Or we don’t know how much we want. When dealing with how much light we need to do certain tasks, we usually have no idea how much light we actually need. This is a major issue in the Illuminating Engineering Society (IES). They are responsible for creating guidelines in how much light we need for each and every task imaginable; everything from parking your car, to eating in café.
About 50 years ago, when energy was cheap, we thought the more the better. By blasting lots of light everywhere, we were guaranteed enough light to see what we were doing. Not only are there numerous aesthetic issues with this, but there are obvious energy issues as well. This has changed throughout the years and the IES now recommends tailored light levels for each task. Energy was the main driving force behind this change in thinking.
But in order to convince the general public and the skeptics out there, the IES and lighting designers relied on sensation and perception basics to back up their lower light levels. In particular they relied on Stevens’ Power Law (P=KSn). When n < 1, the doubling of physical intensity results in less than a doubling of perceived magnitude. So when blasting light everywhere and achieving a high light level, you were also creating a high perceived magnitude. But by just reducing the light level by half, you lessened the perceived magnitude, but by less than half. So just by getting a little bit more specific with your light levels and lowering them overall, you can actually achieve close to perceived magnitude light levels. Therefore, they argued, blasting light everywhere is not an efficient use of the human eye’s perception. A lower tailored level of light with each task attempts to be the most efficient use of energy as well as our visual perception of magnitude.
The photo above is an example of seeing brightness in darkness. We perceive the lamp as very bright, even though the light level is very low. This is an efficient use of our eye’s visual perception.
Not only do I think that this is a really good way to think about the efficiency of light usage, but as I read this article I was also thinking about the importance, usefulness and effect that different levels of light actually have on us. As stated in a previous comment, computers and phones now come with the option to dim the screen light, which is amazing for me, since my eyes are very sensitive to light, especially in dark conditions. One thing that came to mind for me while reading this was not necessarily the monetary costs of using too much light, but also costs in other areas of life.
For one, I have trouble driving at night because as I already mentioned, my eyes are very sensitive to light. I know that many different things can cause this, but for me it is mainly that a medication I’m on dilates my pupils enormously – which doesn’t really seem like it would be too bad of a side effect, but it actually does pose some problems. With that being said, lights in the dark (street lamps, stop lights, head lights, etc.) look crazy to me. For lack of a more appropriate example, think of how everyone at raves is so mesmerized by the light shows, finger lights, light up hoops, fireworks and really anything that lights up or glows. This is because their eyes are outrageously dilated (for other reasons…) making them super sensitive to any kind of light. It’s the same thing with me for head lights and such, except I don’t fall in love with them, I just find them to be a problem and extremely distracting, which is why I try to avoid driving at night if I can (and also why I love raves….). I find that when there are street lights or head lights facing me, it really drowns out everything else in my field of vision, meaning that I don’t really notice people on the sidewalk, bikes, etc. as well as I should — an obvious danger while driving. So, for myself, I find that when things are TOO bright in the midst of darkness, it actually makes HARDER for me to see things clearly.
On a somewhat unrelated side note: The type of light being used makes a huge difference too. In my town at home (and I’m sure many others) streetlights are being replaced from those orange-y bulbs to white bulbs. While this does seem to make it a lot brighter, it’s because studies have shown that the yellow light is known to make people feel more tired, while white light is known to keep people more awake and alert. I’m not sure why different kinds of light affect energy levels in that way; maybe we’ll talk about that in class? Also, another personal example: I have a ton of trouble sleeping almost all the time. I’m often awake until 5-6am just rolling around pissed that I’m not asleep. I’ve tried a billion different remedies for this, and one that my mom came up with was a problem with light. I don’t know much about it, and I’m not sure where she found this — but I’m sure it’d be interesting to learn. What she told me is that she read somewhere that electronics such as cell phone screens, computer screens, TVs, etc. emit blue light, which is known to mess with melatonin levels. Obviously, melatonin levels being messed up is a great explanation for trouble sleeping, so she suggested that I start falling asleep without the TV on, not looking at my phone or computer too long before bed, etc. I don’t know if this is actually proven in any way, but it seems interesting and like a cool thing to look into.
I think your post does an excellent job of applying concepts learned in class to the problems we face in the real world. I have struggled finding an adequate amount of light to see clearly in my apartment without wasting electricity, because i received a $200 electricity bill for January! I have recently found a happy medium. I’ve spaced the lights around the common room of my apartment so they can each illuminate a specific region without too much overlap. I only keep one bright light on in the kitchen during the day, in order to read books and perform simple daily tasks. More lights are honestly distracting, and even more so at night it seems. Because there is very little ambient light coming through the window, after adapting to the darker environment, too many lights causes somewhat of an overload for my retinal processing.
This post also made me think of the function many smart phones have these days which allows them to adjust the screen brightness in response to overall illumination. You can generally turn on “auto” brightness, and your screen will be brighter in the daytime when surrounding light could drown out the picture on your phone. I wonder how phones can detect overall illumination and adapt their screen brightness to better suit one’s eyes. The discoveries we have made about light perception in the past 50 years have led to higher efficiency in street lights, phone screens, and countless other places. This was a very interesting post and i enjoyed reading it.
This is a really interesting way to think about the efficient use of energy in our everyday lives. I remember going out at night last year and measuring light levels around Old Main. I was surprised when the readings were only two or three foot-candles, but the lights seemed so bright against the dark sky. It seems like task lighting is the way to go for new designs so that areas are perceived as bright, but electricity is still being saved. This would probably be much better than the older designs of lighting absolutely everything inside of a building. I bet it’s hard to make a work surface seem bright when your eyes are already adapted to an overly bright room. Hopefully recommended light levels for different spaces continue to be evaluated so that each new design saves more electricity than the last.