In trying to determine what the next blog tutorial should be about, I was really having trouble. The problem was I kept thinking in terms of chronology - what would people best need to know after reading the last tutorial? But now I've come to the conclusion that I will just share whatever is in my head asking to come out when I sit down to write - today that thing is a photographic concept known as 'Depth of Field'. The term 'depth of field' or DoF for short should be well known to anyone who's been shooting for a while but though it's not a TERRIBLY complicated concept to grasp, I find that some of my friends and peers occasionally struggle with the application and control of DOF, which is a shame because it's a factor that has the ability to dramatically transform a photo! So for the uninitiated, the next question I guess must be WHAT THE HECK IS DoF ANYWAY?? In basic terms, DoF can be defined as the amount of an image that is within 'acceptable focus'. I make every effort to write these tutorials in such a way that people with many different levels of photography skill can gain something from them, so without being terribly technical this description should suffice - I'm guessing no one reading this wants to hear me get into discussions of the 'Circle of Confusion' or lens mathematics! With all that said, the next questions must surely be WHAT DO YOU MEAN BY 'ACCEPTABLE FOCUS'? and HOW CAN I CONTROL THE DoF?? I'm glad you asked! First of all let me explain acceptable focus - this is a discussion that could go on for a while actually, so I will try to bake it down to the bare essentials for the sake of all our sanity. Strictly speaking, in any given photo there can only be ONE point which is properly focused and everything else is either in front of or behind that focus point. To the naked eye however the distinction between in and out of focus is not always so readily apparent, as an image shot with a large DoF will have more elements that 'appear' to be in focus from foreground to background, while an image shot with a very small DoF will have only a small portion of the overall image in focus. Controlling the DoF in your photos is yet another topic where the discussion could go on and on, but for simplicity's sake allow me to simplify it for you, oh faithful reader :). The primary methods for controlling DoF that you should be concerned about are lens aperture and subject-to-camera distance. Lens aperture refers to the size of the opening in your camera's lens through which the light enters to expose your photo. The smaller the opening, the greater the DoF, the larger the opening, the smaller the DoF. Before moving on, please go back to the previous sentence 3 times and read it out loud. No, really. Go back and read it... Yes, OUT LOUD! :) Ok, so here's where it gets a little tricky for some people because controlling the aperture setting on your lens means setting a number which is basically the inverse of what I just said. What I mean by that is, a lens aperture of f/2.8 - a small number - is actually a LARGER opening (meaning lets in more light and causes a shallower depth of field) than an aperture of f/16 for instance. BTW controlling the aperture generally requires setting your camera to manual (or aperture priority), otherwise your camera will decide for you what the aperture should be...where's the creativity in that? How would your camera know what you're trying to do anyway? Aren't you reading this because you want to start taking better photos and stop taking snapshots?? Be forewarned - we're going to slowly wean you off of the automatic stuff around here... The second method of controlling DoF is 'subject-to-camera distance', this is not terribly technical and requires no fumbling around with your camera manual at all, its just like it sounds - move closer and get shallower DoF, move farther away and get a larger DoF. So here are a couple of examples of shallow vs. large DoF in application, in this first photo the aperture used is f/1.2, which is the largest aperture available in 35mm lenses today. Notice how the potentially distracting background foliage turns into a rather pleasing blur (this blurred background is known as 'bokeh') and makes the subject stand out in the photo.
In contrast, the group photo below would suffer from a shallow DoF as some of the individuals would be difficult to identify, so clearly a much smaller aperture than f/1.2 is called for to provide the greater DoF. In this case I chose an aperture of f/9 and a longer subject-to-camera distance to render all the faces within 'acceptable focus'.
This is just meant to be a primer, something to get folks out there to take off the training wheels that are the automatic camera settings and play around with being more creative and deliberate with their photos. There are lots of things omitted here, most of which I intend to address in future editions of our tutorial series but for any of our faithful readers who would like to continue the discussion or have questions that just can't wait, I am always available to share what I know - just contact me via email anytime. In the meantime, keep shooting people!
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