What Is Sharpness?

A Deeper Understanding Of Sharpness Can Help Better Control It
What Is Sharpness? Sharpness is a critical issue for photographers. While we sometimes experiment with blurs, we mostly want our subjects to be as sharp as possible. The standard, reliable approach is to use a good lens and tripod.

You've heard that line before, and if you've been a longtime reader of Outdoor Photographer, you know how important a tripod is to getting the most from your gear. Quality lenses are very affordable today, so there's simply no excuse for unsharp photos

Let's delve a little deeper into sharpness, examining a number of issues that affect it, whether you shoot film or digital. Better understanding the issue can help you get the most from your camera and lenses.

Image Brilliance
A few years ago, you truly could see a difference in photographs shot with certain lenses. They had a crispness and brilliance that set them apart from others. The effect looked a bit like sharpness, yet a lens could have high resolution and low brilliance. For example, about 30 years ago, higher resolution and low brilliance could be found in some of the independent brands like Soligor. High image brilliance was particularly noticeable in Nikon and Leica lenses. Part of this came from a lens' ability to hold highlights.

This is no longer true. Modern computer-aided design and construction, low-dispersion glass elements, APO designs and other optical technologies have given every lens manufacturer the tools to make high-quality lenses with high image brilliance. The result is much sharper-looking images, regardless of the way a lens deals with a resolution chart. Even budget lenses have a level of brilliance that couldn't be reached at their cost 20 years ago.

Buying a quality lens isn't enough, however. Photographer John Shaw once told me of a workshop attendee who complained about the poor image quality of his Leica lens. John noticed the gentleman's technique—he never used a tripod. Leica lenses tend to be quite heavy, so this made it difficult to get the quality that had been built into this lens. John wanted to offer to take that"crappy" lens off the photographer's hands.


Most photographers think a tripod is used to prevent blurry photos, and to a degree, it is. It also ensures that the image brilliance inherent in a lens is captured. Sharpness can be lost with cheap, too-light tripods, however. They can shift enough during exposure so that while the photo stays reasonably sharp, image brilliance suffers. A quality, rigid tripod and head is critical to ensure you capture the image brilliance and sharpness of which your lenses are capable.

Contrast
If you put a solid black line on a white paper, it will appear very sharp. If you use a light gray line, it won't look as sharp, and you may find yourself struggling to focus on it if your eyes are much beyond 30 years old.

Contrast has a significant affect on apparent sharpness. If your subject contrasts strongly with its surroundings, it will be seen by the viewer as sharp. This is one reason why backlit photos often look so sharp—bright contrasts appear between the light and shadow in those conditions. It also explains why foggy photos don't look as sharp—subtle grays have little contrast.

Look for contrasts in your composition wherever appropriate. You could move slightly one way or another to allow a dark area to line up with a key light part of your subject, just for the contrast. Or you could look for contrast in a scene that could be included in a composition.

Light
Have you ever noticed how images of Western mountains and deserts often look sharper than East Coast forests? This is due in part to the light. There typically are fewer clouds in the dry areas of the West, plus there aren't as many trees blocking the sky. This allows clear, crisp light to skim rocks and other geological features, bringing out texture and form, which makes a landscape look sharper.

In addition, with fewer clouds and less humidity, the clear light has more of an edge to it, making it more specular and more contrasty (including color contrast from shadow to light) and heightening the look of sharpness. This certainly can happen anywhere with the right conditions, but haze is more common east of the Rocky Mountains, making this effect on sharpness harder to manage there.

Anytime light can be used to increase contrast, apparent sharpness will increase. While you can't control the weather, you can change your angle to the subject. Sidelight and backlight always give more contrast than light that strikes the front of the subject. Low light also tends to increase contrast, which is another reason why shooting landscapes with the sun near the horizon is such an effective technique.

Flare
Backlight is a great light for sharpness, but it has its own challenges. As light strikes the lens, flare often appears. Specular flare, the bright spots that show up in those conditions, is annoying, but has no effect on sharpness. Diffused flare is a different type of flare, insidious because it's often missed, and it diminishes sharpness.

Flare occurs because light is bouncing around inside the lens. The better baffled a lens is in its interior, the less flare can bounce around. The popular zoom lens has a lot of glass elements inside, resulting in many surfaces for light to bounce off of, making this type of lens very susceptible to flare. Multicoating helps, but it doesn't eliminate flare.

If the light spreads out across an inside lens surface, diffused flare occurs, reducing contrast and sharpness and possibly affecting color. You often can see this effect by using your hand to shield the lens, blocking any direct light to it. A lens shade is a critical accessory for sharpness to prevent diffused flare problems. You also can use your hand or a hat to shield the lens from particularly bad flaring conditions.


Selective Focus
Our eyes respond strongly to contrast, but light/dark contrast is only part of the story. You can achieve a higher degree of sharpness by selective focus, a technique where the subject is sharp and much of the rest of the photograph is deliberately out of focus. This contrast makes the sharp areas look extra-sharp, and is best achieved with wide-open apertures (small ƒ-stop numbers) and telephoto lenses.

Sharpness Tips
While these seven elements of sharpness often aren't discussed, they're valuable techniques to use to increase the quality of your own images. Follow these guidelines for sharper photos.

1) Use a tripod and lens shade to ensure you capture the brilliance
and sharpness built into
a lens.

2) Look for ways to use contrast in and around your subject.

3) Use the direction of
the light effectively.

4) Watch out for image flare.

5) Contrast sharp subjects with out-of-focus surroundings.

6) Use a larger imaging format.

7) Be aware of grain or noise issues.

Selective focus can be a real benefit when you're handholding a camera. A small aperture may mean too slow a shutter speed to keep everything sharp (especially retaining image brilliance), resulting in much depth of field perhaps, but fuzzy sharpness. It's better to get something perfectly sharp using a wider lens opening and a faster shutter speed.

The concept of sharp/unsharp contrast also can be used to make a less-sharp image look better. Bring the image into the computer, then sharpen the part that needs to be sharp as best you can. Next, select the other parts of the photo and apply a Gaussian Blur until the sharp areas contrast with the blurred areas enough so that they look sharper.

Formats
Larger film formats and more megapixels offer more sharpness in larger images. This type of sharpness is strongly related to final image size. If you only printed small photos, you'd see little difference in image quality from 35mm to 4x5, or 4 megapixels to 17. But as your image size increases, such as going to a 16x20-inch print, the contrasty edges that define sharpness will become bigger. In the case of smaller-format cameras, that means those edges will start to lose detail, dropping sharpness.

Another effect not as commonly known is related to image brilliance. Medium-and large-format cameras, as well as larger-megapixel digital cameras, often will have superior image brilliance than 35mm or lower-megapixel cameras in moderate-sized prints. Sometimes, however, this is due to medium- and large-format cameras being used almost exclusively on a tripod compared to the more casual use of 35mm-sized cameras.

Gain or Noise
An anomaly of sorts regarding sharpness appears in grain or noise. Normally, we try to get rid of those image artifacts (something that appears in an image due to the technology used) or at least minimize them. But grain (and the digital equivalent, noise) can make a photo look both less and more sharp.

When grain becomes too strong, it obscures details, making sharpness an issue. On the other hand, if a viewer sees crisp grain in a print, he or she often assumes the photo is sharper than it really is.

One reason why many photographers wanted to use Kodak's black-and-white TriX film way past the time the company wanted to discontinue it was for its unique tonal qualities. On the downside, it's a grainy film, but photographers discovered that if you made sure the grain looked very sharp when printing the film in the darkroom, the image always appeared sharp.

The same goes for digital. A camera rep had pros complaining that the latest, high-megapixel camera was less sharp than the older models. He checked and discovered that the latest camera was so clean and noise-free that these photographers were missing it. He actually had to add grain to the photos to get them to believe it, too!

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