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Light Meter: Do you use spot or incident?


Wendy Sanders McDonlad
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8 minutes ago, David Mullen ASC said:

When shooting dramatic scenes with coverage, exposure and contrast consistency from set-up to set-up can matter more than getting the exposure exactly right -- so while a spot meter can be more precise, it can be too precise, causing you to vary your exposures shot by shot, set-up by set-up, so individually each shot is correctly exposed perhaps but when cut together, you can see the exposures being "corrected" on each shot -- for example, if an actor is sweating in a scene and if their skin gets more shiny on some takes, the spot meter might tell you to stop down because the face is getting a stronger hot spot from the sweat. And again, in each set-up in a room, there may be different subjects and objects in that frame so it is simpler to decide what the light levels you want in each part of the room and then let the objects fall where they may when they move through that light.  So you might light a room where in the center under a chandelier, the light is one-stop overexposed based on an incident meter reading and then around the edges of the room, someone is two-stops underexposed. Then when you shoot coverage and if you have to do any relighting, you can start knowing what the levels were in the wide shot that you have to match to.

this is a great point.

 

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https://www.thoughtco.com/difference-between-accuracy-and-precision-609328

Though it is hard to articulate, some of the differences in metering technique is the difference between accuracy versus precision. I guess what I'm advocating is precision over accuracy (?), I want a method with consistent results in different lighting situations rather than be overly accurate about exposure on a shot by shot basis.  So you need a metering system that gives you repeatable results and yet takes into account the variations of tonal value in real life.

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10 hours ago, Wendy Sanders McDonlad said:

If you light it from the incident reading it will be completely off, since the fabrics is not nearly as reflective.

An incident meter measures the light falling upon a subject, and gives you a reading for a hypothetical 18% gray. If you expose per the meter, then every object that is lit by that source will be exposed properly in relation to the gray. That’s why incident meters are so useful, because they take no account of the subject, so you don’t need to figure how many stops over or under the reading an object should be.

if you point a spot meter at a black object, the reading you get will be to expose the black as 18% gray, so you need to know how much darker black is than gray, and adjust your exposure accordingly. Spot meters see everything as 18% gray. If you don’t know how to interpret the readings, your exposures will vary wildly.

 

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I have spot and incident meters. I use the incident meter to light the set, and when I used to shoot film, I used the spot meter to set the camera exposure, though I also sometimes use an incident meter to set exposure, depending on the situation.

with digital cameras I still use the incident meter to light the set, but I generally use the camera image or waveform to set the camera exposure.

Since I also use film cameras for shooting stills (off set), my spot meter is my go to meter for shooting stills, on film 🙂

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  • 2 weeks later...
On 8/31/2020 at 1:14 AM, Stuart Brereton said:

An incident meter measures the light falling upon a subject, and gives you a reading for a hypothetical 18% gray. If you expose per the meter, then every object that is lit by that source will be exposed properly in relation to the gray. That’s why incident meters are so useful, because they take no account of the subject, so you don’t need to figure how many stops over or under the reading an object should be.

if you point a spot meter at a black object, the reading you get will be to expose the black as 18% gray, so you need to know how much darker black is than gray, and adjust your exposure accordingly. Spot meters see everything as 18% gray. If you don’t know how to interpret the readings, your exposures will vary wildly.

 

Stuart makes an important point here regarding the spot meter reading any color or surfaces as 18% gray.

Try to think of both meters as information gathering tools that you will interpret through experience and analysis rather than f stop determining devices. Your mind gathers the information, and you can modulate the various source values through various means at your disposal to determine the final contrast and esthetic result you desire.

Hope this isn't too "zen" and makes sense to you Wendy.

 

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Reflected meters are like kangaroos with ADHD, powerful but all over the place and hard to work with. Incident meters are like an old friend who will always tell you the truth even if it hurts.
 

An incident meter cannot be fooled by extra dark or extra bright objects in the scene. With reflective meters it happens all the time and you have to learn to work around that weakness which takes time and experience.
The classic example is a Caucasian bride in a white dress standing next to a Black groom in a black tuxedo. If use a reflected meter neither will be correctly exposed. Scenes with big areas of white sky also fool reflected meters.
The problem with spot meters is that you’re depending on the easily fooled human eye to choose what to point the meter at. It works well if, like Ansel Adams, you shoot outdoors in locations you’re familiar with or in studios. 

Incident meters just tell you what is happening without any interpretation. Then it’s up to you to adjust the lights, prop colors, makeup tones, and scenery colors to create the tonal relationships you want. 

Edited by Marcos Cooper
Metaphor
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  • 2 weeks later...

The danger of sacrificing consistency in trying to get perfect exposure is a real danger. 

Bearing that in mind, here's what Gerald Hirschfeld, A.S.C. has this to say in his article on Exposure Meters and The Cinematographer.

Using a Spot Meter, the Final Exposure Check

Quote

 

Feature films demand a high degree of technical excellence, starting with lighting and exposure. To accomplish this standard, in a large set with action, the DP may check exposures of featured actors in various parts of the set by taking a third reading using a spot meter which can follow the action. A spot meter with an angle of acceptance of only 1° will offer an exact exposure of a face by itself at any distance up to about 35 or 40 feet.

Be aware not to read strong highlights if the actor perspires a bit. Spot meter readings can be made during rehearsals or even during filming as they are generally made from the camera position. This is a big advantage in saving time andobtaining a final check for the correct exposure. Although color negative film has a wide exposure latitude, using the correct exposure to obtain a normal density negative helps to get the best print, particularly when special lab processes are requested.

 

 

Hirschfeldonmeters.pdf

Edited by Marcos Cooper
Ampliflying caution about over-precision
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