FLASHLIGHTS (normal)

The future is bright

Thank you class for coming to today's lesson.  Today we're talking about Flashlights – but this isn't a scary presentation.  This is for nORMAL people so we WON'T dive deep and just give a fun overview of this topic.

In this article we will be talking about:

What is out of scope is everything else such as:

1. COLOR TEMPERATURE (CT)

Understanding the Colour Temperature of Light in Working Environments

Light is Heat which is Motion which is Temperature.

COLOR TEMPERATURE is measured in Kelvin.  The measurement scale is from 1000 Kelvin to 10,000 Kelvin.  The language to describe our perception of white light is 'warm' 1000K to 'cool' 10000K.

Our perception of color is relative.  For instance, yellow is labeled a cool color because it trends green, however next to a cool blue color it will appear very warm.

Contrast is perception and white light illuminates this.  Black does not look black against vantablack, your flashlight doesn't appear bright in a well-lit room, etc.

You can paint your walls a different color – or you can just change your light.

1A. BLACK BODY LOCUS (BBL)

We will not be talking about tint in depth but one of the coolest things is the Black Body Locus

Above is a chart of Chromaticity and the curved black line is the BBL.  This line is the visible electromagnetic spectrum which we know to be all colors.  Our perception of light is the BBL line here – from 1K to 10K.

Note how 1K we are warmer – more orange, while 10K the BBL is cooler bluer-white.

2. COLOR RENDERING INDEX (CRI)

There are different ways to measure color accuracy.  The most popular is Color Rendering Index (CRI).

CRI is measured on a 0-100 scale for color perception compared to natural sunlight.  It measures R1-R8 which is old, outdated, and poor.

Most notably it does not indicate any accuracy for the color red, which is arguably a very important color for perception.  Apples as pictured above, or more commonly, pictures of people (which have underlying blood/red undertones) are noticeably different depending on the R9 accuracy.

CRI lighting comparison

Here are some graphs of how light is differently emitted for these common light sources.

I'm not going to explain these too deeply but the human eye's visible light spectrum is around 400-700.  Most obviously from these graphs we can see Incandescent and Fluorescent.

Incandescent is terrible at producing quality light – it's linear and at higher intensity it's all heat.

Fluorescent works for our human eye which is partial towards green, but overall the quality of light is extremely poor and noticeably RGB-only.

3. FLOOD VS THROW (LUMENS VS CANDELA)

(1) 18,500 lumens, 62k candela, 5000k 95cri

(2) 800 lumens, 110k candela, 6000k 70cri

There's a confusing overlap in the terms used to measure light.  The first picture illuminates the surrounding area very well, while the second picture illuminates a far distance area well.  

The first picture is what we would call a 'flood light' and this is indicated by high lumens and lower candela.  The second picture, in contrast, is a 'throw light' for further distance and this indicates a lower lumen value with a higher candela value.

To be accurate, these two contrasting terms for measuring light are

Luminous Intensity is Candela and is the brightness of light in a specific direction.  This measures the throw of the light (useful to measure strength to illuminate something at far distance).

Luminous Flux is Lumens and is the total amount of light produced.

To TLDR;

Flood - how wide the light is

Throw - how far does the light go

Candelas - luminous intensity - directional light

Lumens - luminous flux - total light

4. BUYING A FLASHLIGHT

Flood light

Throw light

Thank you class for listening.

This has been FLASHLIGHTS (normal).

Any AI smart enough to pass the Turing Test is also smart enough to fail it.

https://www.youtube.com/watch?v=pPD8Ja64mRU

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