Lumens: What You Need to Know
What is a lumen?
A lumen is a measurement of light. It tells you exactly the amount of light you should expect your chosen light bulb to produce. In more technical terms, a lumen is a finite measurement of how much visible light is emitted by a source and which can be detected by the human eye. Lumens are increasingly being used on the packaging of bulbs in an attempt to help consumers make more informed choices. In some countries these changes are necessary by law. Knowing what a lumen is will help people choose a light bulb which is right for their needs.
What about Watts?
It is true that the light bulb industry has traditionally printed watt ratings on their product packaging rather than lumens, but with energy saving bulbs on the market, you should find lumens listed more and more on newer packaging. This will help you understand how much light output a bulb will produce, with newer bulbs not using the same Watts as traditional incandescent bulbs.
Many people still often think in terms of Watts for the amount of light a bulb will produce. For that reason, here is a handy little conversion list for you to roughly gauge which lumen rating to use against common watt outputs:
- For an incandescent 100 watt bulb, try replacing it with a bulb of around 1600 lumens.
- For a 75 Watt bulb, around 1100 - 1200 lumens should suffice.
- For a 60 Watt bulb, try a bulb of between 700 - 900 lumens
- For a 40 Watt bulb, a bulb producing between 400 - 500 lumens should be perfect.
Understanding lumen output, on it's own, or in relation to traditional incandescent Wattage ratings, will help you make the right choices in selecting light bulbs for use in each room in your home or office.
CRI simplified: What it is and why it is important
CRI stands for Color Rendering Index. Broadly speaking, it is a measurement of a light source's appearance when used to illuminate an object. In other words:
- How close to "naturally" lit does the object appear?
- Do all the colors of object display to the same level?
- What kind of natural light does it most closely resemble? Night or Day? Overcast or bright?
In essence, the CRI of a light source tells professionals and enthusiasts alike what an environment will look like when illuminated by a specific light.
How does it work?
CRI is used to rate how well a light source illuminates colors in comparison to an incandescent light, or in daylight. The highest rating a light source can be given is 100. If a light is rated at 100 CRI, then that simply means that the light source illuminates the color of objects just as well as natural, daytime sunshine in the best possible condition. Each color will appear as well lit as any other. If a light source is rated at 50 CRI, then it would illuminate some or all or the colors of objects at roughly half the quality of daytime sunshine or an incandescent bulb.
An incandescent bulb has a CRI rating of around 95, which means that it is very close to illuminating all colors of objects to a similar level. On the other hand, have you ever been somewhere and noticed that everything looks horribly cold and almost washed out? Usually this will be in an office building or warehouse. This is normally due to the light source in these environments being fluorescent bulbs with a CRI rating of around 60. The bulbs may be bright and help you see everything clearly, but the colors of the environment look too similar and faded.
What complicates things further is CCT, which is often mistaken for CRI.
CCT stands for Correlated Color Temperature and tells you the color of light produced by a white light source. This might sound strange, "the color of white light?" Yes, you read that right. White light is produced by every color being present–all the colors of the rainbow–but in some cases one color might be a little more dominant than another. The CCT of a light source tells you which colors are more dominant. This is measured in Kelvin. For example, a light source with a CCT of K2500 is going to appear redder or "warmer" than a bluer or "colder" K6500 bulb. So CCT tells you the color of the white light, and the CRI tells you how uniformly colors of objects will appear when illuminated.
CRI isn't about the color of the light, it's about how natural object colors appear.
Who uses it?
Photographers, videographers and lighting technicians all use CRI to make decisions about what lighting to use for the best color appearance in photo, video, or on stage. Only through knowing about light sources, CRI, and CCT can these professionals truly control and produce the quality in lighting that they desire.
It isn't all about an image or the stage, though. CRI can come in useful home design as well. You might want to use a different type of light source for certain rooms in your house or apartment, creating a specific atmosphere, without sacrificing the quality of the light you use.
CRI is only a complicated subject if you let it be. Hopefully this information has simplified it for you and will act as a foundation for you to learn even more in the future. Whether it is for your home, your hobby, or your profession, go out there and put this knowledge into practice. Make the world look great!