Light Meters: An Intro To The Light Meter

Intro

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                                            Source: Udemy.com

Due to digital cameras becoming increasingly more advanced, many beginning cinematographers, including myself at one point, believe that light meters are no longer necessary in order to capture well-exposed, cinematic images. With histograms, goal posts and predator vision built into your fancy, digital cinema cameras, why would you ever need a light meter? Well, I’m here to convince you as to why they’re necessary and provide you with a little info on how light meters operate and their history.

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Section I: Incident vs Spot vs Reflective Meter

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                                 Source: Lightcrafttech.com

When it comes to handheld light meters, there are two different types: incident and spot. An incident meter exclusively reads incident light (the photon beams that gracefully fall upon your subject or scorch them to death). How the incident reader works is you point your meter at the light while keeping it close to your subject. Then the Lumisphere, the white sphere that protects incident light intensity sensor (a little green chip on the board inside the meter), is hit with that light; that light is then passed on to the intensity sensor. From there, based on all of the settings you’ve manually programmed into the device, you’ll receive a reading in the form of an f stop; that f stop will be your guide as to how you will expose your actor/manipulate your contrast ratios.

What the incident meter doesn’t take into account is reflected light, which is how the light actually plays on every physical surface throughout the frame; for example, your actor’s skin. If your actor’s skin is a lighter shade, it’ll most likely reflect more light than a darker-skinned subject; the incident meter will not acknowledge that reflectance because it’s investigating only the light that’s falling onto the subject.

What the spot meter does is it adds the highlights, midtones, shadows and reflected light from the subject all into the equation. In turn, the meter provides the user with an f stop reading for every last inch of the frame, and that will allow him or her to make important decisions that will either make or break the image.

The third type of meter is the reflective meter, which is an in-camera meter that can read 25 to 30 degrees of an area. This type of metering helps the user see what is over or underexposed in the camera, but the metering does not provide the cinematographer or photographer with an accurate f-stop reading of any part of the frame. It is merely the camera communicating with you as to what’s occurring inside the sensor as it’s reading the light and shadow values of the scene. There’s more info on the reflective meter in section IV.

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Section II: History of the Incident Meter:

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                   The OG of light meters.  Source: bbc.co.uk

The first light meter, the Bee meter (invented by Alfred Watkins), was patented in 1890 and first produced in 1903; the meter was an actinometer, a pocket-watch-shaped device that measured the intensity of radiation via a photo-print-paper system that sat inside the meter’s circular crevice; the amount of time the paper took darken and the tint it turned were the calculations photographers depended on in order to acquire correct exposures. The meters came with speed cards that told its users how to utilize the meter in tandem with multiple types of film stocks. It was named the bee meter for its small size and highly efficient nature.

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(Extinction meter) Source:Tomowens.onepoint.co.uk

In 1947, the Mimosa America Corporation unleashed a new, revolutionary meter called the extinction meter. The meter was a plastic case that held six pieces of celluloid or neutral density, each a different opacity, labeled one through six; whichever number popped out at the photographer first was married to the wrap-around paper band that read different f stop, shutter speed and ASA combinations, which was fixed to the case.  The problem with this particular light meter is that once the user’s eye became acclimated to the device, all of the numbers would look the same in terms of light intensity, and extinction meter became useless. It was literally like trying to tell multiple shades of green apart from one another.

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      (L-398)   Source: Bhphotovideo.com

After the extinction meter was discontinued, light meters from 14 major companies including Gossen, Minolta and Sekonic all flooded the market with Spot and Incident meters, each touting how advanced their meters were to the masses. They released incident meters very similar-looking to the Seknoic L-398A. Today, Sekonic is the only real light meter company left on the market.

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Section III: History of the Spot Meter

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  (Pentax)   Source: Amazon.com

The first spot meter was created in 1935 by editor of the British Journal of Photography, Arthur James Dalladay. The meters were heavily dependent on Ansel Adam’s Zone system, which was created in the early ’30s. They started out as five-degree meters and, over time, evolved into 1-degree meters for precision; five degree meters are still available for use in a few modern meters.

The idea behind the spot meter was for the user to expose for the middle gray of the scene, which is zone 5 also known as 18 percent gray. The reasoning behind this is that zone 5 is the most neutral and the items we want to see in the image must neutral in order to be considered well exposed; subjects should never be under or overexposed.

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Section IV: History of the In-Camera Reflective Meter

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                                       Source: Blog.pond5.com

In-camera reflective metering was first introduced all the way back in the 1960s when Asahi Optical Co incorporated it into its prototype, 35mm photography camera: the Asahi Pentax Spotmatic, which was supposed include an in-camera spot metering system, but due to a difficulty in implementing the technology, was removed in favor of another type of metering called center weighted metering; how it worked is the camera would take a reading of the brightest and darkest object in the frame and expose for one. This particular exposure method would lead to underexposed subjects with perfectly exposed backgrounds or perfectly exposed subjects and overly exposed backgrounds. It was sort of a mess, and it still can be.

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                                         Source: mcpactions.com

Knowing that in-camera, reflective metering wasn’t technologically advanced or accurate enough yet to fulfill cinematographers’ exposure needs, cinema camera manufacturers Arri and Panavision cast it aside knowing that the more accurate, at the time, one-degree spot meters were available on the market; therefore, cinematographers needed to carry both an incident and spot meter while on set.

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Section V: In-Camera Matrix Metering In Cinema Cameras Today

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                                               Source: RED.com

In modern cameras such as the Alexa, RED and Sony cameras, especially RED, an internal Matrix Metering system is imperative in order to achieve an accurate exposure for their silicon-based sensors, and this is because each camera has a different digital film stock/dynamic range. Matrix metering is the camera dividing the scene up into multiple zones and then metering them for highlight and shadow.

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                                            Source: RED.com

The majority of cameras on the market include a matrix metering mode called false color. This method of exposure measures IRE (Institute of Radio Technicians) values -7 through 109. Purple represents underexposure, while red signifies overexposure.

Before, where the cinematographer would had to instinctually know what the camera wanted, the cameras now tell you precisely what they want, and that’s important because if you don’t fulfill the camera’s desired exposure, your footage is going to seriously chew through your post production budget due to denoising.

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Section VI: Using the Light Meter With Your In-Camera RGB Histogram and the Luma Waveform

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                                                Source: RED.com

The in-camera, RGB histogram is yet another tool that makes cinematographers’ jobs easier. Just like the in-camera spot meter in the RED, Alexa and various other cameras, in-camera histograms, which range from pure black to white, tell the user exactly if the sensor is over or underexposed. It also displays which colors are dominant throughout the spectrum, which is important because on silicon-based sensors, the color that must be present at all times is blue.

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                                 Source: Premiumupbeat.com

Some cameras, alongside the histogram, offer the use of the Luma waveform scale, which ranges from 0-100 IRE (Institute of Radio Electricians); this type of waveform combines all of the RGB channels into a single, white or green waveform for the cinematographer to view. Objects that are brighter than others will be located higher up on the IRE scale than items that are of lower exposure. It’s highly advised cinematographers use the spot/incident meter together with the Luma Waveform in order to attain proper exposure.

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Section VII: What Not To do When Exposing Your Camera

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 Source: Twitter.com

1. This is a biggie. Never expose your camera based on screen brightness. Your images will either come out over or underexposed, and you’ll be confused as to why. Read the camera’s histogram or waveform.

2. Do not use your light meter without consulting your in-camera RGB histogram. Your light meter may be able to accurately measure light with the precision of a brain surgeon, but each digital camera is different, and light meters do not automatically adapt to different cameras; they read light, and that’s it. If you want to sync your meter to your camera, Sekonic offers that option with its DTS software where you can profile your camera on your computer and download the information to your light meter.

3. Do not use the camera without consulting your meter when measuring contrast ratios. Even though your camera includes a state-of-the-art internal matrix-metering system, it cannot read incident light or accurate f stops. Don’t guess your contrast ratios; mold them to what you and your director believe the scene requires.

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Conclusion

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(Sekonic L-758C) Source: Camerainthepost.com

Light meters are powerful, calculative tools that grant cinematographers and photographers a systematic method of controlling light throughout the frame. Without them, lighting would become a game of guesswork and a gateway for even more insecurity on set. The camera and light meter balance each other out, so when on set, use all the tools (in the camera and on the light meter) available to you so you can put your mind at ease and create that aesthetically heart-pounding image you’ve always wanted.

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