Lens Aperture and the Lakota Wolf Preserve
On Saturday, Rich and I went to the Lakota Wolf Preserve in upstate New Jersey. They offer serious photographers the opportunity to walk within two sets of wire fences. There are panels cut through the interior fence allowing photographers to get an unobstructed view of the wolves. However, the fee for the privilege is several hundred dollars. While I’m all for the money going to the preserve to help care for the wolves while giving the ability to take some nice photos (and maybe one day I will), there were other factors that swayed us away for the higher price tag: We simply wanted a couple decent photos to remember the experience, and there was only one camera between us. Thus, we took the far less expensive $15 tour that kept us on the outside of the two fences. It didn’t take long for me to realize that it meant photographing through two sets of fences. After some experimenting with settings and watching the angle of the light, I was able to take some photos that look as though there was no fence, or, at worse, a pale shadow of the fence.
When my husband saw the pictures, he asked “How did you do that?”
I also received some email asking how I was able to blur out the background of the butterfly pictures. The very short answer to both questions: Watching the light and adjusting the aperture. Watching the light simply means seeing where the angle the light is coming from, its intensity, and how it may affect the subject of the photograph. Some photographic terms for defining how that light interacts with your camera are:
Aperture: It defines the diameter of the lens opening and how much light comes into the camera. The size of the aperture is defined by the f-stop. The “f” stands for fraction of a focal length. Focal length is also referred to as depth of field.
Shutter Speed: how long the light is allowed into the camera.
ISO (or ASA) defines how sensitive the sensor (or film) is to light.
How you use the aperture, shutter speed, and ISO is a sea-sawing balancing act to get the end result that you desire. Luckily, when using a digital camera, you can immediately see your results and make changes as required.
Shutter speed makes sense: The longer the camera shutter is open, the more light that hits the sensor (or film). If you’ve used film, you probably remember buying 100 ASA film, 400 ASA film, and even faster films. Most people generally used 100 because it gave very good results in most lighting situations. While not exactly, ISO is like the digital equivalent of ASA. Generally the camera defaults to 100, and sometimes people increase this number as the lighting decreases. Like with film, the higher the number, the greater the risk of having a grainy image. Both shutter speed and ISO are relatively clear. It’s f-stops, however, that can get tricky.
If you’ve used a 35mm camera , you probably remember the series of numbers on the lens. Those numbers are the f-stops — for example, f/2 to f/32. There is a mathematical explanation between the progression of f-stops. Each successive f-stop allows in half of the incoming light. In other words, the f/4 setting allows in half of the light as the f/2.8 setting. The f/2.8 setting uses half of the light as the f/2 setting. The term “stopping down” means allowing in half of the light. You don’t need to know this math unless you want to. What is helpful to understand, however, is the following:
The smaller the f-stop (F2), the larger the aperture and also the wider the stream of light coming into the camera. The larger that aperture, the less the overall image is in focus and the smaller the depth of field. A small f-stop is ideal for photographing a butterfly. It keeps the focus on the butterfly and blurs out everything else. A smaller f-stop can work nicely when photographing a person.
- Small f-stop = large aperture or wide light beam = smaller focus area
(small depth of field)
The higher the f-stop (F22), the smaller the aperture, meaning the more narrow the stream of light that comes into the camera. The small the aperture, the more in focus, and greater the depth of field. A high f-stop is ideal for photographing a landscape.
- High f-stop= smaller aperture or less wide light beam = greater focus of wide area
(large depth of field)
It seems counter intuitive, as it would seem that the larger number would indicate the more light coming in. But, not so. Think of quilting needles — the higher the quilting needle size, the smaller the eye of the needle. With f-stops, the higher the number the more depth of field because of the smaller aperture opening.
I really do get dyslexic with this stuff, and when I’m shooting I often think: small f-stop, small focus; high f-stop, wide focus.
This image has a medium high f-stop. The higher f-stop means more of the image is in focus. This is why the fence, especially around the area of the wolf’s head, is in focus. However, you can also see how the depth of field is graduating from somewhat out of focus to in focus.
This is taken from the same location, but this time I widened the aperture, meaning I used a smaller f-stop which results in the focus being on the subject itself. This means that the fence in front of the wolf is a bit blurred, and the area behind the wolf is a bit blurred. Neither is very blurred because the wolf was relatively close to the fence. Even so, I like this image better than the one above it. Editing away the fence in this image would be far easier than in the image above it.
Here’s another example. In this case, the fence is still visible, but not as distracting as it would otherwise be had I used a higher f-stop and the focus is still on the wolf.
Many cameras come with pre-programmed settings such as a close-up, a landscape setting, a person in the foreground and focus in the background, and so on. In those cases, the camera is controlling the aperture and shutter speed for you (based on the ISO setting you’re using). If you have aperture priority, that means you can set the f-stop and let the camera figure out the faster shutter speed it can use. Shutter priority means you define how fast you want the shutter speed and it balances out the aperture. Understanding these principals allows you to know when you may want to override your camera’s programmed settings.
In this example, the focus is on the head of the wolf and the nearby greenery.
Here’s another way to think of aperture and f-stops. Think of a large circle, that circle can represent an f/2 aperture. Then think of a series of progressively smaller circles, all within the large circle. Each of the progressively smaller circles have a progressively higher f-stop number and each smaller circle lets in less light. It’s the large circle that is the constant. The aperture can close smaller, but it can never open larger than the largest aperture of the lens. And this is a prime reason why a “fast” 200mm lens can cost far more money than a much “slower” 200mm lens. The wider aperture can allow in more light, meaning you can use it in a low light situation, but it can always be stopped down to let in less light. However, a lens with a small aperture to begin with can only allow in so much light at its widest setting. Thus, in the same lighting situation, one lens could require a tripod or flash, while another may allow in enough light so that neither a tripod or flash is needed. But, again, it’s all a balancing act between aperture, shutter speed, ISO, available light, and even your subject (is it moving like in a sporting event or stable like in a landscape).
Here are a few more images using a smaller f-stop.
In this image, the fence is hardly visible at all.
While the fence is a bit visible in certain areas, it also looks like sunlight reflecting off of something like tree leaves.
When I was fooling with settings and looking at the results (I was using a digital camera), I realized that the placement of the wolf’s eyes affected the quality of the image. When possible, I tried lining up the eyes within the space between the wire of the fences. Otherwise, the eyes appeared less in focus because the wire of the fence was blurred in front of the eye.
None of these images are incredible (although I am partial to a couple of them), and they are a bit “soft” because of having a blurred fence in front of the subject, but they all are better than they would have been if the fence was prominent.
So, to answer the question of how I photographed the wolves and the butterflies: I used a fairly decent lens with its lowest f-stop, I watched the angle of the light, and I focused on the eyes of the wolf or the head of the butterfly.
July 28th, 2008 at 9:37 pm
Thank you for taking the time to explain something I have been trying to make sense of on my Canon Powershot. I seem to get overexposed pictures when I use the auto setting, so I’ve started playing with the more manual choices I have. Your explanation of the f-stop is the clearest I’ve found. (I’m sure my frustrated amateur photographer brother would thank you, being my tech support is not always easy!)
And, I love the photos of the wolves!
July 28th, 2008 at 11:58 pm
Thanks Beverly. I’m glad it’s helpful. Regarding your overexposed photos, see if you have the plus/minus setting. If you’re getting consistent overexposed pictures, set the plus/minus to something like -05. Take a picture and see if it makes a difference. If not, try it with -1.0 and so on. It’s a very handy feature. It’s a quick way to “stop down” or let in less light.
October 1st, 2008 at 9:33 am
Thanks Gloria. I am going to go and have a play with the manual parts of my camera.