Although I’ve categorized this post as related to Integrated Clusters, I’ve done that for my own ease of finding it in the future. The post is really about Design Thinking which I think is critical to the success of the cluster initiative.
I’ve been thinking a lot about the design of everyday things because I’ve been reading the book of that name. It’s an eye-opening book that will make you question all of the made objects that you encounter in a given day. I can’t recommend the book highly enough for anyone who has ever been frustrated by not being able to figure out how to use a particular product. The book has also made me think a lot about the design of everyday experiences, especially student experiences, which is making me rethink a lot about my teaching and the way the University does things. It has made me think about the world around me in new ways.
At the same time, I’ve been thinking a lot about photography. I’ve loved making photographs for a long time but, in recent years, had not spent much time on this hobby. After reading Designing Your Life, I decided to carve out time to work on my photography skills and knowledge as a way to introduce more play into my life and as a stress reliever. I’ve been making a lot of photographs, following a bunch of photography blogs, and challenging myself to try new things photographically. I also bought myself a new camera which I’m still figuring out how to use.
I was working on exposure the other day. I was experimenting with various combinations of ISO, aperture, and shutter speed to see what the results looked like. I learned about the exposure triangle back in the days of film cameras and continued to use the principles after I moved to digital cameras. But I haven’t really thought about how these three settings work together to capture light in a long time.
I know that back in the days of film, ISO was a measurement of the film’s sensitivity to light. There are light-sensitive particles on film and the ISO represents how big these particle are. The lower the ISO, the smaller (finer) the individual particles are and so, the less sensitive to light each of them is. Bigger particles are more sensitive to light. Roughly speaking, ISO 200 film is twice as sensitive to light as ISO 100 film. The general rule is to use the least light-sensitive film you can because those larger particles can show up as grainy in the final photo. This issue is such a concern, especially in color photos, that some photographers will not shoot color film with an ISO greater than 200.
So if you know you are going to have plenty of light (a sunny day, for example), use a relatively light-insensitive film (ISO 100 or 200) and then adjust the shutter speed (how long the shutter remains open) and aperture (how big or small the opening on the lens is) so that the appropriate amount of light hits the film for the appropriate amount of time to render a properly exposed image. If you know there is going to be less light, choose faster film (more light-sensitive, ISO 400, 800, 1600, or even 3200) so that you can use reasonable shutter speeds and apertures to get the same level of exposure as the sunny day with ISO 100 or 200. The price you pay for choosing faster film, however, is graininess in the resulting photos.
One of the first things I noticed about my new camera was that the range for ISO is 100-25600. That is a much bigger range of ISO than is available for film where I’ve never used faster than ISO 1600 (and that was a rare occurrence) although I know ISO 3200 and even ISO 6400 exists. This got me thinking about ISO on a digital camera. If ISO is the size of the light-sensitive particles on film, what would it represent in a digital camera? Changing the ISO definitely doesn’t change the size of a sensor in a digital camera so in what way would it measure sensitivity to light? I knew that the camera’s sensor is made of millions of photosensitive diodes, the number of which represent the resolution (number of pixels) of the camera. But it made no sense to me that the ISO would change how sensitive these diodes are to light. So I started doing some research. (If you aren’t interested in the details of how digital cameras work, skip the next paragraph.)
Although many of the articles I read say that ISO is a measure of the camera’s sensitivity to light with no further explanation, it turns out that ISO in a digital camera isn’t about changing the light sensitivity of the diodes on the sensor. When light hits the digital sensor, each diode accumulates an electric charge which represents the brightness of the light. More light on a diode results in a higher charge. When the shutter closes, these electric charges are converted into numbers (which is why these cameras are called “digital”) and stored. Software is used to turn these numbers back into an image for us to view. (The story is a bit more complicated because these diodes only capture brightness and not color. Color is recorded in a different way but to understand ISO, we’re only interested in brightness.) Because a digital camera is a computer, it can boost, or amplify, the electrical signals that hit the diodes. ISO is an amplification factor. That is, if a certain amount of light results in a certain electrical signal at ISO 100, half of that light will result in the same electrical signal at ISO 200 because the camera amplifies (doubles, in this case) the signal. If less light is available, a higher ISO is required for an exposure similar to one with more light at a lower ISO. Digital cameras have a similar problem as film cameras at high ISO in that digital images recorded at high ISO can look “noisy” in a way that is similar to the graininess on film that I wrote about earlier. This is because the diodes can only capture a certain amount of light before their electrical signal reaches the maximum possible. Any light beyond that point results in the diode “blowing out.” Think of blown out fuses in your house. When a diode is blown out, its electrical signal leaks over into other diodes which further amplifies their signals, increasing the possibility that they will blow out as well. (As an aside, digital cameras allow shooting at much higher ISOs than film cameras because diodes can handle a pretty high signal before blowing out. That’s why the ISO range for my camera goes to 25600 while film rarely goes above 3200.) The rule for digital photographers is the same as for film photographers. Shoot at the lowest ISO possible to capture the appropriate exposure for your image.
So what does all of this have to do with design thinking? All digital cameras that allow exposure control have settings for ISO, a concept that is a holdover from the days of film cameras. ISO in film is about light sensitivity. Even though the digital photographer cannot change the light sensitivity of a digital sensor, early digital camera designers recognized that legions of film photographers already understood that concept. Rather than introduce an entirely new (and more difficult to understand) concept called “boost factor” or “amplification” (which would be more accurate), these early designers made the choice to design their cameras so that film photographers could easily make the switch from film. After years of design and development of digital cameras, the common (mis)understanding of ISO as light sensitivity is so widespread that nearly every beginners’ explanation of ISO that I encountered in my research repeats it. And why not? ISO in digital cameras combines with shutter speed and aperture to create the exact same exposure triangle as ISO in film cameras did. (Mis)understanding ISO as light sensitivity allows digital photographers to properly expose their images when they combine that (mis)understanding with an accurate understanding of aperture and shutter speed. I think there might be lessons for us from this design story as we move forward with our redesign of the University. As we redesign the University, we need to think carefully about how we explain the University and how it works to students, faculty, staff, and external partners. We should try to keep our explanations clear, even if sometimes they aren’t entirely accurate.
By the way, in case there was any doubt that I am a geek, doing this research about how digital cameras actually work was really fun for me!