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Monday, January 14, 2013

Photography 101 {shooting in Aperture Priority mode}

See I didn't forget about the Photography 101 posts!  They are still coming.  I've been having so much fun with my DSLR mentoring students that I've been putting a lot of my time in there.
But the the photography 101 posts are still coming!

The following is a photo I took of Tess several years ago.  It remains one of my very favorites.   It was shot in Aperture Priority mode with an f-stop of 5.6.
In order to understand how to shoot in Av mode, one needs an understanding of apertures.  So if you're not quite sure what an f/stop and aperture are and how to pick one, you can go here and here.

Also, if we're going to talk about shooting in Aperture Priority mode, (shortened to "Av" in Canon and "A" in Nikon) it will help to review a wee bit.

Do you remember a long while back when we talked here about the 3 things that photographers can control to get get proper exposure in our photographs?
The 3 things in our camera that control the "exposure triangle" are
1.  ISO
2.  Shutter speed
3.  Aperture
As photographers, we manipulate these 3 things to control the light that comes in our camera.  And it's a fine balancing act between these 3.   If one of these 3 things restricts the light, another must compensate by letting more light in to keep proper exposure.  And visa versa.  If one lets in too much light, another will have to reduce the amount of light it takes in or the exposure will be wrong.

When you hear about photographers shooting in "manual" it simply means that the photographer is setting all 3 of these components, rather than letting the camera automatically set 1 or 2 or all 3 of them.   And when a camera is in Auto mode, the camera automatically set these 3 things.  But there are modes in between auto mode and manual mode where the photographer can set some of these settings and let the camera automatically set the other(s).  Av mode (or Aperture Priority mode) is one way to do this.  By selecting Av mode, the photographer selects the aperture and the camera selects the shutter speed for the best exposure.

Shooting in "Aperture Priority" simply means that the photographer selects the aperture she prefers, and the camera automatically compensates the shutter speed to get the correct exposure.  So in Aperture Priority the photographer has complete control over aperture, she can change it as often as she'd like, but has no control over shutter speed because the camera figures that out and sets it automatically.

Let's get down to the nitty gritty of how to set up your camera to shoot in Av mode.

The first thing to do is to set your ISO.  Ok, you don't really have to set your ISO. You can leave the ISO setting on Auto.  But in my humble opinion, ISO is the easiest of the 3 parts of the exposure triangle to set.  So I do recommend it.

Secondly, turn the "mode dial" to Av.  (If you have a Nikon, it's just "A.")

Third... and this may be the hardest part of all, you will need to figure out what aperture you'd like to pick and set your camera's f-stop.  To determine what f-stop you'd like, you're going to have to think about what you want your image to look like and about the light available.  Do you want a short depth of field?  Or a deep one?  Is it kinda dark, and you will need to let maximum light in your camera?  Be sure to go back to the tutorial on f-stops and apertures if you're just not sure.
This photo of little Miss squirrely pants was shot with a very low f-stop of 1.8. This blurred the bookcase in the background making pretty bokeh.  
Once you've determined what f-stop you'd like, you'll need to select this f-stop/aperture on your camera.
Look at your quick-set screen and look for an F number.  You can then change the aperture by rotating the main dial above the shutter release.

So when might it be a good choice to select Av mode when taking a photograph?
If you're in a dark environment and need to let maximum light in, use Av mode, and set the smallest f-stop to let in the max light possible.
If you are out in bright sunlight and your images are looking over-exposed.  Set to Av mode and select a higher f-stop so less lights comes in your lens.
If you want lots of bokeh, set to Av mode, and select smaller f-stops to get that blurry background.
If you prefer a large depth of field, set to Av mode and select higher f-stops so much of your image is in focus.  You will be limited by the lens on your camera and the f-stops it offers.

In short, to set in Av mode
1)  Set your ISO   (This is optional.)
2)  Turn your mode dial to "Av"
3)  Set your aperture
4)  Shoot

For the over achievers in the group, I know you're out there...
Try this.  Go out and shoot some images in Av mode.  Be sure to shoot images that have small f-stops, and then shoot the same image with a medium f-stop, and then shoot one last time with a large f-stop.  You should notice that your depth of field changes.  But your exposure should remain good, not too light or too dark, because your camera is adjusting your shutter speed accordingly each time you change the aperture.

Holler if you have any questions!


  1. Jumping up and down excited! I received a Canon Rebel for Christmas and am learning my way around it. This post and the ones linked to it are so super helpful. Thanks so much!!

    1. Marci- SOOOO happy about your Xmas present! YIIIPPPPPEEEE! If I can be of any help, don't hesitate to holler. I love to help.

  2. Morning - you did great with this post! It's one of the "eye things" that crime scene photogs "loose" - most everything is shot with a flash and a high fstop so you get as much detail in the image as possible! And you simply skipped over the "amount of light is inversely..." stuff! ;)

    Still - it's the "eye" - and you got that! Me - not so much!

    Oh - and Nikons set the f-stop with the thumb wheel "under" the shutter release - I think very much the same as the Canon!

    hugs - aus and co.

  3. These posts are my fav! Easy to understand and make me (almost) want to go wake up my kids to practice! Think I'll use a doll instead! Thanks for writing this!

  4. Oh quick question. Do you get you camera or lens cleaned ever? I bought mine a few years ago for my cousin so it's a little older. I'm just wondering if that's something I should look into.

    1. Yes, I do. You should use a cloth just for cameras and lenses to occasionally wipe it. There are special "blowers" to clean the glass on the lens. And take your camera in for a professional cleaning if you notice little dots on your photos that aren't there in real life, ones that are in the same place in every photo.

  5. I have a question, I notice when I take pics I have a small dark blemish on each pic. It's always looming near the subjects head. I have looked and see if there was "trash" on the lens, I have wiped and everything. I thought maybe the lens was chipped, but I noticed that the blemish grows/diminish depending on how I zoom in or out. It's quite annoying to get perfect picture but that UGLY smudge has to be cropped our photoshopped out (I don't have PS, I usually have to have my nephew do it on his computer). Any answers?

    1. That's funny that the question above this one is so similar! If it's a spot that is in every pic, in the same place, that's not there in real life, it probably a dust spot inside your camera on the sensor. It will need to be taken in for a professional cleaning. If you have a filter on your lens, check that too to make sure it's clean.

  6. I still have my Kodak Instamatic with flash cubes from the 70s. :)

    1. That's amazing! have fun with it! But can you still buy the flash cubes and film anywhere?

  7. I hope you still respond to these older posts. This is exactly what I was looking for. I just bought a canon rebel and am trying to figure it all out. I love shooting in AV mode but all the sudden my camera will not pick the correct shutter speed. I pick a low f stop and my camera decides to leave the shutter open for seconds. I pick a high f stop and it gets a bit fast but nothing over 1/15 or 1/30 if Im lucky. Any trouble shooting advice? Thanks so much. Great blog with such helpful articles for new photographers

    1. Hi Melanie! Congrats on your new Rebel! I LOVED my first Rebel! I'm going to recommend something that's not the fast easy way but in the long run I do think it's the best way... and that's that even though it sounds like something is "off" on your settings, I do recommend learning to shoot in M mode for just this reason- so that YOU can pick all your settings, and not rely on your camera to do it for you. Ir really sounds like you have a grasp of a lot of what shooting in M is all about already! You get the your f-stop does have something to do with your ss and that they work hand in hand. And that's a BIG step already! Cause ya, 1/30 just is NOT going to be fast enough for a lot of photos!

  8. Can you help me please, I'm new to the dslr's I've searched high and low to find this out but basically I want to photograph my children in av mode to create the blurry backgrounds, every time I shoot them though the image is blurry, I can photograph any object and it comes out not blurry but whenever it comes to the children it always is, the only way I can shoot them is in sports but I brought the dslr so I could shoot them and have the blurry background :(

    1. It sounds like you're having focus issues. And unfortunately there is SO many factors that contribute to sharp focus that it's not a fast or easy answer. My guess is that in aperture priority mode you have no control over your shutter speed, and your camera may be reducing your shutter speed (this is very likely to happen if you are shooting indoors or in other low light settings) so much that the image is blurry. The way to solve this is to 1-shoot in T/S mode so you can control the shutter speed. But unfortunately you won't be able to control the aperture value in this mode. 2-shoot outside or where there's more light. Or 3-learn how to shoot in Manual mode and learn all about the exposure triangle, which may be more that you want to do.


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