This is the second part of our article about what is a good light bulb wattage for reading and is part 2. The first part can be found here.
Light Shades and Glare
So, it would be all very well if all the light from our bulb fell on a nice handy 3ft square area so we could quickly convert from lumens to lux. However if you have a quick look at your lamps you will notice that they have a shade and this can direct light in all sorts of directions.
In my living room we have two floor lamps. Firstly, one has a round shade. In this case just a big strip of material that runs round the bulb. Since the bulb is pointing upward in the light fitting most of the light from this lamp goes upwards. While good for providing generally lighting to the room, poor for reading. Second lamp has a chopped off pyramid shaped shade. Effectively the top part is open but smaller than the bottom opening. The inside of the shade is white and this directs the light downwards, making it much better for reading.
In my home office there are a couple of desk lamps. These have a half spherical metal shade which gives a very directed light focused on a small area. Good for detailed work. However the bulbs in these lamps are teardrop shaped and longer than the shade thus providing a lot of glare. Glare occurs when light is reflected off a surface, or shines directly into our eyes. This direct light causes our eyes to contract as well as interfering with the light coming back from the page that we are reading.
As an illustration, I am reading in my favorite chair under my reading lamp with the rest of the lights off, comfortable in a pool of warming reading light. Thus, saving on my electricity costs. Sounds good, but in fact it is a poor situation for reading. The eye wanders away from the page I am reading and then returns back to it. If the rest of the room is in darkness my eyes dilate when I look away and then have to refocus when I look back. This fatigues my eyes. I need to avoid this high level of contrast within the room I am reading in. Additionally, this occurs even more when 1 am reading in bed with my book light.
So what should we do?
Overall you should have a translucent (partially see through) shade for the lamp you are using for reading. The shade must be sufficiently opaque so that you cannot see the bulb directly as this will cause glare when reading. It should direct the light downwards for reading but also allow the surrounding area to be illuminated to avoid issues of contrast.
The direct reading area, where you have your book, should be lit by a significant amount of light, enough to make reading comfortable. Then the surrounding area should have a reasonable level of ambient light. There should be no glare or light entering directly into our eyes and the light we are using should not create shadows in our reading area.
What Bulb to Choose?
So once we have chosen our best lamp, with a good shade, we now need to add the correct bulb that sits comfortably within the light shade.
In order to select a good bulb good light bulb for reading. It should provide at least 500 lux to our reading area. So unless we are using a directed reading light it will need to provide more than 500 lumens.
If we look at a few standard bulbs from GE
GE LED 60-Watt Equivalent (actually 9 watts)
GE LED 100-Watt Equivalent (actually 13.5 watts)
GE LED 150-Watt Equivalent (actually 23 watts)
GE LED 200-Watt Equivalent (actually 13.5 watts)
Depending on your light shade and reading setup you will likely need to use either a 100 or 150 Watt equivalent. My floor lamp with the pyramid shade gives 300 lux from my current 1600 lumen bulb. This means I will need to buy a 150 watt equivalent to provide the required 500 lux.
GE also sell a 3-Way bulb that can be used with lamps with 3 way sockets so you can switch between the 3 levels of brightness. This provided the equivalent of 50/100/150watts with 615/1540/2155 lumens. This is a pretty good choice of light bulb wattage for reading.
If you have a lamp allowing this three was switching then this is an excellent option. Due to the higher providing significant light for reading and the lower rating generating enough output for ambient lighting.
If you are reading in the evening you should also get a bulb that has a warm or soft tone. Light is part of our daily circadian rhyme and tells the body it is time to wake up (see our article on sun light bulbs here). Not something you want to do just before bedtime. Light bulbs can supply light in different temperatures measured in Kelvin (K).
1000 to 3000
3000 to 5000
5000 to 7000
There is a lot to consider about what is a good light bulb wattage for reading (part 2).
And, if you are like me and find your eyes tired when you are reading that novel at bedtime it is quite likely that you do not have sufficient light for reading. In writing this article I realized that the lamps in my living room were the wrong way round. The one for reading used for general light. Also, that the bulbs in the lamps in my office stick out and shine in my eyes. And that the bedside lights in the bedroom are completely inadequate. My apartment does not get a lot of natural sun light and all of the electric lighting is not adequate for reading.
What you need to do is check your reading set-up. If possible download a light meter onto your phone (there are free ones). Then make sure you have the right light shades and that the bulb is completely covered by the shade. Then buy the correct wattage, likely a 150 Watt equivalent. If you have dimmers or a switchable light then make sure the top light available is sufficient.
Then sit back and relax in the warm glow of your correct bulb and allow your eyes to relax with a good book.
The following sources were extremely useful in creating this article on a good light bulb wattage for reading (part 2).