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Tips for Using Your Camera Creatively by Jon Sienkiewicz, April 2009 (updated June 2010)
Introduction | I: ISO Setting | II: Program AE | III: Aperture & Shutter Priority | IV: White Balance | V: Depth of Field | VI: Bracketing | VII: Megapixels | VIII: Flash Modes
The Missing Pages column is a collection of all of the information that should have been included in your camera’s Owner’s Manual—but somehow got left out. This is a hybrid assortment of short articles that delivers the know-how you need to derive the maximum enjoyment—and creative expression—from your equipment.
It’s sort of a juiced-up User Guide for creative people who are not necessarily technical. Each part will teach you how to use one of the camera features or functions that you previously ignored or left set on Auto. And each will include a Creative Project so that you can try some scripted experimentation.
We will explain complex technical subject matter a way that everyone can understand. And if you happen to be a technical expert yourself, we’re including “Nerds Only” sidebars just for you. That way you can dig in deep—or just straddle the edges—of the technological stuff. It’s your decision.
You’ve seen the classic portrait that depicts a smiling face in sharp focus floating over a blurred and obscured background, as in the photo below. The subject appears to pop right off the page. And you’ve seen hundreds of shots of landscapes where the animals in the foreground are as sharp and clear as the mountains behind them. How can you control exactly what’s in focus and what’s not—particularly with an autofocus camera?
The phenomenon at work here is called Depth of Field (DOF). Because it’s predictable, reproducible and measurable we can use it to our best advantage. And since it’s been studied by scientists and optical engineers for centuries, we know a lot about it.
DOF increases as the diameter of the aperture decreases; in other words, a smaller f/stop (like f/16) generates greater DOF than a larger f/stop (like f/2.8). Sometimes people confuse this with sharpness but the two are quite different. In fact, using a very small aperture can rob you of sharpness. You can learn more about that by reading the Nerd’s Only section below.
One way to control DOF is by using the right aperture, the aperture that delivers the amount of DOF that you’re after. Shooting in Program or Auto Exposure mode surrenders control over the f/stop, so your camera must be set on Aperture Priority or Manual if you wish to control DOF. Some lenses have a Depth of Field scale printed on the barrel. It looks like a symmetrical set of hash marks that delineate the range of focus when aligned with the aperture that’s being used and the distance from the subject.
This is a very reliable way of determining DOF. Unfortunately, it is accurate without being precise. The increments are simply too inexact. As you can see in the image above, this particular scale skips from 1 meter to 1.5 meters to 3 meters to infinity. And you won’t find a scale on a zoom lens since the focal length is literally a moving target.
Optical engineers have created DOF charts for many different lenses. Many high quality lenses include these charts in the owner’s manual. DOF can be calculated mathematically using the circle of confusion for a given lens as one of the variables. The term “circle of confusion” describes a spot of light that is slightly out of focus when a lens is focused on a given point. You do not need to know anything about circle of confusion to control DOF.
Some digital SLR cameras have a DOF preview button. Even if your camera does have one, don’t trust it 100%. The DOF that your eye perceives when looking through the viewfinder differs from what the camera sees, even when the lens is stopped-down to the shooting aperture. It’s a close approximation, but not identical. Use a DOF chart or the scale described above.
Wide angle lenses produce more DOF than telephoto lenses (assuming that film format or sensor size is the same). Some will argue that if you crop a WA image to match the field-of-view of a telephoto lens the DOF will commensurately diminish. So what? The point remains: put a wideangle lens on your camera and you’ll enjoy more Depth of Field.
Depth of Field always extends 1/3 in front of and 2/3s behind the point of focus. No matter whether the DOF is deep or shallow, it always follows this formula. This fact becomes more valuable when you do macro photography.
Depth of Field decreases as the distance between the subject and film plane decreases. You have VERY little DOF to work with when doing macro photography and are focused just a couple centimeters away, but you have extreme DOF when focused at a point near infinity.
All lenses have a Hyperfocal Distance for a given f/stop. If, for example, the Hyperfocal Distance happens to be 16 feet for a particular lens/aperture combination, everything from one-half that distance (8 feet) to infinity appears to be in focus. If your lens has a DOF scale as described above, line up the infinity symbol with the f/stop you are using and you have just set your lens to its Hyperfocal Distance for that f/stop.
Depth of Field sounds like a good thing and usually it is—but not always. If you want to produce dramatic portraits you’ll want to limit DOF, as in the image at the top of this story. By limiting DOF you can make a lens appear sharper. Can you guess why?
Claudio Di Martino , September 11, 2009; 07:52 A.M.
Leo Jonkers , September 14, 2010; 07:04 P.M.
Laurentiu Cristofor , September 26, 2010; 07:51 A.M.
