Various ways to use an incident light meter

Rick A

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The domed cover measures "omnidirectionally" and includes extranious light. The flat cover is used by aiming it directly at the light source(not the camera)to ascertain the illumination ratio. No, you dont need the flat cover, but if you are a stickler for perfection and need to know the actual lighting ratio, use it.
 

markbarendt

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Normal dome 180° vertical x 180° Horizontal

What it doesn't normally see is 360° x 360°
 

Galah

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benjiboy said:
The dome can't "see 180 degrees" 2F/2F because it can't see behind the meter body...
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The dome does, actually, have a 180 degree field of view, what it doesn't have is a 360 degree field, and what would be the point of having that?
 

John Koehrer

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The flat disc is also used for checking exposure for flat work(art). by checking each corner & center it tells you if the light is even edge to edge.
 

benjiboy

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Galah said:
The dome does, actually, have a 180 degree field of view, what it doesn't have is a 360 degree field, and what would be the point of having that?
Click to expand...

The point would be that if the incidental light receptor could "see" around the meters body 360degrees it could evaluate the backlight as well as the frontlight at the same time, thus avoiding having to taking two readings and averaging them.
 

markbarendt

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benjiboy said:
The point would be that if the incidental light receptor could "see" around the meters body 360degrees it could evaluate the backlight as well as the frontlight at the same time, thus avoiding having to taking two readings and averaging them.
Click to expand...

I'm struggling to see a reason for that type of averaging.

Can you give a practical example demonstrating the advantage?

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The reason that a normal incident meter's dome is hemispherical is to be able to meter for the light falling on a 3D subject.

It is designed to "read" (average?) the way the "dark" & "light" parts of the side visible to the camera are lit and (thankfully) ignore back-lighting/reflected light.
 

benjiboy

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markbarendt

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I think I see what you are suggesting; basically, by duplexing the reading you are making a decision to add more importance/consideration to the background and improve it's detail.

That's a valid exposure decision. And yes, averaging a "normal" incident reading against a contrasting background reading, dark or light, would add available detail in the background but it also skews where the main subject falls on the film's curve.

For me, a normal incident reading places exposure properly. The main subject always trumps the background and I'm generally happy to let the background fall where it falls.

I only adjust the camera to "place" the background exposure when I'm using artificial light to "place" the main subject's exposure.
 

benjiboy

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All I can say Mark is it works for me
 

2F/2F

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Hi,

I don't understand this statement. The dome does indeed gather light from a 180 degree area. How to most effectively place those 180 degrees of coverage in different situations is the topic of the thread.

Also, the quotaton you used was not written by me. I said:

2F/2F said:
The dome, covering 180 degrees, takes that flare/spill into consideration. This is why I prefer it to the disc for measuring lighting ratios.
Click to expand...

As for your second post, in which you used "360" instead of "180" – Was the first "180," that I quoted above, a slip, when you meant to write "360?" – averaging a main light and a back light gives you an underexposed main subject and an overexposed background. Each ends up under-or-over exposed by half the difference between them. It is in somewhat the same way that taking a down-the-middle-toward-the-camera reading in ratio lighting results in overexposure of the film by half the difference between the two readings.

If you want to bring the background down in tone without burning/dodging, and you have control of your light, you just need to add more light to the part of the main subject that is visible in the picture. That way you can bring down the background without underexposing the main subject.

In a backlit situation in which I might want to bring down the background, but I am working with uncontrolled light, I still expose for the subject and burn the background when printing rather than underexposing the main subject in order to make the background print better. Either way you have to burn or dodge, but digging good tonality and detail from an underexposed main subject is much less likely to succeed than digging good tonality and detail from an overexposed background.

But you are obviously set on your method, so I will just say as a tip that to do that, you don't even need to take two readings. Just place the dome parallel to the imaginary plane that runs between the main light and the back light and you have a one-step directly-readable average of the two lights.
 
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benjiboy

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The book I quoted The Exposure Manual by Dunn and Wakefield shows a series of pictures on Kodachrome of the authors wife taken outdoors in sunlight at hourly intervals throughout the day using this Duplex Method, and every one is correctly exposed, I've used this method ever since I first read the book about a quarter of a century ago with various light meters, and all I can say is it works for me.
 
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markbarendt

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I want to say again that I have no problem with your use of that technique, nor do I doubt your success in using it.

That averaging method is essentially a way of applying "weighting" principles to an exposure decision, much like an automated matrix meter tries to do.

But, for your statement to be true
benjiboy said:
every one is correctly exposed
Click to expand...
one needs to make the assumption that there is one "correct" exposure for any given shot.

One correct exposure setting for a given shot has never been the case for photography as a discipline.

Exposure placement is an artistic or technical endeavor to get a locally defined result.

You and I will almost always place our exposures in different spots, no foul here either way, you and I just "weight" what's important differently.
 

2F/2F

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If making the background darker at the expense of making everything in the shot darker is important to you, then that is one way to do it. But to simply say that it is the correct exposure is not quite right. It is only the correct exposure if you have decided that having two different parts of the picture incorrectly exposed equals having the whole picture correctly exposed. You end up with a background that is overexposed, and also end up with a main subject that is underexposed. Exactly the problem with averaging and with in-camera meters, exactly what you are trying to get away from by using an incident meter, and exactly why it is such a bad idea in most cases.

It would be much better to simply shoot in different light. Why put someone in the shade up against a bright background with no fill light if you do not want the background to be bright in the photograph? Why are you shooting a person if you are not exposing for them, unless your aim is specifically to not show what the person looks like (perfectly fine, but not standard)? It's at best an artistic decision that results in a darker-than-normal subject, and at worst a sloppy compromise to work around inattention to lighting.

I am sure you get printable results, especially in situations in which the background is not that much brighter...but not ideal results.

And I am still wondering about the statement that the dome does not take in light from a 180 degree field.
 
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benjiboy

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2F/2F Western actually made a prototype meter with two hemispherical sensors one facing forward and the other backward they called The Janus after the Roman God who was the keeper of gates who had two faces one facing forward and one back to take a single reading for
the Duplex System, although I admit it was never manufactured, I thought it may be of interest to some members.
 
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