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LEDS 101

LEDS 101

 

This page contains general information about LEDS to help demystify the jargon. 

BEAM aka Optic angle, important for depth penetration
LUMENS A measure of light as seen by the human eye, NOT an important spec in lighting systems because a bright light with high lumens does not necessarily mean a bright light for plants and corals.
PAR aka Photosynthetically Active Radiation, a more important spec in lighting systems than lumens, a measure of light that your plants and corals receive
SPECTRUM aka light wavelength, an important spec because plants and corals require specific wavelengths of light to survive.
KELVIN a measure of the overall colour of a lighting system as perceived by the human eye. Contrary to popular belief, KELVIN is NOT an important specs for plant and coral growth, it is a measure of what looks good to you.
CRI a measure of how natural the light looks compared to sunlight, commonly specified as a number for 1 to 100, 100 being exactly like daylight. NOT an important spec for plant and coral growth but important for visual aesthetics.

 

 BEAM ANGLE (aka OPTIC ANGLE)

MakeMyLed have four beam angles (aka optic angle), 120°, 90°, 60° and 45°,  to deliver the right amount of light for the width and depth of your aquarium.

The way beam angles work is simple, the wider the beam angle the more surface area coverage you get and the less depth penetration you get, the narrower the beam angle the less surface area coverage you get and the more depth penetration you get so it's simply a matter of choosing a beam angle that suits the height of your tank.

Use the chart below to work out what beam angle suits your tank. For height, measure the distance from the top of your substrate (soil/gravel) to the top of your tank and add 7cm for the distance from the top of your tank to the light fixture. If you plant to suspend the fixture above the tank or to the underside of a hood make sure you include that distance in your calculation.    

beam-angle.jpg  

 PAR (aka Photosynthetically Active Radiation)

You've probably heard of LUMENS , PAR (Photosynthetically Active Radiation) and PPFD (Photosynthetic Photon Flux Density) as a measure of brightness, put simply LUMENS is brightness as perceived by the human eye and PPFD is brightness as perceived by your tank inhabitants and varies according to the depth of your tank and the condition of your water.

A light that looks bright to you has high LUMENS but doesn't necessarily make it a good light for your aquarium. PPFD (aka PAR) is the measure of the amount of light that falls on objects in your tank e.g. plants and corals. PPFD is measured by a PAR/PPFD Meter (AKA Quantum Meter) and is a measure of the number of light photons that reach a target over a square metre every second, commonly measured in units called μmol/m2/s (micromoles per square meter per second)

PAR readings vary with depth and are also affected by the clarity of aquarium water, the deeper you go the lower the PAR reading will be so you can see that PAR readings at specific depths are very useful measurements of how much light your plants and corals actually get at those depths and is scientic way to evaluate light performance.

LED fixture manufacturers and resellers who don't publish PAR readings for their lights either don't know what the readings are or they have such poor PAR performance that they don't want to disclose this. As a general rule if you don't see PAR readings for the light you are cnsidering buying then steer clear or you may end up wasting your $ on something that won't do the job.

MakeMyLed publish PAR readings for all of their light fixtures as measured by LAB grade quantum meters in real conditions so can make an informed choice and know exactly what you'll be getting.

 SPECTRUM (aka light wavelength)

We've seen that PPFD/PAR is a measure of how much light falls on Plants or Corals in your aquarium, Spectrum is the measure of how useful that light is for Plants and Corals.

Spectrum is measured as a wavelength in nanometers (nm) and certain wavelengths are more beneficial for plants and corals and other wavelengths are less benefcial. So it's not only PAR that is important,Spectrum is equally if not more important.

Both plants and corals use light to go through a process called photosynthesis in which light energy is converted to chemical energy which in turn is used to fuel the organism's activities. Plants photosynthesise light to grow and zooxanthellae algae in Coral polyps do the same.

The diagram below shows the photosynthesis peaks (aka Chlorophyll peaks) that are important for both plants and zooxanthellae algae in Corals.

grow-absorbtion-peaks.jpg

 

You can see from the diagram that the Chlorophyll-B has two wavelength peaks, one at just under 450nm and the other at 660nm, Chlorophyll-A also has two wavelength peaks, one at around 470nm and the other at 620nm.

As a general rule, Plants and Corals need light containing at least one Chlorophyll-A peak and one Chlorophyll-B peak to thrive so LED light fixtures must meet this requirement to be of any use.

Again the general rule is that if LED manufacturers don't quote the light wavelength then this should ring alarm bells and you should steer clear from buying these.

MakeMyLed quote both PAR and Spectral wavelengths for all of their LED systems.

 KELVIN TEMPERATURE (aka K Rating)

This is a very misunderstood measurement of light. KELVIN TEMPERATURE (aka KELVIN RATING or KELVIN COLOUR) refers to the colour of light as perceived by the human eye. Low KELVIN readings have more red in the overall colour and high KELVIN readings have more blue in the overall colour. KELVIN is not an important measurement for for plants and corals but it is important for aesthetic reasons because you're the one that will be looking at the aquarium.

kelvin.jpg

6500K to 1000K is a pleasant colour to look at for fresh water tanks, 12000K and higher is a pleasant colour to look at for marine tanks.

 CRI (aka Colour Rendering Index)

This is a percentage from 1% to 100% representing how accurately the light will reproduce natural colours in your aquarium, the higher value being the better. This is also not important for the health and wellbeing of plants and corals and high numbers are purely sought for aesthetic reasons.

 

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