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Old 06-07-2018, 08:39 PM   #1
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Light Bulb Coverage Area


Is there an easy way to calculate the coverage area of a light bulb based on its wattage and/or lumens?

Assuming the bulb is used in the dark with a 180 degree spectrum with nothing to obstruct its coverage.

I am trying to figure out how many bulbs I will need to cover an area of 20' x 25'.

Thanks
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Old 06-07-2018, 09:07 PM   #2
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Re: Light Bulb Coverage Area


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Old 06-07-2018, 09:21 PM   #3
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Re: Light Bulb Coverage Area


There are many factors to consider besides room size. Height of the ceiling; level of light required for the tasks that will be done; the type of light fixture and how it projects the light from the bulb.



You might find this post over in another forum helpful.



http://forums.mikeholt.com/showthrea...800#post400800
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Old 06-07-2018, 09:28 PM   #4
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Re: Light Bulb Coverage Area


Thanks, I should have mentioned that this is for outdoor lighting on my patio. so the ceiling is over 100,000 feet, hehe

The height of the fixtures is another question I didnt get to yet. This is more of nighttime hanging out lighting so probably 3000K. Light fixture hasnt been decided on yet but I am looking.

Last edited by DeeEyeWhy; 06-07-2018 at 09:30 PM.
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Old 06-07-2018, 09:40 PM   #5
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Re: Light Bulb Coverage Area


Ok, I understand. Still, the height of the fixture from the ground will matter, as will whether the fixture has any kind of reflector, or whether it is just a bare bulb hanging from a wire. With a bare bulb, figure that around 50% of the light output will be lost in upward direction.
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Old 06-07-2018, 10:08 PM   #6
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Re: Light Bulb Coverage Area


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Originally Posted by RAL238 View Post
Ok, I understand. Still, the height of the fixture from the ground will matter, as will whether the fixture has any kind of reflector, or whether it is just a bare bulb hanging from a wire. With a bare bulb, figure that around 50% of the light output will be lost in upward direction.
Thanks, I was originally thinking of using about two or three wall sconces similar to this one:

https://www.amazon.com/Callaway-Bron...+wall+lighting

or this:

https://www.amazon.com/Naturous-Outd...+wall+lighting

In terms of fixture height what would you recommend?
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Old 06-07-2018, 11:29 PM   #7
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Re: Light Bulb Coverage Area


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Originally Posted by DeeEyeWhy View Post
In terms of fixture height what would you recommend?

This is where you start to open the can of worms.


I'm guessing this will be for folks sitting in chairs or at tables. Will the lights be mounted on poles? On the wall of the house? Somewhere else?



I'd probably choose a height of 6 or 7 feet, just as a number pulled out of the air. If you go higher than that, you'll have less light per fixture at seat level.



A lot depends on how bright you want things. Bright enough to read by? Dim enough to just be able to tell who the person is you're talking to?



I use 4 50W PAR20 bulbs on a dimmer in a ceiling fixture 9 feet off the floor to light a 18' x 20' porch. They provide enough light read by at 100%, and mostly we keep it well below that. But those bulbs provide more focused light than the fixtures you're talking about.
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Old 06-07-2018, 11:35 PM   #8
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Re: Light Bulb Coverage Area


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Originally Posted by RAL238 View Post
This is where you start to open the can of worms.


I'm guessing this will be for folks sitting in chairs or at tables. Will the lights be mounted on poles? On the wall of the house? Somewhere else?



I'd probably choose a height of 6 or 7 feet, just as a number pulled out of the air. If you go higher than that, you'll have less light per fixture at seat level.



A lot depends on how bright you want things. Bright enough to read by? Dim enough to just be able to tell who the person is you're talking to?



I use 4 50W PAR20 bulbs on a dimmer in a ceiling fixture 9 feet off the floor to light a 18' x 20' porch. They provide enough light read by at 100%, and mostly we keep it well below that. But those bulbs provide more focused light than the fixtures you're talking about.
The lights will go on the house.

Now I know there are other lighting options (rope lights, string lights, etc...), but those are plug-ins that can go on when needed, but this is definitely general night-time family hanging out, having a beer, etc... Definitely not reading a book lighting...

Also my patio is open no awning or anything above it...

P.S. I like opening cans of worms. My wife may disagree with me, but that's usually how the can gets opened, LOL...

Last edited by DeeEyeWhy; 06-07-2018 at 11:38 PM.
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Old 06-08-2018, 09:31 AM   #9
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Re: Light Bulb Coverage Area


Quote:
Originally Posted by RAL238 View Post
This is where you start to open the can of worms.


I'm guessing this will be for folks sitting in chairs or at tables. Will the lights be mounted on poles? On the wall of the house? Somewhere else?



I'd probably choose a height of 6 or 7 feet, just as a number pulled out of the air. If you go higher than that, you'll have less light per fixture at seat level.



A lot depends on how bright you want things. Bright enough to read by? Dim enough to just be able to tell who the person is you're talking to?



I use 4 50W PAR20 bulbs on a dimmer in a ceiling fixture 9 feet off the floor to light a 18' x 20' porch. They provide enough light read by at 100%, and mostly we keep it well below that. But those bulbs provide more focused light than the fixtures you're talking about.
Quote:
Originally Posted by DeeEyeWhy View Post
The lights will go on the house.

Now I know there are other lighting options (rope lights, string lights, etc...), but those are plug-ins that can go on when needed, but this is definitely general night-time family hanging out, having a beer, etc... Definitely not reading a book lighting...

Also my patio is open no awning or anything above it...

P.S. I like opening cans of worms. My wife may disagree with me, but that's usually how the can gets opened, LOL...
Based on my measurements, If I put the lights 6 ft from the ground I can put about 3 of them. Do you think that would be enough?

NOTE: I have a bay window in the middle of the back wall so if I put the lights higher i wont have room for 3, only 2. The window is 6 ft and a couple of inches high so the light would go right under the window at 6 ft.
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Old 06-08-2018, 09:53 AM   #10
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Re: Light Bulb Coverage Area


Here's something you could try. Get one of the fixtures and connect it to a length of zip cord as a line cord. Plug it in and then, when its dark, hold the fixture up against the wall in several different spots to see how well it lights things. That'll give you a pretty good idea of whether you'll be satisfied before you drill any holes or pull wires.
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Old 06-08-2018, 10:02 AM   #11
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Re: Light Bulb Coverage Area


Quote:
Originally Posted by RAL238 View Post
Here's something you could try. Get one of the fixtures and connect it to a length of zip cord as a line cord. Plug it in and then, when its dark, hold the fixture up against the wall in several different spots to see how well it lights things. That'll give you a pretty good idea of whether you'll be satisfied before you drill any holes or pull wires.
Do you mean wire the fixture to something like this and plug it in an outlet:

https://www.amazon.com/Power-Cord-3-.../dp/B0069VW6K6
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Old 06-08-2018, 10:11 AM   #12
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Re: Light Bulb Coverage Area


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Originally Posted by DeeEyeWhy View Post
Do you mean wire the fixture to something like this and plug it in an outlet:

https://www.amazon.com/Power-Cord-3-.../dp/B0069VW6K6

Yes, that will work.
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Old 06-08-2018, 10:15 AM   #13
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Re: Light Bulb Coverage Area


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Originally Posted by RAL238 View Post
Yes, that will work.
Ok Thanks. I'll do that.

Since I dont have the fixtures yet. i guess my next question would be the type of design. It seems logical that a clear glass would emit more light than a frosted glass for example and a downlight like in my examples in previous post would give off less light than a traditional sconce fixture that emits light from all sides.
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