Aperture Priority Mode

All posts tagged Aperture Priority Mode


We’ve finally made it to the end of our 5-part series on exposure modes. We finish with the king of all creativity, Manual Mode. This is the mode that lets your knowledge of photography and creativity shine through. Manual Mode is the one where you basically tell the camera to “shut-up” and let you do the driving.

Are you in a dark room where the camera is telling you it’s too dark to make  a proper exposure? No problem, Manual Mode will let you take that photo. Do you want to take a photo with a very deep depth of field and also freeze the action, but don’t have enough light? Switch to Manual Mode, and give it a shot, you’re not paying for film!

Ok ok, so Manual Mode is not a magical cure for exposure problems, but it does allow you to go out of your camera’s, and possibly your, comfort zone to take some photos that the camera might not allow you to take while in one of the other exposure modes.

Let’s review a bit…we’ve already learned about the other 3 exposure modes..

Programmed Auto Mode (P-Mode) your camera does all the thinking. Aperture and shutter speed are set for you automatically.

Aperture Mode (A-Mode) you set the aperture and the camera determines the shutter speed for you.

Shutter Mode (S-Mode) does just the opposite, you set the shutter speed and the camera sets the aperture value.

By now I’m sure you have guessed that in Manual Mode (M-Mode) you’re flying solo. You’re responsible for  setting both the aperture and the shutter speed yourself. That’s a big responsibility! Are you ready for it? Can you handle it? I think you can.

Even if you don’t think you’re quite ready, I implore you to try Manual Mode. Nothing will teach you about exposure settings and the relationship between aperture value and shutter speed faster than being out there on your own making your own exposure settings.

Plus, if you make a mistake, you might it’s a part of life, because you’re shooting digital it costs you nothing to try, and it’ll be our little secret if it doesn’t turn out quite right the first time. If you’re shooting film however, you may want to borrow your friend’s digital camera to try it out. You’ll most likely be going through a lot of frames, plus the digital camera allows you to get instant feedback, instead of having to wait for the film to be developed to see what worked and what didn’t.

The toughest thing to shooting in Manual Mode is picking a starting point. When choosing your aperture and shutter speed where do you begin? It can be very overwhelming. Sometimes when shooting in Manual Mode professional photographers will use a light meter. A light meter is a hand-held device that measures the light in the scene around you and gives you values for what your aperture and shutter speed should be.

Now wait a minute…that sounds just like what your camera does when it is in P-Mode. Well you’re right, your camera has a built-in light meter which is how it determines the proper exposure values for the scene you are shooting. So what do you do when you’re new to Manual Mode and your light meter is in the shop? Put your camera in P-Mode and press the shutter down half-way.

This is going to give you an exposure reading. In P-Mode the camera will use it’s built-in light meter to “read” or “meter” the scene and tell you the aperture and shutter values that it comes up with. So now armed with this new information we can switch back to Manual Mode and plug in those values we just got from the camera’s built-in light meter. You now have an excellent starting point for setting up your shot in Manual Mode.

You know these values are going to give you a relatively decent exposure to begin with, so now you can start getting creative by varying either the aperture value or shutter speed to achieve your desired results. Want a shallower depth-of-field? Go ahead and dial in a larger aperture value, just keep in mind that you’ll need to adjust your shutter speed to keep your exposure well balanced.

A good rule-of-thumb to remember is that for every full stop of aperture value you increase or decrease you should also change your shutter speed by a full stop to maintain the same Exposure Value (EV). We learned about this a while back when we discussed reciprocity.

So for example, if our light meter (built-in or hand-held) chooses an aperture of f/8 and a shutter speed of 1/125 and we want a shallower depth-of-field. We can change our aperture value to f/4. That is a change of 2 full stops. So in order to keep the same Exposure Value (EV) we will need to raise our shutter speed by 2 full stops bringing us to a shutter speed of f/500.

This is because when we make our aperture value larger by a full stop we are letting in double the light. Since we changed our aperture from f/8 to f/4, 2 full stops, we are now letting in 4 times the light at f/4 than we did at f/8. So to compensate we use a faster shutter speed by 2 stops from 1/125 to 1/500. This causes 1/4 of the light to be let in at 1/500 than we had at 1/125 which cancels out the 4 times more light coming in from our aperture value.

How do I know that is 2 full stops you ask? Well I have included a chart at the end of this article that shows the full stop values for both aperture and shutter speed. Some high-end cameras will let you change your aperture or shutter speed in 1/2 or 1/3 stops as well, but all cameras will let you dial in full stop values.

Manual Mode also comes in very handy when shooting with flash, especially external flash. A full discussion on shooting with external flash is a topic for another blog post, but we’ll touch on it briefly. When shooting with an external flash the cameras light meter may not take this into account. Therefore it might choose a very slow shutter speed automatically for you because it is metering the available light in the scene. The light meter may not know that an external flash will be used. This is the perfect time for Manual Mode.

By shooting the scene in Manual Mode you are able to tell the camera that you would like to use a faster shutter speed. We know this still will result in a good exposure because the flash is going to provide quite a bit of light to our scene. Shooting in Manual Mode let’s you choose the shutter speed and also the aperture value that will work for your flash lit scene.

There are some people who are perfectly content taking all of their photos in P-Mode and letting the camera do all their thinking. Most of the time this yields decent photos. However, you cannot truly begin to explore the creative possibilities of photography or take your photos to the next level until you turn that dial and try shooting in one of the other 3 modes.

Maybe you feel Manual Mode is a bit too much for you to try right now, but Aperture Priority Mode or Shutter Priority Mode are just begging for you to give them a shot. They let you start taking control of the exposure in your photos without having to fly solo. And as with most things, there is no better way to fully understand your cameras exposure modes than to get out there and shoot as much as you can!

I hope you’ve enjoyed this multi-part series about exposure modes, even if the end was a long time coming. Feel free to ask questions, leave comments, and share your creative photos. Until next time.

Exposure Value Chart

Chart of full stop values and Exposure Values (EV), Courtesy of thecrosseyedbear on Flickr http://www.flickr.com/photos/thecrosseyedbear/2124175721/

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

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)

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

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!