By design, this post of photo knowledge will stay short. The Depth of Field (DOF) can get complex but for now, we have some simple tools that help to previsualize the image you’re creating. There are numerous things that affect the depth of field (DOF) and there is a mechanism and numbers on the lens of some cameras that mean something but the core of what you need to know is what is in large type just a ways down this article. Remember that! You know that the aperture produces images with massive depth of field (Sharpness) and the aperture, set differently, can make the depth of field very tight. The very minimal sharpness and blur to make a dreamy background is a nice look for portraiture, macro, and some commercial photography. Super sharp can also be a look for some subject matter.
But in a given situation like the shot here of Steven Monismith, once the lens is chosen and the composition is locked and any other options are covered we have today’s RULE to draw comfort it. If the aperture is a small number then the depth of field is small (less is sharp) and if the aperture is a large number the depth of field is large (more is sharp).
Nikon D7200 at f5.6 for 1/1250th at ISO 400. Nikon 80-200mm 2.8.
If the f-number is Small then the Depth of Field is Small. If the f-number is Large then the Depth of Field is Large.
For those of you with experience, you may have heard about this rule before. Most have heard a variation. There are things about the extra details in that other rule that make it difficult to remember. This rule covers what a new photography enthusiast needs without clouding it with less important details. This will hopefully help in decision making through the early months and years of one’s photo journey. As progress is made in your photography you will easily add to this rule. At that point, you’ll realize why I’ve trimmed away some less than necessary info. If you must know, reach me at @OfficialTEKeez.
Varying Amounts of Blur
How does that affect our real-world situation? The illustration shows Stephan with background buildings over 100 yards away. Based on our rule the background could not be sharp at any possible setting of the lens. So, the thing that we control and an extension of our rule is “how” sharp the background is displayed. Our photograph is shot at f5.6. With that, we can tell what the background is but that it has the dreamy look of a painting. At f2.8 the dreaminess may have been overdone and we would not pick up on the urban feel the shot has expressed.
Control The Blur
If we moved to an aperture indicated by a larger number, we would have a sharper background (Larger DOF). If we wanted a more blurry, dreamy background a smaller number would have been used (Small DOF). You may shoot similar things over and over. Some of these distances and effects of the depth of field may become something you can draw from in regular repeatable work. Many in portraiture work with only a few of the f-stop settings. So, they get very familiar with the amount of softness found in their backgrounds. For the rest of us, we’ll use the exposure viewing on the camera back. Check and tweak the results with the next exposure.
Try pressing the depth of field preview. It’s commonly found on the camera body somewhere near the right middle finger. By pressing while composing, the lens will close down to the aperture you’ve selected for the exposure. You’ll see the depth of field as it will appear in that finished photo. For DSLR shooters this display will darken. The shooting aperture is closed down and allows less light into view. Try to ignore the darkness and notice how certain areas will sharpen up as it displays at the shooting aperture. It may be different for some mirrorless shooters. The darkness will be corrected digitally to keep the brightness equal to before pressing the button. But notice the visible sharpness as it changes. It’s a nice feature. To really see the use of this preview, step into a sunny situation and set the f-stop at f16 or f22 and press. Look for the sharpness. The difference could be extreme and a background super blurry could become near sharp viewing at f16. BTW, if you don’t think you have the preview button, check your manual.
Small Number = Small DOF Large Number = Large DOF
Try it, frame a photo just around your home, pick an f-stop in the middle (5.6, 8 or 11) and after focusing, press the preview. Added sharpness should be visible through the darker view. Wide open (smallest f-number) is the way you normally view thru your camera, viewing is always through an aperture wide open, so anything change you make to close down, even slightly, will have an increase in visible sharpness or DOF.
Depending on the lenses you have, you may have a depth of field scale. It was a common feature of older 35mm and 120 medium format lenses. Not common anymore. It was a way to clearly determine the range of sharpness or your DOF. You focus on your subject and determine the f-stop you’ll use for your shot and check the scale on top of the lens. You can easily determine the distance to your subject.
For our example, let’s say subject is 10 feet away. On the 50mm lens at f8 we can see, on that extra scale, that acceptable sharpness will start approximately 8 feet and extend to 14 feet from the camera. That is six feet of Depth of Field. Some lenses have color coded depth of field scales. Meaning that the f-stop numbers are in color with small marks in the same color indicating where they intersect the distance scale. My f8 is red and there are red marks interacting with the distance scale. Those are the marks indicating the area of sharpness, from 8 to 14 feet in our example.
Learn this now and be ready when the mirrorless camera takes over the world (Oh No). I checked the Fuji X-Pro2 (Awesome and small camera) and it has a visual representation on the rear LCD screen much like the analog scale discussed here (Also I rented a Sony awhile back and it too had the display). That visual aid, whether it’s analog or digital is a clear and understandable tool for the advancing photographer.
Kids are moving or being still. It doesn't matter. Capturing those special moments are a motivation for mastering the camera. The softness in the background and foreground can draw the attention to the eyes. Composition is enhanced by working with the DOF. Nikon D750 with Nikon 80-200mm f2.8
I will be passing along numerous things about composition and the rules, or suggestions (haha), that go with organizing the elements of your photo. At the core, we are challenged to take the width and height of our photo and as much as possible extend our vision to three dimensions. Giving an image depth with our two-dimensional constraints. We use shadow and highlights and so many things; but do not forget this subject, depth of field. The dialing DOF in just right as another tool of the composition. Think of a favorite photo and relate to the fact that the super blurry to subtly blurry background and possibly foreground was not just arbitrary. It is planned. The more you know and can pre-visualize the sharpness or lack thereof of your photos; the more you’ll add to the impact and storytelling ability of your imagery. The viewer’s eye travels around the image. It’s attracted to light before dark and sharp more than non-sharp. Happy Shooting.