I’d like to continue our series on exposure modes. I know it’s been a while, I was just waiting for your comments and photos from the last post. It’s ok, I forgive you, I know you were just waiting until we got to the manual exposure modes so your creative juices can flow free So we pick up where we left off with Aperture Priority Mode (A).
Aperture Priority Mode is the first semi-manual mode that we’ll discuss. This is the first opportunity for you to have some say on how your camera sets it’s exposure. So let’s get to it. What is Aperture Priority Mode?
Aperture Priority Mode allows you to manually set the aperture on the camera and then have the camera set the shutter speed automatically. As you recall from our previous discussions, aperture, controls the size of the opening of the shutter, or how much light is allowed to hit your film or digital sensor during the time the shutter is open. It is measured in f-stops. So why would you want to set your aperture manually when your camera does a perfectly good job of setting it in P-Mode?
Well, you may recall that aperture not only controls the amount light entering the shutter, but also has the side effect of controlling your….come on, you know this one, depth-of-field! This is an excellent reason to override the camera’s settings and set the aperture yourself. Say your taking a portrait of a beautiful model in a lovely woodland setting…what’s that? No models around you say? No problem, let’s say you’re taking a portrait of your cute as can be 10 year old in a lovely woodland setting. Huh? No woods near you….hmmm ok you’re taking a portrait of your cute as can be 10 year old in a very crowded city park.
This situation is even better, you have all these other people around, and even worse they are in the background of this lovely photo that you are trying to take! What are you to do? You turn to Aperture Priority Mode (A) of course. By manually taking over control of the aperture and using a very large aperture setting of say f/1.8 or f/2.8 you can take that beautiful photo of your cute 10 year old and have all those people in the background become just a blur, so the cuteness of your subject shines right through. Like in the example below:
Bird with shallow depth-of-field f/2.8
Ok so my cute 10 year old happens to be a bird The point is that this photo has a very shallow depth-of-field and a lovely blurred background because of the large aperture setting of f/2.8 that was used. Working with the camera in Aperture Priority Mode (A) allowed me to manually set the aperture to f/2.8 and ensure that setting is what the camera would use when it took the photo.
Now those of you have been reading carefully, might think I’ve made a mistake about something. You might even think I’ve completely lost it, because it seems I’ve made that mistake in more than one place. You may be thinking, “dingus over here doesn’t know that 2.8 is a small number..he keeps saying that f/2.8 is a large aperture, how can that be??!!” Let me assure you it is no mistake, and it is something that does take getting used to.
You can think of it like fractions, 1/2 is bigger than 1/10 even though 10 is a larger number. It turns out that aperture numbers work the same way. The larger the f-stop value the smaller the aperture size. You can see an example of this below:
Aperture sizes and depth-of-field (Courtesy of http://howtotakepics.blogspot.com/2009/03/basics-terms-of-dslr-photography.html)
The diagram above clearly illustrates that the larger the aperture, the smaller the f-stop number. You can also see that the larger the aperture, the more shallow your depth-of-field becomes. This is why photographers love to get lenses with the largest aperture possible. Since a larger aperture lets more light in, this allows you to use a faster shutter-speed when shooting in low-light (remember reciprocity from our previous discussion). For those of you that own DSLR cameras, you may have noticed that the lens that is included has an aperture range of approx. f/3.5 – f/5.6. This means that the largest aperture that can be set is f/3.5 and as you “rack-out” your zoom the largest aperture your lens can achieve is only f/5.6. By the way, to rack-out, means to zoom your lens out to the maximum focal length.
This is why camera companies can afford to include these lenses in the kit with your camera. As you can see they do not have a particularly large aperture. Or as we say in the industry, they are not very “fast” lenses. A lens that has a larger aperture compared to another lens is referred to as “faster”. The faster a lens is, the larger the aperture setting that can be used, and also the more expensive it is! You will find that most people who shoot with the lens that came with their camera always feel they cannot get great photos in low-light situations. This is because as we’ve seen before the kit lens is usually not very fast, or the camera companies wouldn’t be able to afford to give it away. It is not uncommon for a photographer to buy a faster lens, either an f/2.8 or f/1.4 after shooting with the kit lens for a while.
We’ve learned before that when shooting portraits a large aperture is usually used to achieve a nice shallow depth-of-field. So what if we’re shooting landscapes? Well for that we want just the opposite, we want to use a very small aperture like f/16 or f/22 (remember small aperture, large f-stop). This will give us a very large depth-of-field or high degree of sharpness throughout the photo. This is exactly what we want for landscapes. Picture a beautiful mountain scene with water, hills, trees, in a photo like this we want to make sure that everything in the scene from the water in front to the mountains in the distance are nice and sharp. How do we do this? With a small aperture of course! Take a look at the example below:
Reservoir, large depth-of-field, f/16
Wow, look at that, not only is everything in the photo nice and sharp because of the small aperture we used, but the content of the photo actually matches what I was describing, how unusual By the way when we want to refer to an area in the photo which stretches on as far as the eye can see past the horizon, such as the one above, we refer to that point as infinity. So for a photo like this you would actually set your focus to infinity when taking the shot.
Now that you have a new creative tool under your belt, go out and start shooting! Don’t be afraid to experiment with your aperture settings. Try out what we talked about above, or mix it up a bit. Sometimes using an unconventional aperture setting can create some very interesting results. Shooting in Aperture Priority Mode (A) really opens up a whole new world of creative possibilities. I actually find that I shoot in Aperture Priority Mode about 90% of the time. And don’t forget that the camera still sets the shutter speed automatically, so the camera still ensures that you get a nice even exposure. That is until next time when we discuss Shutter Priority Mode (S).
Until then, please feel free to comment, ask questions, and absolutely send or post some results!