc.

 

Shooting test Polaroids would be an excellent way to improve your lighting techniques. Shooting digital tethered to a computer would be even better because the image on the computer screen is bigger and has better color and tones than a Polaroid.

 

There's a reason that professional commercial photographers shoot Polaroids on every job involving lighting. It's the smart thing to do and ensures the best results. Digital capture is even easier to use to judge and tweak lighting.

Polaroids will show the look of the lighting, for the most part, but that's about it to the untrained eye. The response of Polaroid material is different enough from the film you will probably be using, that you will need experience reading Polaroids. Digital tends to be much, much closer to WSIWG.

I do fully understand the value of instant feedback, whether through Polaroid, digital, or those glares I occasionally get from my wife when I say something stupid.

 

I would gladly use digital, and likely will some day, I just can't afford it at the moment (apparently I have to make mortgage payments every week - don't these bank people know I have a hobby?).

Point directly at each light individually, and meter each individually from the position

of the subject, while shielding it from all of the other lights. You can use your hand

or a tube to do the shielding. You can also turn off the other lights. Then later, you

can do a more general meter reading with the meter unshielded with all of the lights

on.

 

If the object has sheen, then simply pointing the incident meter at the light won't do

the job. If the object is a person, you will be using reflectors which will add efficiency

to these mains. This is more complication.

 

You sort of need to do a 1st level, then a 2nd level, then a final check exposure for

your work. You first expose for each light. Then add reflection and combine lights-

exposure meter again. You make aesthetic adjustments, then you meter again. 3

times is a minimum and I suppose it could go higher the more perfectionistic you

become. The subject may move, the sunlight may change, you know. Then at the

end you want to know your total spread of light ratios so everything will show up on

newsprint. You find you are alittle spread out, so you then change your lighting to

compress things alittle. You could be metering 6 times!

 

Cochran' s answer is good. However, the addition of a polaroid actually

acknowledges other factors are present such as "sheen" and "overlap". If the lights

overlap very little, then their combination is not much of an exposure issue. You

wouldn't set your camera for their mathematical combination. Think of dramatic

fresnel lighting: the light may be spotty and uneven and have no broad areas of

"neutrality" or "mediumness" to anchor expose for. In terms of sheen, the light

hitting shiney objects or hair reflects off more or less light depending upon the angle

of the light: a mirror effect. This is hard to meter for. Therefore, the polaroid is

used for the evaluation.

 

The exposure meter takes you to one level; the Polaroid to the next, and digital, well,

to beyond! With digital's histograms and selective marking of over/underexposure

areas in the viewfinder, you have real time information there!

 

Cochran's answer is a beginning.

 

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