Flashlight School, a Transcription:

The Video; Things you need to know before buying a Flashlight – The importance of Lumens, Lux, and Candela; which Follows, and is Interesting to Watch, has arduously been Transcribed by me, so that one can reflect on the Items Mentioned.

Please bear in Mind that many Flashlights are not Toys, and Careless Use can result in Human and Animal Eye Damage from Flashlights and Headlamps with High Outputs and some that may have a lower output, relatively speaking. I had looked at a certain Model LED Headlamp, at a Close Distance, when it unexpectedly came on, and had a Green Circle in my Retina for hours afterwards, and this Headlamp was not by any means known as really bright. LEDs have a Phenomenon known as Point Source, the Intense LED Light is produced at an Electrical Junction, a very Tiny Point, rather than being Distributed Over an Incandescent Filament, this Intense Point of Light can Cause Harm from a variety of LED Products.

The Ultraviolet Flashlight I describe below, this is not a Toy, this is Insanely Bright for a U.V. Light and I would imagine Damage to Human and Animal Eyes could occur with Careless Use.

Effects of White Light‐Emitting Diode (LED) exposure on Retinal Pigment Epithelium 

High Output Flashlights Can Start Fires. Use Care in Use and in Delegating Responsibility to whom is permitted to use them.  Crazy Russian Hacker (a YouTube Channel) offers some significant cautions about High Power Flashlights that are missing in the otherwise excellent show I transcribed.

Flashlight Fire Starter

Can You Start a Fire With LED Flashlight?

Things you need to know before buying a Flashlight – The importance of Lumens, Lux, and Candela

Luminous Flux measured in Lumens is the Total Light Output of a Light, often listed first in Specifications of a Flashlight.

The Reflector, and sometimes a Lens, Focuses and Directs the Light in a certain way, such as a Flood Light or a Beam. This relates to the Intensity of the Light, Intensity in a Particular Direction is referred to as Luminous Intensity, and is measured in Candela aka Candle Power.

Below is an Additional Definition of the Word, such Additions and Comments that were not in the Original Video will be Contained Within Horizontal Lines. 

National Institute of Standards and Technology – NIST
Candela – Latin Word for Candle

The candela is the SI’s base unit for photometry—the science of measuring light as perceived by the human visual system. It is as notable for what it does not do as for what it does: It does not represent the entire amount of light shining from an object; we have a different unit called the lumen for that. It is not used for every kind of electromagnetic radiation; radio waves, X-rays and other types of light our eyes cannot detect are measured in watts of power. The candela is particular. It measures light we can see, coming directly from a source we can see, straight into our eyes. 

You can have a Lower Power Flashlight, i.e. Less Lumens, which can have Higher Intensity than a Higher Power Flashlight when Direction is considered.

Analogy of Hose with Adjustable Nozzle, same pressure can cover a large area with spray head, or be concentrated into narrow jet to project much further. In other words, a Flood vs Beam light. This is where the Range, i.e. Light Throw, is considered.

Candela Rating is Better than Lumen for a Spotlight or Long Range Light. These (Spotlight and Long Range Lights) are generally best served by a Single LED and Bigger Reflector than Multi-LEDs or Smaller Reflector that are often used for Floodlighting.

LUX is the Amount of Light Hitting a Surface, and that’s Measured with a Light Meter. ANSI FL1 Standard States that the Maximum Range of a Light is a Measure of the Distance from the Light when the Surface Light Level Drops to .25 of a Lux, which is a very low light level, similar to Moonlight.

Lux is a unit of illumination equal to the direct illumination on a surface that is everywhere one meter from a uniform point source of one candle intensity or equal to one lumen per square meter

Flashlight with Range of 500 Meters, don’t expect to spot a black cat at that range with Moon Level Brightness. The Light then must travel back to the eye, and Moisture and Dust will obscure some of it, so some people feel an actual effective range is 1/4 of the stated value. A 500 Meter Light would more realistically be most useful at 125 Meters.

Perception of light is non-linear, and that also influences Flashlight Choice. A Flashlight with Double the Output does not appear Twice as Bright. For a Flashlight to be Twice as Bright it needs to be 4X the Intensity. Buying a Flashlight with a Few More Lumens will not seem to be Significantly Brighter. Rather, Consider Run Time, Candela Rating, Beam Pattern, ease of Operation, etc.

Run Time is also Addressed in ANSI FL1 Standard as the Time Beginning 30 Seconds after the Light is Switched-on Until the Output Reaches 10% of the Original Measurements. Though older technologies showed a Steady Decrease in Brightness Over Time, newer technologies Maintain a Constant Brightness Over Time Except in Very High Brightness Modes, often referred to as Turbo. With these; in the Turbo Mode; the Intensity Drops after a relatively short period of time. This may be due to Circuits Designed to Protect the Flashlight Electronics from Overheating as this can happen at High Brightness Levels. Though the Flashlight may permit the Turbo Mode to be re-engaged once the Flashlight has cooled below a Certain Level, repeated engagements of Turbo Mode will shorten the overall Run Time.

He offered examples of Turbo Mode vs Length of Time until it drops to a Lower Output, and the model he showed also had Time Limits on the Brightness Mode that was the next Step below Turbo.

  • 25,000 Lumens for 70 Seconds Drops to 4,000 Lumens for 1 Hr. 20 Min.
  • 9,000 Lumens for 2 Min. Drops to 4,000 Lumens for 1 Hr. 30 Min.
  • 4,000 Lumens for 2 Hr. 18 Min.
  • 2,500 Lumens for 4 Hr.
  • 1,200 Lumens for 8 Hr.
  • 200 Lumens for 31 Hr.

He also offered examples of the Environment determining the length of time that a Flashlight can Operate in Turbo Mode or High Brightness Modes, saying use in the Arctic may have longer times before the Intensity Drops than Operating it in a Hot Climate, like the Amazon.

In my Opinion, Timers are Less Expensive than Thermostat Measuring Circuits, and it’s likely that at least some will only operate for a Specific Time in Turbo or High Brightness Modes Regardless of the Ambient Temperatures.

I think on Many Flashlights and Headlamps with Regulated Voltage provided to the LED maintain a Constant Brightness until the Available Voltage Drops Below a specific point. Not all are Regulated.

Form Factor will make a Difference in Selection. Do you want a Compact Light, a Hands Free Headlamp, a Spotlight, a Powerful Flood Light, or something Really Compact that will fit in your Pocket for Every Day Carry (EDC). Another Feature is do you want a Firefly (Moonlight) Mode. This Mode is used to not Interfere with others around you, or to use the Light without Recharging (as a Night Light) that can go Weeks if not Months without Recharging the Battery.

With the Exception of some Tactical Lights that have a very Firm Tail Switch to Operate, many Flashlights have a Lock-out Mode to Prevent it from Being Switched on as it is in Storage (Luggage or Backpack) and is being Knocked About. He then suggests if that mode Doesn’t Exist, to Unscrew the Tail End of the Light somewhat to Disable the Flashlight.

I’d suggest storage that prevents movement in such a way that makes an Accidental Switching-on Impossible, such as a Case Designed by the Manufacturer. Crazy Russian Hacker Suggests, in one of the Videos Above, to Replace the Insulator in one model Flashlight he has, while in Storage, to prevent the Light from coming on. He also shows Fires that can be Started by High Intensity Flashlights (and probably some not so High in Intensity as well). 

  • Some Tactical Flashlights have a Strobe Function to Disorientate an Attacker and may be useful.
  • Some Flashlights have a Strobe Beacon, Flashes a Periodic Intense Burst of Light used to Attract Attention.
  • Some Flashlights have an SOS Mode that Flashes SOS in Morse Code, he doesn’t appear to see the benefit of this for most users.
  • Some Flashlights, particularly Headlamps have a Red LED Mode, that works at Different Intensities, and that will operate in Flash Mode. Useful for Moving Around at Night to Preserve your Eyes being Adapted to the Dark, or as a Safety Aid.

Lights may Specify Warm Light or Cool Light, and that relates to the Color Temperature of the Light, Measured in Kelvin. Lights specified near the 4000 Kelvin Range are Warm Colored (More Orange), Lights Specified near 6000 Kelvin are Regarded as a Cooler Light, Blue Light, or Natural Daylight.

He Talks about the Different Light Levels that Flashlights Have, and the use of the Light Switch to Step Through the Various Light Levels.

IPX Rating is How Protected the Flashlight is Against Water Ingress.

  • IPX4 is Splash Proof
  • IPX5 is Water Resistant Against Low Pressure Jets
  • IPX6 is Water Resistant Against High Pressure Jets
  • Everything IPX7 and Above is Classified as Water Proof. IPX7 Can be Submerged to 1 Meter for 30 Minutes
  • IPX8 Can be Submerged to 2 Meters for 30 Minutes.

IP Rating, rather than IPX, Provides Numbers such as IP68. In his Example, the 6 Stands for Dust Proof Abilities, and the 8 Pertains to Water Proof as already described in the IPX Paragraph. He stated that Generally the Water Resistant or Water Proof Abilities are usually the only one stated since if it’s Water Resistant or Water Proof, it’s Dust Proof as well.

Impact Resistance is quoted as a Drop Distance onto Cured Concrete from a specified Distance 6 Times in succession at Different Angles that generally Match the Sides of a Cube, without the Flashlight having Suffered Material Damage or Loss of Function.

  • Rechargeable Batteries have Higher Power Densities than Disposable Batteries, so usually offer more Power for a Longer Period of Time, the Drawback Being that Replacement Batteries are not Conveniently Available in Local Stores if you unexpectedly run out of power, and that is assuming that there are shops around.
  • Bigger Batteries Generally give Longer Run Times, most are usually Lithium Ion but some are Lithium Polymer, though the Polymer are Generally in Flashlights that do not have Replaceable Flashlights.
  • USB-C Charging is Preferable to Micro USB, they are More Reliable, Charge More Quickly, and Correctly Orienting the Plug is not needed.
  • Some Batteries have the Charging Socket Built into the Battery, it’s beneficial since if the Connection becomes Faulty on the Device End, you simply Replace the Battery to Restore the Connection, not the Flashlight, and the Connection is Protected by being Inside the Flashlight and is Less Prone to Water and Dust Ingress.
  • Socket on the Flashlight is More Convenient, Simply Plug in the Charger without Removing the Battery, and in Some Cases, the Flashlights can be Hooked into a Power Back and Used while they are Charging.
  • Some Batteries or Flashlights use a Connector, some have Magnetic Mated Charger Connectors, but can be an issue if the Special Connector becomes Lost or Broken. He prefers Standard USB Connectors as he normally has them anyway.
  • Most Manufacturers don’t supply a Charger, because most people have them to begin with, but the Manufacturer supplies a Charging Lead.

The above is the Transcription of the Show, I have endeavored to keep it accurate but it is, at times, not verbatim. In addition, I cannot fully attest to the topics he addressed, but they seem to be what I would expect.

He Didn’t seem to Mention that Specialized Flashlights are Available. I have an Ultraviolet Flashlight, for Example. Another has U.V. and Green LED’s in addition to White.


In the Photographs Below, the Red Dot in the Upper Right Corner of the Lower 4 Images (Left and Right) is a Laser Pointer used to be sure the Areas I Photographed without and with the U.V. Light were Identical.


In Articles on Flashlights, it’s not Uncommon to see the Terms Spot and Spill. From the Transcription, if I correctly understand, Flood Lights may not have much noticeable difference between the two, but Spotlights would seem likely to Create a Bright Spot and have a duller Spill Area.

Spot and Spill

More of My Blogs on Flashlights:

Christmas 2022 Gift Suggestions, Flashlights, the Perfect Gift!

Christmas 2022 Gift Suggestions, Flashlights, the Perfect Gift!

Bright Flashlights, Spotlight, Particles in Air, and Masks.

Bright Flashlights, Spotlight, Particles in Air, and Masks.

My Headlamp Collection and Warning on Possible Retinal Damage That May Occur from Some LED Products

My Headlamp Collection and Warning on Possible Retinal Damage That May Occur from Some LED Products

Coleman 2D Boosterbeam and Streamlight LED Explosion Proof Flashlight

Coleman 2D Boosterbeam and Streamlight LED Explosion Proof Flashlight

LED Lighting Can Cause Retinal Damage

LED Lighting Can Cause Retinal Damage

Ultraviolet Light and the Things You’d Rather Not See!

Ultraviolet Light and the Things You’d Rather Not See!

Author: Dr-Artaud

A Doctor that is not a Doctor, but named after a character in the movie "No Such Thing", as is the Avatar.

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