Hello Monday students!  Today is the second Monday Lesson.  Today I am going to talk about Aperture or F-Stop and what it can do to make your photographs better.

I get asked all the time about what the various letters and icons are on people's cameras.  You have the flower, the running man, the mountain, AV, TV, S, P, A... What the heck does all that mean?!  I won't be able to address them all but I am going to pick off the ones that have the most to do with today's' topic- aperture.

OK, so if you have a Canon camera like I do, you may have the letter combo AV somewhere on your dial.  For Nikon Users, you may have an A.  If you do not have any of the letters but only icons, it's a little tricky.  You may need to consult your manual.  However, on many cameras the icon we are talking about today is the "portrait" mode or the one that looks like a face.

So, before we start using our cameras, let's define Aperture and talk about why it is a tool you need to know about.  The aperture is a hole or opening that light passes through.  The greater the size of the hole, the more light comes in to the camera and the smaller the hole the less light.  Here is a picture I found on Wikipedia that shows a large and small aperture inside of a camera lens.



I think it is helpful to think about your own eyes.  Your pupil is like the aperture ring of your eye.  When the room is dark and your eyes need more light to see your pupil dilates allowing the maximum amount of light in.  When you go outside, and it is bright, your pupil gets smaller.

Other than controlling how much light comes in through your camera lens and strikes the film (or digital sensor), your aperture (also called F-stop) controls something called depth-of-field. The depth-of-field (DOF) is the distance in front of and beyond the subject that appears to be in focus.  Think of it as depth of focus.  When you focus your camera, you select a spot to be in focus.  By adjusting your aperture, you can control how much is in focus behind and in front of your chosen spot of focus.  

Here's an example.  My son's toys have volunteered to act as models.  Here are two images of Optimus Prime and his sidekick T-Rex.  In one you see the background is in focus and in the other it is out of focus.

(First image is F 1.8 and the second is F 22)

Big difference right?  Let me explain a little bit further.  The aperture openings in the lens are identified by a number.  The numbers start around 1.4 and go up to about 22 (depending on your equipment).  We will get to where these numbers are in a moment.  The low numbers mean that the opening in the lens is at its largest and the high numbers mean the opening is the smallest.  I know that seems a little opposite but it is just the way it is.

So, what do the numbers mean and how do they control the DOF?  If your camera is set to a wide-open F-stop (a low number) then the areas in front of and behind your point of focus will be blurred or softly focused.  If your camera is set to a small F-stop (high number) then your background and foreground will be more in focus.

Don't glaze over yet!  Now I need to tell you why this is important and how to use it.

All pictures tell a story.  The better the picture, the better and more impactful the story can be.  Let's get back to Optimus and T-Rex...If I wanted to tell a story about Optimus Prime having a battle with T-Rex and it was important that the viewer see where the battle was taking place then I would want my background to be in focus.  However, if I didn't want anyone to see the trash can and rake in the background then maybe I would want my background to be out of focus.

(first image F 1.8 and the second F 22)

Another example, If I wanted to take a portrait of this lovely couple and I wanted the viewer to really focus on the faces (and dare I say, the relationship between them) and not on the distracting background elements behind them (the power washer), then I would also want the background to be out of focus, like this:

(first image F 3.2 and second F 22)

So, the best news of the day is that it is really pretty simple to control this!  OK, so how?  When you set your camera to aperture priority mode (AV or A) you will be able to change the F-stop number to whatever you like and the camera will figure out the rest of the exposure. 

Obviously there will be certain circumstances where there is not enough light or even too much light to get exactly what you are hoping for.  One problem that you may run into is that a small aperture opening (big number) may end up making your shutter speed get really slow.  This can cause your image to be blurry all over.  If that happens it is because you just don't have enough light to use such a small aperture opening.  The opposite problem would be that there is so much light that your big wide open aperture (small number) is giving too much light and your picture looks too bright and over exposed.  My suggestion would be to look back over the First Monday Lesson about Open Shade, grab a transformer (or something else that will sit still) and go experiment with your F-stops in an open shade setting.

You do not want to use flash while experimenting with this project!  It will change the look of things and make it all more complicated.

You will need to experiment because at the widest f-stops (like 1.4, 1.8, 2) your DOF can be so shallow that someone turned at a ¾ angle to you may have one eye in focus and the other slightly out of focus (notice in picture 1 the tip of Optimus gun is out of focus).  If you really want to get a feel for the differences between the stops I would set up a scene and take a picture at every F-stop (making notes so you can remember what you did).  Here's an example of three different F-stops in one scene.  Many thanks to my lovely models.

(top image F 1.8, middle F 5.6 and bottom F 13)

So, now it is time for you to go out and practice.  The best situation to practice in is one where there is ample light (not indoors or at night but not in direct sun either) and one where you can easily manipulate a single subject (i.e. Optimus Prime).  I would not recommend trying this out on your 18 month old who does not sit still.

I would love to hear your comments and see your experiments.  Please let me know if you found this helpful (or if it was too confusing).  Your feedback will help me refine and make The Monday Lesson better.

A few notes- Normally I would remove things like the rake and the power washer or frame them out somehow but, for the purposes of this experiment, I wanted to show you how to deal with items like these if you cannot move them.  Also, I did not use any additional light like a flash and the images are straight out of my camera with no retouching or other enhancements.  I shot these using my Canon EOS 5D and an 85 mm lens.