A foot candle is a unit of measure for light intensity in an area. It measures the brightness of the space being illuminated instead of taking measurements at the source. One foot-candle is equal to one lumen of illumination per square foot, measured at a foot from the light source. But how can you know it?
What is actually a foot candle?
As we have already mentioned, it is a unit of measurement that gauges the amount of light that is cast on a given surface. One foot-candle is approximately equal to the light produced by one candle burning at a distance of one foot. The name “foot-candle” is derived from the Latin words candela and pedes, which mean “candle” and “foot,” respectively. Foot candles are typically used to measure the brightness of an area in terms of how much light is available for people to see. In other words, it’s a way to determine how well-lit an area is. The brighter the area, the more foot candles it will have.
A candlepower (abbreviated as Pd) is a unit of illumination that measures the brightness of light over a given area. The one-foot candle is the equivalent of one lumen of light covering one square foot from a distance of one foot away. A lux, in contrast, is the same measurement but instead refers to light in square meters rather than feet. If you ever have to compare them, recall that 10.76 lux equals 1 foot-candle.
This means that if you were to take a light source and place it one foot away from a one-square-foot area, that light would be considered one foot-candle. If you placed it two feet away, it would be half as bright, or 0.5 foot-candles. The further away the light is, the lower the foot-candle reading will be.
Now that we know how to calculate foot candles, let’s discuss how this unit of measure can be used in different lighting applications.
So, how to measure foot candles?
You can measure foot candles with a light meter. A light meter is a device that measures the intensity of light in a given area. It’s commonly used in photography to determine the proper exposure for a photo, but it can also be used to measure the amount of light in an area. To use a light meter to measure foot candles, you will need to take a reading from the light meter and then multiply it by 10.76. This will give you the number of foot candles in the area that you are measuring.
It is possible to use a light meter to measure foot candles. Simply position the meter on the surface you wish to measure and it will provide a reading. Keep it close to the surface; it'll be off. You should use a light meter on the most important surface in any given area. So, in your office or dining room, you'll want to take measurements of the light on the desk or table. If you're doing this for a home theater, the media cabinet or screen would be the best surface to measure.
A light meter can also give you an average foot candle reading for an entire room. To do this, simply take readings in different areas of the room and then average them out. This will give you a good idea of the overall light level in the space.
How do you calculate foot-candles?
To figure out how many lumens you'll need, multiply your room's square footage by its foot-candle requirement. For example, a living room with 100 square feet needs 10-20 foot candles, whereas a dining area with the same amount of space requires 3,000-4,000 lumens.
So, for calculating foot candles, you need to know the square footage of the area and the foot-candle requirement for that particular space. Once you have those two numbers, simply multiply them together to calculate the number of lumens required for the space.
What does 1 foot-candles look like?
If you are eager to know what 1 foot-candle looks like, you can easily calculate it. For this, you need to know the area of your room in square footage. Once you know that, simply multiply the square footage by 0.002928 to get the number of luxes required for 1 foot-candle. For example, if your room is 200 square feet, then you need 585.6 luxes for 1 foot-candle. However, if your room is smaller or larger, the number of luxes required will change accordingly.
A 1-foot candle looks like a small spot of light on a wall or other surface. The size of the spot will depend on the distance from the light source. At one foot away, the diameter of the spot will be 1/2 inch. At two feet away, the diameter of the spot will be 1 inch. At three feet away, the diameter of the spot will be 1-1/2 inches.
The further away you are from the light source, the larger the spot of light will be.
How many foot candles should I read?
In offices, general areas should be illuminated with 20-foot candles. In places where reading and detailed work is done, 50-foot candles of light are sufficient. Conference rooms and other spaces where visually intricate activities are performed on occasion may require 10-20 foot candles. In general, you should aim for an average of 20-50 foot candles in most spaces. However, there are some places where more or less light may be required.
How many foot-candles are in a 100-watt bulb?
A fourth-generation phosphorescent bulb has an efficacy of about 4 lumens per watt. This implies that a 100-watt bulb will produce 400 lumens - TOTAL. If we COULD reflect all of that light into 1 square foot, we would have a light intensity of 400-foot candles. So, in reality, we would get 1/4 of that light onto a one-foot square, or 100-foot candles.
But we can't reflect all of the light into one square foot; some will be absorbed by the objects in the room, and some will be scattered around the room. So, in reality, we would be lucky to get 50-foot candles from a 100-watt bulb in a reasonably furnished room.
In conclusion, to calculate foot candles, you need to take a reading from the light meter and then multiply it by 10.76. This will give you the number of foot candles in the area that you are measuring. You can also use a light meter to measure the average foot candle reading for an entire room by taking readings in different areas of the room and then averaging them out.
How many foot candles is full sun?
The light produced by the sun is estimated at around 5500 footcandles--nearly full sunshine except during midday, when full summer sunshine in most latitudes may reach 10,000 FC. On a clear day, clean fiberglass usually generates 5000-7000 FC of light.
Full sun is considered to be around 10,000-foot candles. This is the amount of light that you would receive if you were standing in direct sunlight. However, the full sun also depends on the time of day and the season. For example, mid-day during the summer will provide more full sun than early morning or late afternoon.
Why do you need to measure foot candles?
Foot candles are a unit of measurement that is used to determine the amount of light in an area. The more foot candles, the brighter the area will be. Measuring foot candles can be helpful in a number of different situations. For example, if you are trying to calculate the number of lumens required to adequately light a space, you will need to know the square footage of the area and the foot-candle requirement for that particular space. Once you have those two numbers, you can simply multiply them together to calculate the number of lumens required.
Measuring foot candles can also be helpful if you are trying to determine the best way to position lights in a room. By taking measurements in different areas of the room, you can get a good idea of the overall light level in the space and make adjustments accordingly.
In general, measuring foot candles can be helpful in any situation where you need to know the amount of light in a specific area. By taking measurements and calculating the number of foot candles present, you can get a good idea of how much light is needed to adequately illuminate the space.
What is the difference between a lux and a foot-candle?
A lux is a unit of measurement that is used to measure the intensity of light. One lux is equal to one lumen per square meter. A foot-candle is a unit of measurement that is used to measure the amount of light that falls on a given surface. One foot-candle is equal to one lumen per square foot.
The main difference between a lux and a foot-candle is that a lux measures the intensity of light while a foot-candle measures the amount of light that falls on a surface.
What is the difference between a lumen and a foot-candle?
A lumen is a unit of measurement that is used to measure the amount of light that is emitted by a light source. A foot-candle is a unit of measurement that is used to measure the amount of light that falls on a given surface. When you put the bulb in, you can expect that it will give off that quantity of light on a regular basis. So it's installed in your light fixture. But then you decide to cover the fitting with a lampshade.
Is the amount of light in the room changing? No, things are still operating as normal. However, because you've redirected and blocked part of the light, you've affected the quantity of light inside the room; thus, the area under the bulb will not be harmed, but overall illumination in the space will be reduced.
To calculate the number of foot-candles in a room, you need to know the lumen output of the light source and the square footage of the room. To find the lumen output of a light source, you can look at the packaging or label on the light bulb. It should be listed there.
Another simple example is shown below. Most cellphones have a flash that may be used as a torch, so turn it on and hold it over a surface, such as your desk. Now move the phone up and down. The flash stays just as powerful, but the surface grows darker the farther you move the phone away.
You could have a bright lightbulb that's not very efficient. So it emits a lot of lumens, but most of them go in directions other than straight ahead. Conversely, you could have a dim lightbulb that's very efficient. So it doesn't emit many lumens, but most of them head straight out from the bulb.
Final words
Foot-candles are a unit of measurement used to determine the amount of light that falls on a given surface. To calculate the number of foot-candles in a room, you need to know the lumen output of the light source and the square footage of the room.
You can use a lux meter to measure the amount of light in a specific area. However, a foot-candle is a more accurate way to measure the amount of light in a space.
When measuring foot-candles, it is important to keep in mind that shadows and reflective surfaces can affect the readings. For the most accurate results, take measurements in multiple areas of the room and average them together.