The digital camera system you're using in the clinic is a wonderfully creative tool; it can do so much more than the intraoral photos you make every day. Whenever I do a photography training session in the clinic, I usually get asked a lot of questions about using the camera to have fun outside the office. And it
is fun!
In this post we're going to look at just two little things you can do with your camera that will make a big difference in your photography: controlling the shutter speed and controlling the aperture.
Here's that Command Dial on top of your camera; you'll recognize it from our training sessions. When we're making intraoral photos with the Macro Lens and Ringflash, we leave it on "M" (Manual) so that the flash can create proper TTL exposures for us. Let's remove that flash and go outside to explore our creative possibilities!
Let's first set it on "Tv" (Time Value) so we can set the shutter speed to capture the action of a fast-moving subject. As long as the overall light level is pretty good (a nice sunny day) the camera will automatically select an aperture that will yield a good exposure.
On the right is an extreme example of that: the water fountain on the Stanford campus. I wanted to see what it would look like if I "froze" the water droplets with a really fast shutter speed. I jacked up the ISO to 6400 to take advantage of as much light as I could, and used a shutter speed of 1/8000 of a second! Think about other kinds of subjects that could use fast shutter times, such as racing bikes and football players, or the fastest subjects of them all: your kids.
Here are a couple examples of going in the opposite direction; very
long (slow) shutter speeds that capture the flow of moving water. Of course, such long exposure time usually requires a tripod to keep the image sharp overall. The river was shot at 1/4 of a second, and the waterfall at 1/3. In human terms those don't seem like overly long durations, but in photo terms those are long exposure times indeed.
Now let's go in the opposite direction and set the camera to "Av" (Aperture value) which will allow us to control depth-of-field through aperture selection, and the camera will automatically set an appropriate shutter speed. The higher numbers (f 22, f 32 for example) give us a lot of depth-of-field, which we need in images such as landscapes. We use f 32 for all our intraoral imaging for exactly that reason, too. If you look closely at that picture of the waterfall, you'll see that in terms of sharpness, everything from the bush in the foreground to the hilltop in the distance is sharply in focus; that image was exposed at f16.
But what happens when we go in the other direction?
Here's an image showing the
least amount of depth-of-field possible; it was photographed at f2.8, which is the "widest" that particular lens could go. Other lenses (considered "faster") may allow for f1.8, even f1.2!
This kind of imaging creates a lot of separation between the subject and the background, making the subject stand out dramatically. Portraits are nearly always taken in this manner, for example.
I know this is a pretty cursory description of the relationship between shutter speed and aperture, and you probably have more questions now than you did before. That's a good thing! Explore and try things out. You aren't going to break the camera, and you'll discover amazing things about photography -- and yourself! -- in the process.
We'll look at some other creative, outside-the-office techniques down the road. And I hope that road is a long, scenic drive.
Later, amigos!
dhutt@dmddigitalphoto.com
Dave
