COLOR

  • Types of Film Lights and their efficiency – CRI, Color Temperature and Luminous Efficacy

    nofilmschool.com/types-of-film-lights

     

    “Not every light performs the same way. Lights and lighting are tricky to handle. You have to plan for every circumstance. But the good news is, lighting can be adjusted. Let’s look at different factors that affect lighting in every scene you shoot. ”

    Use CRI, Luminous Efficacy and color temperature controls to match your needs.

     

    Color Temperature
    Color temperature describes the “color” of white light by a light source radiated by a perfect black body at a given temperature measured in degrees Kelvin

     

    https://www.pixelsham.com/2019/10/18/color-temperature/

     

    CRI
    “The Color Rendering Index is a measurement of how faithfully a light source reveals the colors of whatever it illuminates, it describes the ability of a light source to reveal the color of an object, as compared to the color a natural light source would provide. The highest possible CRI is 100. A CRI of 100 generally refers to a perfect black body, like a tungsten light source or the sun. ”

     

    https://www.studiobinder.com/blog/what-is-color-rendering-index/

     

     

     

    https://en.wikipedia.org/wiki/Color_rendering_index

     

    Light source CCT (K) CRI
    Low-pressure sodium (LPS/SOX) 1800 −44
    Clear mercury-vapor 6410 17
    High-pressure sodium (HPS/SON) 2100 24
    Coated mercury-vapor 3600 49
    Halophosphate warm-white fluorescent 2940 51
    Halophosphate cool-white fluorescent 4230 64
    Tri-phosphor warm-white fluorescent 2940 73
    Halophosphate cool-daylight fluorescent 6430 76
    “White” SON 2700 82
    Standard LED Lamp 2700–5000 83
    Quartz metal halide 4200 85
    Tri-phosphor cool-white fluorescent 4080 89
    High-CRI LED lamp (blue LED) 2700–5000 95
    Ceramic discharge metal-halide lamp 5400 96
    Ultra-high-CRI LED lamp (violet LED) 2700–5000 99
    Incandescent/halogen bulb 3200 100

     

    Luminous Efficacy
    Luminous efficacy is a measure of how well a light source produces visible light, watts out versus watts in, measured in lumens per watt. In other words it is a measurement that indicates the ability of a light source to emit visible light using a given amount of power. It is a ratio of the visible energy to the power that goes into the bulb.

     

    FILM LIGHT TYPES

    https://www.studiobinder.com/blog/video-lighting-kits/?utm_campaign=Weekly_Newsletter&utm_medium=email&utm_source=sendgrid&utm_term=production-lighting&utm_content=production-lighting

     

     

     

    Consumer light types

     

    https://www.researchgate.net/figure/Emission-spectra-of-different-light-sources-a-incandescent-tungsten-light-bulb-b_fig1_312320039

     

    http://dev.informationdisplay.org/IDArchive/2015/NovemberDecember/FrontlineTechnologyCandleLikeEmission.aspx

     

     

    Tungsten Lights
    Light interiors and match domestic places or office locations. Daylight.

    Advantages of Tungsten Lights
    Almost perfect color rendition
    Low cost
    Does not use mercury like CFLs (fluorescent) or mercury vapor lights
    Better color temperature than standard tungsten
    Longer life than a conventional incandescent
    Instant on to full brightness, no warm-up time, and it is dimmable

    Disadvantages of Tungsten Lights
    Extremely hot
    High power requirement
    The lamp is sensitive to oils and cannot be touched
    The bulb is capable of blowing and sending hot glass shards outward. A screen or layer of glass on the outside of the lamp can protect users.

     

     

    Hydrargyrum medium-arc iodide lights
    HMI’s are used when high output is required. They are also used to recreate sun shining through windows or to fake additional sun while shooting exteriors. HMIs can light huge areas at once.

    Advantages of HMI lights
    High light output
    Higher efficiency
    High color temperature

    Disadvantages of HMI lights:
    High cost
    High power requirement
    Dims only to about 50%
    the color temperature increases with dimming
    HMI bulbs will explode is dropped and release toxic chemicals

     

     

    Fluorescent
    Fluorescent film lighting is achieved by laying multiple tubes next to each other, combining as many as you want for the desired brightness. The good news is you can choose your bulbs to either be warm or cool depending on the scenario you’re shooting. You want to get these bulbs close to the subject because they’re not great at opening up spaces. Fluorescent lighting is used to light interiors and is more compact and cooler than tungsten or HMI lighting.

    Advantages of Fluorescent lights
    High efficiency
    Low power requirement
    Low cost
    Long lamp life
    Cool
    Capable of soft even lighting over a large area
    Lightweight

    Disadvantages of Fluorescent lights
    Flicker
    High CRI
    Domestic tubes have low CRI & poor color rendition.

     

     

    LED
    LED’s are more and more common on film sets. You can use batteries to power them. That makes them portable and sleek – no messy cabled needed. You can rig your own panels of LED lights to fit any space necessary as well. LED’s can also power Fresnel style lamp heads such as the Arri L-series.

    Advantages of LED light
    Soft, even lighting
    Pure light without UV-artifacts
    High efficiency
    Low power consumption, can be battery powered
    Excellent dimming by means of pulse width modulation control
    Long lifespan
    Environmentally friendly
    Insensitive to shock
    No risk of explosion

    Disadvantages of LED light
    High cost.
    LED’s are currently still expensive for their total light output

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  • Polarised vs unpolarized filtering

    A light wave that is vibrating in more than one plane is referred to as unpolarized light. … Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization.

    en.wikipedia.org/wiki/Polarizing_filter_(photography)

     

    Light reflected from a non-metallic surface becomes polarized; this effect is maximum at Brewster’s angle, about 56° from the vertical for common glass.

     

    A polarizer rotated to pass only light polarized in the direction perpendicular to the reflected light will absorb much of it. This absorption allows glare reflected from, for example, a body of water or a road to be reduced. Reflections from shiny surfaces (e.g. vegetation, sweaty skin, water surfaces, glass) are also reduced. This allows the natural color and detail of what is beneath to come through. Reflections from a window into a dark interior can be much reduced, allowing it to be seen through. (The same effects are available for vision by using polarizing sunglasses.)

     

    www.physicsclassroom.com/class/light/u12l1e.cfm

     

    Some of the light coming from the sky is polarized (bees use this phenomenon for navigation). The electrons in the air molecules cause a scattering of sunlight in all directions. This explains why the sky is not dark during the day. But when looked at from the sides, the light emitted from a specific electron is totally polarized.[3] Hence, a picture taken in a direction at 90 degrees from the sun can take advantage of this polarization. Use of a polarizing filter, in the correct direction, will filter out the polarized component of skylight, darkening the sky; the landscape below it, and clouds, will be less affected, giving a photograph with a darker and more dramatic sky, and emphasizing the clouds.

     

    There are two types of polarizing filters readily available, linear and “circular”, which have exactly the same effect photographically. But the metering and auto-focus sensors in certain cameras, including virtually all auto-focus SLRs, will not work properly with linear polarizers because the beam splitters used to split off the light for focusing and metering are polarization-dependent.

     

    Polarizing filters reduce the light passed through to the film or sensor by about one to three stops (2–8×) depending on how much of the light is polarized at the filter angle selected. Auto-exposure cameras will adjust for this by widening the aperture, lengthening the time the shutter is open, and/or increasing the ASA/ISO speed of the camera.

     

    www.adorama.com/alc/nd-filter-vs-polarizer-what%25e2%2580%2599s-the-difference

     

    Neutral Density (ND) filters help control image exposure by reducing the light that enters the camera so that you can have more control of your depth of field and shutter speed. Polarizers or polarizing filters work in a similar way, but the difference is that they selectively let light waves of a certain polarization pass through. This effect helps create more vivid colors in an image, as well as manage glare and reflections from water surfaces. Both are regarded as some of the best filters for landscape and travel photography as they reduce the dynamic range in high-contrast images, thus enabling photographers to capture more realistic and dramatic sceneries.

     

    shopfelixgray.com/blog/polarized-vs-non-polarized-sunglasses/

     

    www.eyebuydirect.com/blog/difference-polarized-nonpolarized-sunglasses/

     

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  • Photography basics: Color Temperature and White Balance

     

     

    Color Temperature of a light source describes the spectrum of light which is radiated from a theoretical “blackbody” (an ideal physical body that absorbs all radiation and incident light – neither reflecting it nor allowing it to pass through) with a given surface temperature.

    https://en.wikipedia.org/wiki/Color_temperature

     

    Or. Most simply it is a method of describing the color characteristics of light through a numerical value that corresponds to the color emitted by a light source, measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000.

     

    More accurately. The color temperature of a light source is the temperature of an ideal backbody that radiates light of comparable hue to that of the light source.

    As such, the color temperature of a light source is a numerical measurement of its color appearance. It is based on the principle that any object will emit light if it is heated to a high enough temperature, and that the color of that light will shift in a predictable manner as the temperature is increased. The system is based on the color changes of a theoretical “blackbody radiator” as it is heated from a cold black to a white hot state.

     

    So, why do we measure the hue of the light as a “temperature”? This was started in the late 1800s, when the British physicist William Kelvin heated a block of carbon. It glowed in the heat, producing a range of different colors at different temperatures. The black cube first produced a dim red light, increasing to a brighter yellow as the temperature went up, and eventually produced a bright blue-white glow at the highest temperatures. In his honor, Color Temperatures are measured in degrees Kelvin, which are a variation on Centigrade degrees. Instead of starting at the temperature water freezes, the Kelvin scale starts at “absolute zero,” which is -273 Centigrade.

     

    More about black bodies here: https://www.pixelsham.com/2013/03/14/black-body-color

     

     

    Details in the post

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LIGHTING