Sanjay's Lighting Guide

Home  /  Sanjay’s Lighting Guide

sanjayHere I will present all the spectral and performance data for all the LED & Metal Halide lamps I have tested since 1998. The data has been available in my articles published in reef keeping magazines. This is my attempt to make the data more accessible to reef hobbyists all over the world, in a more dynamic format that allows for easy retrieval and flexibility in comparing the performance and spectral data for different lamps. May the Light be with You and Your Reef. – Sanjay Joshi Note: In most cases the data is based on 1 sample lamp and ballast, and some variation should be expected between lamps and ballasts of the same brand and type. For technical issues, please contact admin@reefs.com

What is this site all about?
Over the last several years I have been testing metal halide lamps and ballast combinations in an effort to get some quantitative data on the light output from these lamps and ballasts. The emphasis is not on determining what is the best lamp, but rather to determine what the lamps are actually doing. Once this is known, then we can begin to answer the following questions: Given a bulb/ballast/reflector combination – What light levels and distribution can I expect ?
What are the differences between different bulb/ballast/reflector combinations ?
Does a particular combination meet my needs (coral needs)?
How I can design around the limitations/ strengths of a particular combo?
The site currently does not have data on the reflectors, but this information will be added in the near future. What data is available on this site?
This website has the following data available for over 900 metal halide lamps and ballast combinations:
Plot
The spectral plot shows the amount of power output by a given lamp at different wavelengths. The X-axis shows the wavelength and the Y axis shows the power density. For example, from the spectral plot above, we can see that the Ushio 400W lamp running on a Magnetek ballast has 0.40 Watts/m^2 of power density at 420 nm. Performance data for the lamps and ballast, which includes the power consumption, PPFD, CCT, and efficiency. Lamp name – Identifier used for the lamps (brand name – Wattage – Color Temp as sold – Type of lamp, single ended (SE) or double ended (DE) – Designator for the number of lamp tested, so 1 means sample #1, a 2 would mean sample #2, etc. Ballast name – Ballast used to test the lamp
Shield – (N or Y), indicating if the lamp was shielded with a glass shield when the data was collected. Double ended lamps are usually required to be used with a shield, so data was collected under both shielded and non shielded conditions. PPFD – Photosynthetic Photon Flux Density as measured. see 4 below CCT – Correltated Color temperature, as measured. see 5 below Power – Indicates the actual power consumed in Watts when the lamp was running as measured by a true RMS Watt meter. This is what your electric company will charge you for if you were to use this ballast and lamp combination. Volts – measured the actual volts going into the ballast when the test was conducted Amps – measured the actual amps going into the ballast when the test was conducted. This number can be used to estimate how much amps your wiring will be subjected to under steady state conditions. Remember that this number can be higher when the lamp is starting up. Efficiency – this is ratio of light output to input power (PPFD/Power). Provides an indication at how efficiently power is converted to light. How does the wavelength correspond to color?
The visible light spans the wavelengths from 400 nm to 700 nm. Visually this approximately corresponds to the following colors: 

Violet – 400 to 440nm
Blue – 440 to 490nm
Green – 490 to 540nm
Yellow – 540 to 590nm
Orange – 600 to 650nm
Red – 650 to 700nm

What is PPFD?
PPFD stands for Photosynthetic Photon Flux Density, and is the technically correct term when PAR (Photosynthetically Available Radiation) is measured as the number of photons of light falling on a given area in a given amount of time.. The units are micromoles per meter square per second. 1 micro mole is = 6.023X1017. So for example, when you see a value for PPFD=200 it means that there are 200X6.023X1017 photons falling on a 1 meter square area in one second. What is difference between PAR and PPFD?
PAR is the Photsynthetically Available Radiation which is all radiation between 400-700 nm wavelength range. It can be measured in several units. Just like distance can be measured in feet, meters, etc. PAR can be measured in different units used to measure radiation. When PAR is measured by the number of photons falling on a given area in a given amount of time, this is called PPFD and the units used are micromoles per meter square per second. What is CCT?
Correlated Color Temperature (CCT) which is defined as the value of the temperature of the black body radiator when the radiator color matches that of the light source. So when you see a lamp labeled as 10,000K what it implies is that the color produced by the lamp is similar to color produced by a black body heated to 10,000 Kelvin. Why are these numbers different from what I have seen from other people’s data?
The PPFD measured is a function of the distance at which the data is collected. To compare 2 different readings you have to make sure that the distance at which the measurements are made is the same. Since PPFD measures light falling on a given area, as we increase the distance from the source to the measurement plane, the same amount of photons get spread over a larger area.At what distance are these measurements made?
All measurements are made at 18” from the centerline of the lamp to the top of the sensor dome. What instrument is used to make these measurements?
Licor Spectroradiometer LI-800 Where can I go to get more information?
The following articles from my Facts of Light series provide more detailed information on lighting for aquarium hobbyists. Part I: What is Light?

Facts of Light – Part I: What is Light? by Sanjay Joshi – Reefkeeping.com

The choice of lighting is one the most important decisions to make when setting up a reef tank. The light fixtures and related equipment are some of the more expensive pieces of equipment both at initial setup up as well as in their contribution to daily operating costs.

Part II: Photons

Facts of Light – Part 2: Photons by Sanjay Joshi – Reefkeeping.com

As discussed in Part I, we need to think of light in terms of photons. A photon is the smallest discrete particle of energy that travels along a wave defined by its wavelength, and the amount of energy contained in the photon can be mathematically determined.


Part III: Making Sense of Light Measures

Facts of Light – Part 3: Making Sense of Light Measures by Sanjay Joshi – Reefkeeping.com

The quantity of light at the source is termed flux, and is measured as “quantity” per unit of time. This is very similar to measuring the flow of a pump in gallons/hr or liters/min. We can think of a light source as a pump emitting radiation and measure this pumping capacity over time.


Part IV: Color Temperature

Facts of Light – Part 4: Color Temperature by Sanjay Joshi – Reefkeeping.com

Understanding color temperature starts with understanding black body radiation and the Kelvin temperature scale. A theoretical black body is an object that has no color and is “black” because it absorbs all radiation incident on its surface and emits no radiation at 0° Kelvin.


Part V: Everything You Need to Know About Metal Halide Lamps and Ballasts

Facts of Light – Part 5: Everything You Need to Know About Metal Halide Lamps and Ballasts by Sanjay Joshi – Reefkeeping.com

Metal halide lamps have two basic configurations; those with an outer envelope and those without. In the former, the lamp’s basic construction (see Figure 1) is an inner envelope (called the arc tube), which contains the arc, and an outer envelope (called the bulb) which filters out ultraviolet radiation (UVR) and shields the inner arc tube.

Complete Listing of all of Sanjay’s Reef Related ArticlesSpectral Analysis of MH Lamps  Spectral Analysis of Metal Halide Lamps Used in the Reef Aquarium Hobby Part 1: New 400-watt Lamps, Aquarium Frontiers, Nov 1998. 

Aquarium Frontiers On-Line: Feature

The overall goal is to educate the aquarist about the choices available and to provide some quantitative data with which he or she can evaluate the correctness of the rules of thumb that hobbyists currently use. This article does not suggest which lighting choices are best for reef aquaria, but rather it provides objective data about the lamps that hobbyists currently use.

 Spectral Analysis of Metal Halide Lamps Used in the Reef Aquarium Hobby Part II: Used 400-watt Lamps, Aquarium Frontiers, Jan 1999. 

Aquarium Frontiers Feature

Our initial goal was to track the changes of the same lamps over a period of time, in order to get an idea of how the spectral distribution changes over time.

 Spectral Analysis of Metal Halide Lamps Used in the Reef Aquarium Hobby Part III: New and used 250-watt Lamp, Aquarium Frontiers. 

Aquarium Frontiers On-Line: Feature

The double-ended HQI lamp is very different from the other lamps tested. It is double ended, while all the others have a single screw-type base. It lacks the outer ultraviolet (UV) filtering glass bulb of the other lamps. This lamp must be used in an enclosed fixture with an UV protective shield.

 Joshi, S. and Morgan D., 2001. “Spectral Analysis of Metal Halide Lamps – Do Ballasts Make a Difference,” 2001 Annual Marine Fish and Reef USA , Fancy Publications. Reprint available here  Joshi, S. 2002, “Spectral Analysis of Recent Metal Halide Lamps: Part IV- 10000K and 12000K lamps,” 2002 Annual Marine Fish and Reef USA , Fancy Publications. Joshi, S. and Marks, Timothy. 2002. Spectral Analysis of Recent Metal Halide Lamps and Ballasts, Advanced Aquarist , Oct 2002 , Joshi, S. and Marks, Timothy. 2002. Spectral Analysis of 150W Double Ended Metal Halide Lamps and Ballasts, Advanced Aquarist , Nov 2002 Joshi, S. and Marks, Timothy, 2004. Spectral Analysis of 400W Lamps: XM, Radiums, Osram, Sunmaster and PFO, Advanced Aquarist , Feb 2004 Joshi, S. and Marks, Timothy, 2004. Spectral Analysis of 250W Double Ended Lamps and Ballasts, Advanced Aquarist , Feb 2004 Joshi, S. More Spectral Analysis of 150W Double Ended Lamps, Advanced Aquarist , May 2004. Joshi, S. Spectral Analysis of 250W Mogul Lamps – Part I, Advanced Aquarist , July 2004 Joshi, S. Spectral Analysis of 250W Mogul Lamps – Part II, Advanced Aquarist , Aug. 2004.Joshi, S. More Spectral Analysis of 250W Double Ended Lamps and Ballasts, Advanced Aquarist, Oct. 2004Joshi, S. Spectral Analysis of 400W Double Ended Lamps, Advanced Aquarist, Oct. 2004.Joshi, S. More Spectral Analysis of 400W Lamps and Ballasts: EVC, Hamilton, Aquaconnect and Helios Lamps and EVC, Blueline, Reef Fanatic and Icecap Ballasts, Advanced Aquarist, Jan. 2005.Joshi S. Spectral Analysis of 250 Watt Double Ended Metal Halide Lamps and Ballasts – EVC, Happy Reefing, IceCap, AB, and CoralVue, Advanced Aquarist, Feb. 2005.Joshi, S. Spectral Analysis of 250W Mogul Base Lamps – Part III: EVC, Happy Reefing, Agromax and Coralvue, Advanced Aquarist, April 2005. Joshi, S. Spectral Analysis of Mogul Base Coralvue and Coralvue Reeflux Metal Halide Lamps. Advanced Aquarist, May. 2005Reflector Analysis Joshi, S. and Marks, Timothy, 2003. Analyzing Reflectors: Part 1 – Mogul Reflectors, Advanced Aquarist, March 2003 Joshi, S. and Marks, Timothy, 2003. Analyzing Reflectors: Part II – Double Ended Lamp Reflectors, Advanced Aquarist, July 2003. Joshi, S. and Marks, Timothy, 2004. Analyzing Reflectors: Part III, Advanced Aquarist, March 2004.Joshi, S. 2004. Analyzing Reflectors: 400W DE Reflectors, Advanced Aquarist, Dec. 2004.DIY Articles DIY Calcium Reactor DIY Compact Flourescent DIY MH Lighting System (1999) Others Photosynthesis and Photoadaptation Featured Aquarium in AF Feeding a Reef Aquarium (2000) Exploring the Inner Beauty of Corals, Advanced Aquarist, July. 2002 Penn State Aquarium – Featured Aquaruim in Advanced Aquarist (Oct 2002)