by David Tamés, v.2, revised October 11, 2023
In this presentation we’ll focus on technical craft terms and concepts: Role; Contrast ratio; Quality; Intensity; Direction; Beam size; Beam pattern; Distance; Color; Source.
In the Lighting Visual Storytelling presentation we focus on visual storytelling: What motivates the lighting? What mood does it set for the scene? How does it enhance the storytelling?
There are multiple places along the pathway of light that have an effect on your exposure. This presentation focuses on scene illumination. Setting exposure and all of the factors after scene illumination in the pathway of light that have an effect on the final exposure is covered in the “Camera Fundamentals” presentation.
The pathway of light: 1. Scene Illumination, 2. ND Filters, 3. Aperture, 4. Shutter Angle (shutter speed), 5. and finally, the sensor. Sensors have a native ISO and any values above or below this sensitivity are achieved by a gain circuit after the sensor. NOTE: The native ISO of the Sony a7iii camera in the Sony Video Kit is 800, you’ll get the best image quality at this ISO. ISO is a number that refers to your camera’s sensitivity to light. A lower ISO means means less sensitivity, a higher number means more sensitivity. Basically, raising the ISO increases the sensitivity of the camera.
The higher we move away from the base ISO, the less light we need to get a properly exposed scene but also more noise will be introduce into the image. In most cases, it's better to add lighting to the scene if you can or open up the aperture if you can; these options are better than cranking the ISO setting above the base ISO since all you are doing is adding electronic gain to the signal. You can get away shooting at higher ISO, but if you want to have the highest quality image the camera is capable of producing, you should shoot at the camera’s ‘Base’ ISO, or ‘Native’ ISO whenever possible. Some cameras have multiple base ISO, providing optimized performance at a high ISO in addition to a low ISO.
Contrast ratio is the difference (in terms of intensity) between the brightest and the darkest portions of the image is called the contrast ratio. The difference in the intensity of your key and fill has a significant effect on the the contrast ratio of the scene.
A low contrast scene has a low key to fill ratio, a high contrast scene has a high key to fill ratio, for example: 1:1 is flat lighting, without any definition, 2:1 is pretty standard for television studio lighting for news and talk shows. 3:1 or 4:1 provides nice dimensionality to a scene, 5:1 or 6:1 starts to become seriously dramatic (e.g. film noir).
Scenes can be described as high key (free from dark shadows) or low key (significant portion of the scene in shadow) lighting scenarios:
High key lighting: difference between brightest and darkest portions of the entire scene is low, but the scene itself is bright and cheerful. Another way to define high key is over 50% of the frame area is over middle grey, not a lot of dark shadows. The contrast ratio is typically 1:1 or 1:2.
Low key lighting: difference between brightest and darkest portions of the entire scene is high. The contrast ratio is typically 16:1 or greater. Another way to define high key is over 50% of the frame area is under middle grey. Lots of black and shadows.
The quality of the light depends on the size of the source relative to the subject. We talk about hard, semi-hard, and soft light sources. Direct sun behaves like a point source, it is very hard, casting crisp shadows, with very little wrap around a face. On the other hand, a large window facing the northern sky without direct sunlight is a very large soft source, casting soft shadows and wrapping gently around a face. We can also think of quality beyond hard/soft, for example: direct/indirect, sourcy/ambient, chiaroscuro/flat, strong/gentle, crisp/wrapping, focused/general, etc. The quality of light along with the contrast ratio are highly influential in setting the mood and atmosphere of a scene.
Soft sources: cloudy day, bounce card, soft box, lantern, hard source through diffusion, etc. / difficult to control with cutters, therefore grids are used on soft boxes for spill control instead of cutters. Soft source characteristics: Soft-edged or no shadows; de-emphasizes surface; texture and detail; difficult to control (cutters don’t cast distinct shadows unless very close to the source, e.g. grid).
Hard sources: direct sunlight, Fresnel, PAR, spotlight, ellipsoidal, small light bulb or candle, etc. / easy to control with cutters and gobos. Hard source characteristics: Focused beam; distinct shadows; accentuates surface texture; easy to control (cutters cast distinct shadows).
Large sources provide a soft quality with a nice wrap much like window light. Why do professional productions use large, very bright sources farther from the subject instead of using a smaller unit closer to the talent? Because this allows for less falloff per foot due to the inverse square law and a nicer wrap around faces. The combination of the large hard light softened by the diffusion frame provides a directional key light that gives the scene dimension that would otherwise look flat on this overcast day.
Color temperature is a way to describe the color of light sources, particularly the color of white light. Color temperature is measured in units called kelvins (K). Light sources emit a spectrum of colors. Color temperature describes the color appearance of the light source based on this spectrum. It's especially relevant when discussing white light sources. The Kelvin scale ranges from lower temperatures (described as "warm" or "yellowish" light) to higher temperatures (described as "cool" or "bluish" light).
Common color temperatures: Candlelight approximately 1,900 K // Golden Hour approximately 3,200 K // Bright White LED used in contemporary interiors, approximately 4,200 K // nominal daylight, approximately 5,500 K // overcast approximately 6,500 K (more blue due to more light from sky) // heavy overcast day even bluer at approximately 9,000 K
Planck’s Law describes the spectral distribution of radiation from a blackbody, a theoretical lamp filament (the closest equivalent to this in the real world is the filament of an incandescent light bulb) that absorbs all incident radiation and emits it as thermal radiation. A blackbody's spectral distribution depends on its temperature. Color temperature is a concept derived from blackbody radiation used to describe the color of light emitted by the blackbody radiator at a specific temperature. The color temperature of a light source describes the spectral response of a source that is on the line from reddish/orange via yellow to more or less white to blueish white light in units of K (degrees Kelvin). 0° K = -273.15° C. Artificial light sources are categorized by their color temperature, allowing users to select lighting that matches their intended aesthetic or desired color quality.
Color temperature is a way to describe the color appearance of light, ranging from warm to cool, using the Kelvin scale. It plays a significant role in various fields where the quality of light is essential for achieving desired aesthetics and accurate color representation.
The two common standard color temperatures for film and video lighting are “Tungsten” at 3200K and “Daylight” at 5600K. Knowing these two numbers will go a long way to helping you create images that are balanced for your light source as proper white balance will make color correction go better in post.
Setting the correct white balance ensures that whites appear truly white, without color shifts since your visual system compensates for color casts but the camera does not. Color temperature also plays a role in creating specific moods or aesthetics. Incandescent bulbs have a warm color temperature (typically around 2700K). Daylight is often considered to have a neutral color temperature (around 5600K on a sunny day).
Fluorescent lights can vary in color temperature but are often cooler in appearance (e.g., 4000K to 6500K). LED lights come in a range of color temperatures, making them versatile sources of illumination. Most professional lighting units with a fixed color temperture provide Tungsten/3200K or Daylight/5600K. Bicolor units offer variability between warm to cool colors including Tungsten/3200K and Daylight/5600K. RGB units allow you to adjust the unit to produce a wide range of hues. RGBWW units (designed with Red, Blue, Green, Warm White and Cool White LEDs) provide better color rendition than RGB lighting units. Gels can be used to change or fine-tune the color temperature of fixed color temperature units.
The name tungsten comes from the filament made of tungsten sealed in a glass envelope filled with a mixture of an inert gas and a small amount of a halogen, such as iodine or bromine used to make what is commonly called “quartz-halogen” or “halogen” or “quartz” lamps. The combination of the halogen gas and the tungsten filament produces a halogen-cycle chemical reaction, which redeposits evaporated tungsten on the filament, increasing its life and maintaining the clarity of the envelope. This also allows the filament to operate at a higher temperature than a standard incandescent lamp of similar power and operating life. The small size of halogen lamps compared to ordinary incandescent lamps also permits their use in compact lighting instruments. These factors contribute to the wide use of 3200K quartz-halogen lighting in film/video production until recently when LED cost/performance began to exceed the cost/performance of quartz-halogen lighting.
Nominal “Daylight” is 5600K but varies in nature and depends on whether you are in the shade or direct illumination as well as the time of day and the level of atmospheric pollution (smoke from wildfires make for dramatic sunsets). Note that the wall in the room shown on the right is “Phillipsburg Blue,” a deep blue color, however, it appears dark with green tones due to the warm interior lighting which is rich in the red wavelengths of the spectrum but deficient in the blue wavelengths, thus changing the appearance of the color of the wall on video.
Spencer Finch: Cosmic Latte (2017), 150 light fixtures and 417 incandescent bulbs, dimensions variable. Features over 150 specially fabricated LED fixtures suspended from the ceiling over an expanse of the 80-foot long gallery. The constellation of LEDs are arranged in the gently arching shape of the Milky Way as it is observed in the Northern Hemisphere in March. The work’s title, Cosmic Latte, refers to the name of the average color of the universe, which in 2009 was determined to be more beige than what has been traditionally thought of as blue. Two American astrophysicists studied the color of the light emitted by 200,000 galaxies and created a cosmic spectrum, which they then blended according to the light spectrum visible to human eyes. Finch represents that specific warm, yellowish-white shade of light with LED lights (designed to look like incandescent bulbs), which are then arranged in the shape of the molecular models of the pigments needed to create this “cosmic latte” color: titanium white, Mars yellow, chrome yellow, and a touch of cadmium red. Text source: MASS MoCA
Note how warm the gallery lighting appears on video when we set the camera white balance setting to 5600K daylight. The D65 standard represent average daylight with a correlated color temperature of approximately 6500 K. CIE standard illuminant D65 is used in colorimetric calculations requiring daylight and is the target white point for computer display, for more information see Illuminant_D65 (Wikipedia). This also illustrates the role of the color of ambient illumination in how we percieve objects in the scene, note how different the painting looks on the computer display and on the wall (the AR overlay notwithstanding). This brings us to the topic of color rendering, spectral distribution, and the color rendering index.
The emission spectrum of light sources (often described as spectral response which is not quite accurate) describes specific wavelengths produced by a source of illumination. This is important because photosensors are sensitive to a wider range of wavelengths than what the human eye sees and the spectral response influences how we perceive the color of objects under illumination. Note how daylight is rich in blues while tungsten lighting is right in reds and a typical white LED source has a peak in the blue region and an uneven color response overall. Some high end LEDs designed for professional film/video/photo applications have a smoother response.
Color Rendition: Color temperature also affects how colors are perceived. Light sources with different color temperatures can make the same object look different in terms of color. This is why color rendering properties are important when selecting light sources for tasks where accurate color perception is crucial. Light sources with different color temperatures can affect how colors appear in video and everyday life. High-quality light sources aim to have a color rendering index (CRI) that closely matches natural daylight. CRI is a quantitative measure of the ability of a light source to reproduce the colors of objects faithfully in comparison with an ideal or natural light source.
Problems have been encountered attempting to use LED lighting in digital cinema production since the color spectra of LED lighting primary colors does not match the expected color wavelength bandpasses of digital sensors. As a result, color rendition can be unpredictable, therefore, various other metrics such as the TLCI (television lighting consistency index) have been developed to replace the human observer with a camera observer. Similar to the CRI, TLCI measures quality of a light source as it would appear on camera on a scale from 0 to 100. Some manufacturers say that their products have TLCI values of up to 99.
Source: Color_rendering_index (Wikipedia)
We can spread the beam of light to soften the source using various types of diffusion: Tough Spun, Full Diffusion (Lee 216), Half Diffusion (Lee 250), Frost. Also available: Grid Cloth, Tough Silk, Soft Diffusion. Silks on frames are common or use a silk that’s part of the 5-in-1 Flex Fill.
CTO gels are used to warm a light source:
Full CTO converts daylight (5500K) to 2900K
1/2 CTO converts daylight (5500K) to 3800K
1/4 CTO converts daylight (5500K) to 4500K
1/8 CTO converts daylight (5500K) to 4900K
CTB gels are used to cool a light source:
Full CTB converts tungsten (3200K) to 5500K
1/2 CTB converts tungsten (3200K) to 4100K
1/4 CTB converts tungsten (3200K) to 3500K
1/8 CTB converts tungsten (3200K) to 3300K
Plus Green and Minus Green gels are used for correcting green or magenta color casts. TIP: a touch of minus green on backlights when doing green screen helps neutralize the green spill from the green screen).
Minus Green (Magenta):
Full Minus Green reduces green, nominally equivalent to CC30 Magenta.
1/2 Minus Green reduces green, nominally equivalent to CC15 Magenta.
1/4 Minus Green reduces green, nominally equivalent to CC075 Magenta.
1/8 Minus Green reduces green, nominally equivalent to CC035 Magenta.
Full Plus Green adds green, nominally equivalent to CC30 Green.
1/2 Plus Green adds green, nominally equivalent to CC15 Green.
1/4 Plus Green adds green, nominally equivalent to CC075 Green.
1/8 Plus Green adds green, nominally equivalent to CC035 Green.
The selection of a gel colors is a creative process, everyone sees colors in a slightly different way. Gel sheets are used primarily to change the color of a light source. There are several categories of gels, including color effect, color correction, diffusion, reflection, LED, and scrim. Vendors provide swatch books that allow you to see and experiment with the wide range of gels available. There are several manufacturers of gel sheets used in film/video production including Lee Filters and Rosco.
The major categories of gels include:
Gels are available in many different sizes, the most common are 21 by 24 inch sheets and rolls that are 48 inch wide and 25 feet long.
The Lee Filters numbering system is widely used in the industry. The handy Lee Filters "Swatchball" has been replaced with the "Lee Swatch Book App” available for iOS and Android. This app has the complete range of Lee Filters on one screen, with a color picker so you can build and save palettes. Another way to view the full line of Lee Filters products is to order a Lee Filters swatchbook which has a small (roughly 2 inch by 1/2 inch) sample gel sheet for each gel. A standard polyester gel sheet should sustain temperature up to 180°C/356°F. A high temperature gel sheet should sustain temperatures up to 280°C/536°F. Gel sheets are made from a few different types of materials. Standard gel sheets are made from a very thin polyester material. The gel sheets can be cut down to whatever size dimensions you should need.
Some common filters: Lee 106 Primary Red strong red effect. Good with cyclorama lighting; Lee 071 Tokyo Blue a deep blue used for midnight scenes and cyclorama lighting; Lee 104 Deep Amber Lighting good for sunlight effect, accents and side light; Lee 181 Congo Blue looks like black light when used with a fluorescent source; great effect color; Night Blue; Skelton Exotic Sangria; Bastard Amber; Dark Bastard Amber; No Color Pink; Surprise Pink; No Color Blue; Special Lavender;
Diffusion/ND commonly used without changing color: Lee 216 White Diffusion a strong diffusion used for soft effect lights; Lee 209 0.3 Neutral Density reduces light 1 stop; Lee 211 0.9 Neutral Density reduces light 3 stops, without changing color; Lee 299 1.2 Neutral Density reduced light 4 stops, without changing color.
LED Correction: Lee 808 Zircon Warm Amber 6 offers major warm up correction of cool white LED; 3500K LED to 3000K; Lee 807 Zircon Warm Amber 4 offers major warm up correction of cool white LED; 4000K LED to 3000K; Lee 806 Zircon Warm Amber 2 offers major warm up correction of cool white LED to Tungsten.
Copyright 2023 by David Tamés, some rights reserved. Licensed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. Copyrighted materials incorporated herein are cited or acknowledged in each slide and are used under fair use guidelines for educational use of copyrighted material. All product and company names are trademarks or registered trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.