Beyond Auto: What the f-stop?!

StudioB Aperture InfoGraphic2

Be honest with yourself:  Are you an Automatic-aholic?  Do you shoot in Auto or P Mode because you have no idea what the other modes on your camera are for?  And by other modes, I’m not referring to the ‘Scene Modes’ that come preprogrammed on some cameras.  Nope, I’m talking about the other other modes on your camera.  You know – the ones you avoid.  The ones that don’t have cute little icons like a flower or running man to help you, but instead are comprised of some weird little alphabet soup of letters like:

A, Av, S, Tv and (*gasp*) M

Sound familiar?  If so, then consider this your intervention.  It’s time to admit you’re addicted to Auto Mode and you don’t know how to stop.  Don’t worry, we’ve all been there.  But now is the time to break free and discover what your camera can really do for you.  Don’t worry we’ll take things slow.  In fact, today we will only discuss the letter A (or Av on some cameras.)  Nothing intimidating about the letter A, right?


The letter A (or sometimes Av) on your camera stands for Aperture Priority.  Put simply, the aperture is the opening in your camera’s lens that lets light in.  It is similar to the pupil of your eye, which contracts and expands in relation to light.  When you have your camera in Auto Mode, the size of this opening is determined by the camera.  However, when you set your camera to Aperture Priority, you as the photographer get to decide how small or wide you want this opening to be.  Why would you care?  Because, from a purely technical standpoint, shooting in Aperture Priority might be the simplest thing you can do to improve your photography. 

Interested?  If so, you must first become familiar with the big ‘F word’ in photography: f-stop.


“Hmmmm”, you may be thinking, “You said we were only going to deal with the letter A, and now you’re throwing another letter into the mix.  What gives?”

No need to worry.  Remember how an aperture expands and contracts like the pupil of the eye?  An f-stop is simply the name given to an aperture’s width.  These various widths are expressed using the letter ‘f’ (for focal length) + a number (for the diameter of the opening.)  For example, you may see aperture expressed on your camera or lens as f/4, f/5.6, f/8, etc.  These f-stop numbers tell you how open the ‘pupil’, or aperture, of your lens is.

Here’s where things get a little confusing.  You see, the whole f-stop numbering system is a bit counter-intuitive.  As it turns out, the wider the aperture (i.e. the bigger the ‘pupil’), the lower the f-stop number, and the smaller the aperture (i.e the smaller the ‘pupil’), the higher the f-stop number.  I know what you’re thinking:  “What genius thought up that numbering system?”  Well, I’m not sure who deserves the credit, but I do know the inverse relationship between f-stops and aperture size is due to mathematical equations dealing with ratios, diameters, halving and doubling and all that other stuff you learned back in high school geometry and quickly forgot.  If you are really into geeky mathematical explanations, you can check out this article.  The rest of us will just accept that the numbering of f-stops is a bit quirky, and move on.


Up to this point you’ve learned that aperture is the opening in your camera’s lens that lets light in.  You’ve also learned that f-stops are how this opening is measured.  As the f-stop number increases, the size of the opening in the camera lens decreases, and vice-versa.  These two concepts can be expressed graphically like so:

F stops

….But why do you need to know any of this?


As I mentioned above, from a technical standpoint, shooting in Aperture Priority might be the simplest thing you can do to improve your photography.  In fact, Aperture Priority should become your new best friend.  Why?  Well, two reasons actually:

1.  Ability to use a faster shutter speed – Let’s go back to the analogy that aperture is like the pupil of your eye.  When it is dark, your pupil (aperture) dilates to let more light into your eye;  When it is bright, your pupil (aperture) constricts to limit the light.  The same is true for the lens of your camera, a wide aperture lets in more light.  A small aperture lets in less light.

Knowing this is helpful when you are hand-holding your camera in low light situations and you want to freeze the action to reduce image blur.  By setting your camera to Aperture Priority and choosing a wide aperture (i.e. low f-stop number), your camera will automatically grab the fastest shutter speed available given the current lighting situation.  When you combine a wide aperture with a fast shutter speed, you reduce the possibility of motion blur.  I’ll delve into shutter speeds more in a future post, but for now just remember this formula:

Wide Aperture (low f-stop) + Fast Shutter Speed = Less Motion Blur

2.  Control over Depth of Field – Depth of field (DOF) is the range of focus in front of and behind the object you are focusing on.  In other words, DOF is the measurement of how much of the foreground and background of a picture is in focus.  Manipulating DOF gives you creative control over the final image.  A shallow DOF is perfect for isolating your subject from the background.  A deep DOF is ideal for achieving equal focus among the fore-, mid- and backgrounds.  Having control over DOF is the #1 reason that Aperture Priority is my favorite setting on my camera.


All of this technical information is just fine and dandy, but what you really want to know is how you can use Aperture Priority to improve your photography.  Let me share with you a few rules of thumb that I have discovered in my own photography practice that will help you determine which f-stop to choose in various shooting situations:

Portraits and Macros – Portraits and Macros generally look best with a shallow DOF, which allows you to isolate your subject from the background.  To achieve this, you would set your lens to a wide aperture, or low f-stop (f/5.6 or lower).  The images below demonstrate just how effective a shallow DOF can be:

Studio B Photography Denver


Imagine if the images above had been photographed using a deep DOF, where everything in the frame was in focus.  The results would have been too busy, and the subject matters would’ve been lost in the mayhem.  You will find that using a shallow DOF (low f-stop) is particularly useful when shooting subjects against a busy or unappealing background.

Groups of People or Objects – Groups of people or objects work well with a mid-range DOF, or mid-range f-stop (between f/5.6 and f/11).  By shooting with a mid-range f-stop you will have a subtle pop of your subject against the fore- and backgrounds, but will still maintain enough DOF to ensure the key subjects are in focus.  Check out these examples:

Studio B Photography Denver


Compare the images above to the previous portrait and macro images that used lower f-stops.  See the difference?  Note how the mid-range aperture provided enough depth of field to ensure that the primary subjects are in focus.

Extra Tip:  A mid-range f-stop is also a good ‘default’ in difficult shooting situations, when you are unsure where to set your f-stop.

Landscapes – Landscapes lend themselves well to a deep DOF, or high f-stop (f/11 or higher).  Deep depths of field are excellent for communicating scale, especially when paired with a wide angle lens:


In the image above, notice how virtually everything is focus – from the oarsman in the foreground, to the passengers in the mid-ground, and even the cliffs in the distant background.  This depth of field is achieved by using a higher f-stop.

Low Light Situations –  As I mentioned above, when hand-holding a camera in low light situations, it is best to shoot with a wide aperture to allow your camera to use the fastest shutter speed available in the situation.  In the image below, I captured my son flaunting some car keys on the first day he had his driver’s license.  Because I wanted the emphasis of the photo to be on the keys, I decided to shoot this image in a dark room with a single light source directed at the keys.  By choosing Aperture Priority set to a wide aperture (f-stop of 5.6), the shutter speed selected by the camera (1/60th) was fast enough to disguise any motion blur that may have arisen from either my hands shaking while holding the camera, or my son’s hand shaking while holding the keys:

License to Drive

(Note:  If you are very astute, you may have noticed that the ISO setting on the image above is 500, whereas it was 200 in the other photos.  This is because, ISO is another factor that comes into play in order to achieve proper exposure, especially in low light situations.  Since I don’t want to complicate today’s post any more than necessary, we’ll discuss ISOs and their effect on exposure in a future post on shutter speeds.  For now, just set your camera to ‘ISO Auto’, which is the default setting on most cameras.)

Exceptions to the ‘Rules’ – Of course rules are meant to be broken, so feel free to play around and find out what apertures give you the artistic edge you are looking for.  Sometimes your experiments will work, sometimes not.  But with the ‘free film’ of today’s digital cameras, what do you have to lose?  Below is just one example where I purposely defied my own ‘rules of thumb’ when photographing a group of cyclists.  Instead of choosing a mid-range f-stop, which I typically would do when photographing a group, I instead chose a low f-stop (shallow DOF) in order to make the lead cyclist (Cadel Evans!) stand out from the peleton.  I think the result is quite effective:

Cadel Evans Pro Cycling


Do not fret trying to memorize any of the technical concepts I’ve presented in this post.  I’ve included below a little ‘cheat sheet’ that you can carry around in your camera bag as an easy reference guide.  Once you get out there and start shooting in Aperture Priority, you will find these concepts become second nature to you.

The first step in breaking free from the confines of Auto Mode, is diving into the world of Aperture Priority.  This is your chance to make your camera work for you.  Your camera is merely a tool to let you express your creativity – but you need to tell your camera what to do.  Learn to be your camera’s master, not its slave.

Most of all, remember that photography should be fun.  Allow yourself to take risks, make mistakes, and explore new and different ways of capturing life through the lens.

Happy Clicking Everyone!

Aperture InfographicFor simplicity, the graphic above shows ‘whole’ f-stops that are available on most cameras.  Higher-end models have the ability to shoot in 1/2 or 1/3 stops (e.g. f/2.8, f/3.2, f/3.5, etc), which gives you even more control over your images – a cool feature, but don’t worry if your camera doesn’t offer these.  Remember, in the end Cameras Don’t Matter, but photographers do!

2 thoughts on “Beyond Auto: What the f-stop?!

  1. Pingback: Are you an Automatic-aholic? | Beth Poe :: Photography

  2. Pingback: Beyond Auto: Full Speed Ahead | Eyes Like A Shutter / Mind Like A Lens

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