Isolated Sharpness

Tips and techniques for using shallow depth of field to add impact to your macro shots

1 Keeping your depth of field to a minimum is particularly useful in close-up photography where small plants and insects can be made to jump out from a cluttered background. Sheppard made a monochromatic image by letting the background become a yellowish swath of color. The backlit yellow flowers stand out.

When shooting close-up and macro images, you quickly discover that depth of field is narrow regardless of what you do. This is because depth of field is strongly affected by your distance to the subject—the closer you get, the less depth of field you have. This can frustrate photographers because they think there’s always a need to have more sharpness in the picture, more depth of field.

Sometimes, though, that’s counterproductive to what you’re trying to do with your photo. The struggle to get more depth of field may end up giving you enough extra sharpness that a background, which could have been a simple swath of color, instead becomes a distraction. Going for maximum depth of field isn’t the default “best” way of shooting.


2 Limiting depth of field isn’t just for the background. You can see on the right side of this photograph that some lupine close to the camera in the foreground have been blurred to create a colorful zone that draws the eye to the sharp flowers behind it.

Shallow Depth Of Field
Shallow depth of field does something for a photograph very similar to the way we see the world. When we focus in on a subject, our brain cuts out detail to most everything else in our field of view. The camera doesn’t do that, however, so how do we translate the way we see a subject to how the camera records the same thing? With shallow depth of field, the subject can be rendered tack-sharp, but everything in front of or behind that subject is kept soft. That contrast in sharpness makes the subject stand out. This mimics the way that we see.

• Here’s a list of possible reasons why I use shallow or selective depth of field when I shoot:
• Highlight my subject
• Make the background a soft blend of color
• Define a composition
• Isolate my subject
• Change colors (in-focus and out-of-focus colors look very different)
• Create a more striking look for an image
• Create selective-focus effects (when I have out-of-focus objects surrounding an in-focus subject)

The contrast of sharpness you get with shallow depth of field is one of the classic photographic techniques for defining an image. By defining an image, I mean that you’re doing things in your craft as a photographer to help guide the viewer through your photograph. Sharpness contrast allows you to clearly define where the main subject is and where it is not.


3 The single stalk of golden grass would have been lost in a sea of other stalks if Sheppard hadn’t used such a wide-open ƒ-stop.

Creating Shallow Depth Of Field
Shallow depth of field starts when you choose a wide aperture for your lens. Often, it helps to set your lens at its widest (maximum) aperture, such as ƒ/2.8 or ƒ/4, or at most, stopped down one stop from that maximum. This gives the least amount of depth of field for a given distance and focal length of lens. Avoid the middle ƒ-stops of ƒ/8 or ƒ/11 for this effect (with some lenses, one stop down from maximum may be ƒ/5.6, which is okay, but borders on the middle apertures).

Focal length has an effect on depth of field. A wide-angle lens gives more apparent depth of field than a telephoto. If you combine a telephoto lens with a wide ƒ-stop, you get even more limited depth of field for a stronger effect. Then if you close in on a subject with a telephoto set to a wide ƒ-stop, you get a very narrow depth of field.

With wide-angle lenses, it’s harder to get shallow depth of field because, even at maximum aperture, the lens gives more depth of field than a normal or telephoto lens at a similar ƒ-stop. The shorter the focal length of the lens, the more depth of field, e.g., 20mm has more depth of field than 50mm. This means that if you use a full-35mm-frame format compared to an APS-C or Four Thirds format, you use a longer focal length for any given angle of view. (For example, a 105mm lens on a full-35mm-frame-format camera gives you an equivalent angle of view and framing of 70mm on an APS-C-format camera.) The result is that a full-35mm-frame-format camera consistently gives you less depth of field.


In these diagrams, you can see how the depth of field changes with the aperture setting. With any ƒ-stop, there will be a plane of absolute, sharpest focus. On the other side of that plane is the zone of acceptable sharpness, which we call depth of field. With a bigger aperture (and smaller ƒ-stop number), the zone of acceptable sharpness is narrow. A smaller aperture (larger ƒ-stop number) gives you more depth of field.

That may be a discussion point for a camera club, but it can affect how you photograph. If you shoot with a smaller format, you get increased depth of field with a given angle of view or framing of your subject because you’re using a shorter focal length. That can be great if you want depth of field. On the other hand, it can be a challenge to get really shallow depth of field with the smallest formats, such as Four Thirds, Micro Four Thirds or with a compact camera like the Canon PowerShot G11. With these cameras, you need to get close to your subject, use longer telephoto focal lengths and use the widest ƒ-stop possible.

Background Distance

The distance to the background behind your subject is an important part of using a shallow depth of field, yet it’s something that’s often missed. The distance to the background is a different thing than the distance to your subject. It’s easy to pay attention to the distance to the subject and not notice how close or how far the background is behind the subject. The closer the background, the more it is in focus; conversely, the farther the background, the more out of focus it becomes.

For example, many people photograph flowers from above the plants. Imagine doing that and think about how close the background is behind the flowers. Next, think about getting lower so that you shoot the flowers from at about their level. How close is the background now? Often, when you get lower like this, the background suddenly gets very far away compared to the ground when you shoot down on photographs. That distance affects how sharp the background is, especially when you’re using larger ƒ-stops.

Look at your subject. When you’re up close, often you can move a slight distance up or down, left or right, and change what the background looks like simply because you found an angle that puts the background farther away. Having a more distant background frequently gives you nice, soft tonalities and colors.


4

5
When experimenting with selective focus, think about the colors in the background. By making that background go very soft, you can create interesting color compositions like these two images. While the main subject is the same, image 4 is a color-opposite color composition, and image 5 is a monochrome color composition.

Challenges With Shallow Depth Of Field
Focus carefully. Depth of field is narrow when you’re doing close-up and macro work anyway, and with the shallow techniques described here, you’re guaranteeing an always narrow band of sharpness. Choose where that sharpness is very carefully.

This often means using manual focus. Autofocus frequently puts your depth of field at random places when you’re up close. You may think it looks okay in the LCD review, but unless you magnify that image (and I often do), you can be fooled. It’s frustrating to look at your photos on the computer later and discover that focus is on the wrong part of a flower or the hind end of a bug instead of its eyes.

You can use autofocus up close for the effects seen on these pages, but you need to lock focus and not allow the autofocus to continuously find new points to focus on. Most cameras lock focus by a half push of the shutter release. Some have special buttons on the back of the camera that you can use. Lock focus, then if focus is a little off, move the camera closer or farther from the subject to refine focus. That’s also a good way to work with manual focus.

Since you’re shooting with a large aperture, you’re usually using a faster shutter speed and don’t necessarily need a tripod. Since focus point is so critical, I find that using a shallow depth-of-field technique is difficult when using a tripod, so I usually don’t. I need to move, often even moving with a blowing subject.

Look for distractions along the edges. The shallow depth of field effect can be so strong and so overpowering as you look through the viewfinder or on the LCD that you miss something important—sharp distractions around the edge of the image that can fight with your sharp subject. Be careful of what’s sharp in your photo besides your subject. Look at those edges and be sure you haven’t inadvertently included something sharp that shouldn’t be sharp. You may have to check your LCD review to be sure the edges aren’t a problem.

Anytime of year is a great time to experiment with this technique. I’ve used shallow depth of field over the years for everything from snow crystals to dew. I have to admit, though, that my favorite subject for this approach to photography is a flower. That’s when you can especially play with all sorts of in- and out-of-focus colors and tonalities.

Extension Tubes And Limited Depth of Field
An easy and inexpensive way to get quality close-up and macro images is to shoot with extension tubes. Extension tubes are simply tubes that fit between your lens and camera body, and have no optics in them, only connections for the lens electronics. With them, any lens will focus closer—how much depends on the thickness of the extension tube and the focal length of the lens.

They also work great for getting shallow depth of field. They don’t cause the shallow depth of field, but they do allow you to use any telephoto as a “macro” lens (including zooms). Using a telephoto up close will give you shallower depth of field because telephoto focal lengths have inherently less depth of field and getting closer to the subject gives less depth of field. (Wide-angle lenses often won’t work with extension tubes.)

Being able to use a telephoto up close is a great benefit because it increases your options as a photographer. With extension tubes, you’re not limited to the focal lengths available in macro lenses. Plus, adding extension tubes to your bag takes little space and weight, and costs you a lot less. ABOVE: Kenko DG extension tubes

Rob Sheppard’s new instructional videos on Lightroom and more are available at www.robsheppardphoto.com.

13 Comments

    Not only sharpness, but background saturation, brightness, and contrast are just as important. All of these factors can be better managed with software. Choose your best aperture and then doctor your background.

    Another useful piece of advice that got passed over in this article is the importance of being attentive to the sensor plane (or ‘film plane’). When using a very shallow depth-of-field, it can be very beneficial to consciously think of what aspects of your subject are positioned perpendicular to the direction of your camera. This allows you to more exactly utilize the limited depth-of-field available with wide apertures or macro lenses. For instance, this technique can be used to more precisely isolate two or three stems in a stand of wildflowers. It can also be used to produce the sharpest results when photographing relatively flat wildflowers head-on… by aiming your camera perpendicular to the direction that the flower faces, you ensure that each and every petal is sharply resolved and prevent any portion of the flower from falling outside the focus range.

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