Ultimate Image Quality, Part II

Ultimate image quality picture taking techniques

Let's look at the techniques you should use to continue on the path of ultimate image quality while taking pictures. We're going to use those techniques to keep that image delivered by the lens to the sensor as sharp as possible while maximizing dynamic range of the image (which is just another way of saying getting a good exposure).

Before we get into the techniques, just a reminder that you should frequently clean your lenses, and occasionally the sensor. Each shooting session, check the front and rear elements of your lens to see if they need cleaning. And if small spots show up on your pictures, clean your sensor.


That old fashioned sharpness technique--a tripod.

Used properly, a sturdy mid-weight tripod (left) makes the ideal quality accessory for general photography.

The magnified portions, below, show the subtle blur that can degrade an image when you don't use a tripod. Top shot: with a tripod; bottom shot: without a tripod.Photos © Derek Doefflinger

Perhaps the greatest destroyer of image quality is blur caused by camera movement. There is always camera movement-unless you have attached your camera to a tripod. Even then, slight, image-degrading blur can result from camera vibration caused by mirror slap--the reflex mirror in your camera slamming into the pentaprism housing (okay it doesn't really slam as it is engineered to land softly, but it still vibrates the camera some).

Image-stabilized lenses, fast shutter speeds, and extra steady hands are all effective in reducing unsharpness caused by motion-induced blur. But only one technique offers the potential to achieve ultimate-image quality sharpness.

That's the use of a tripod.

Using a tripod regularly requires great discipline. So find one you like (at least medium weight) and start using it. Once the camera is on the tripod, do not take pictures by pressing the shutter button with your finger. Even though the camera may seem firmly supported it is still balanced on the apex of a triangle. That finger jab at the shutter button jars it, risking image blur.

Release the shutter by using a remote, a cable release, or the self timer. And consider going to the ultimate image release technique (especially when using long telephoto lenses), by setting the shutter delay function on your camera (not all cameras offer this feature). The shutter delay function makes the camera wait a few seconds for the vibrations caused by the mirror's movement to die down before it releases the shutter.

If you rely on image-stabilized lenses, use them with the same sharpness rule of thumb that you use with regular lenses: shutter speed = 1/lens focal length. You'll not achieve the same sharpness as using a tripod, but you'll come close.

Unspoken thus far and deserving more than this mention (but lacking the space), make sure that your lens is accurately focused on the subject. Not all autofocus mechanisms are precise. If you're shooting at f/8 or f/11, slight misfocusing may not be noticed but when you're using a large aperture such as f/2.8 with a telephoto lens for selective focus, focusing errors become noticeable.

Achieving the best exposure possible

A well-exposed photo, such as this image of Bryce Canyon, reveals details in the highlights and shadows, and allows you more leeway when making creative tonal adjustments.

One of the strengths of the RAW file format--its ability to compensate for exposure errors--is also one of its weaknesses. This inherently forgiving nature tends to encourage exposure sloppiness during picture-taking. So what if the exposure is slightly off? You can always fix it when adjusting the RAW file. And that may be largely true.

But relying on the exposure latitude of the RAW file is an undisciplined approach to taking pictures. And if you're like me, you often shoot JPEG files, and they require precise exposure. So let's look at achieving precise exposure so you can maximize quality at the time you take the picture and minimize software adjustments, regardless of the file format you are using.

What does a good exposure achieve? Technically, it gives you the maximum dynamic range possible with your equipment. Creatively, you may play with exposure for effects, but for superior technical quality you want to create an image file that reveals subject detail in both the shadows and highlights. Then you can play with dynamic range in Photoshop if you want.

In theory, achieving accurate exposure would require expert skill in using a handheld exposure meter. That may still be the best way, but using a built-in meter to precisely determine exposure requires both knowledge and experience, and maybe even a lot more time (and another article). There's a faster way. It's called the histogram.

Using a Histogram

I strongly recommend learning how to meter a scene with your camera's built-in meter so you can create accurate exposures of tricky scenes, but even then you'll use the histogram to verify your efforts. So let's get a short lesson on achieving an accurate exposure using the histogram.

To keep things simple, set your camera's meter mode to average or matrix. Take a picture of the scene and then display the histogram to review the exposure.

For digital exposures, you normally get best results by creating an exposure that comes to the brink of overexposure. That way you maximize image data and bring out a bit more detail in the shadows than you normally would.

The short lesson on the histogram is to slightly overexpose the image without creating clipping (jargon for overexposing the highlights in this instance). Most cameras have a display function that causes highlights of a picture displayed on the LCD to blink or flash if they are overexposed. You might want to turn on this function. Overexposure is represented by a vertical spike on the far right side of the histogram.

The histogram at right indicates this is a high contrast image with slight overexposure and more underexposure. I'm more concerned about holding details in the white skulls. Even though I think Camera Raw software can hold the skull detail, I took another shot at 1/3 stop less exposure.

Taming High Contrast

For any scene with meaningful white areas (picket fence, lighthouse, fluffy clouds, snow drift), you want them to appear on the histogram close to the far right side but not as a spike jammed along the extreme right. If the whites are jammed to the far right on the histogram or flashing on the image display, you need to reduce exposure a bit--usually one third to one half stop is enough--but let the histogram be your guide.

For images with high contrast, try a multiple exposure technique and later combine the images in software. An example of a high-contrast scene would be a white barn with its doors open and a dark green tractor inside that you want to show. For such a scene, you would take several pictures at different exposures: one that captures detail of the exterior of the white barn, another one or two exposures that let in more light to show detail of the tractor and barn interior. You'd then combine them in software using a high dynamic range (HDR) or other combination technique. Unlike a single exposure that would be unable to reveal detail in both the interior and exterior of the barn, the combined exposures can.

Compositional bracketing to maximize resolution.


To minimize excessive cropping and resolution dilution after taking the picture, try compositional bracketing.

When you find a scene worthy of ultimate image techniques, there's a good chance you may one day want to enlarge it to poster size. That means you need to keep its resolution close to the maximum possible. You can do that only if you crop it minimally or not at all when adjusting the image.

Choosing not to crop can be difficult, especially a few days after taking a picture. That's when you see it afresh and wonder why you didn't compose it tighter or vertically instead of horizontally--the result can be excessive cropping. So why not compositionally bracket those compelling scenes when you take the picture? Crop it tightly, crop it loosely, horizontally, vertically, from a higher or lower angle, or a completely different position. Work the scene! With many pictures to choose from, you can probably avoid cropping it excessively and maximize resolution so you can make outsize enlargements.And finally--the lens hood

Use a lens hood to block stray, non-imaging forming light from striking the lens and reducing image contrast.

Harsh lens flare, which typically appears when pointing the camera roughly towards the sun, can destroy pictures. It's often obvious in the viewfinder, appearing as bright streaks. But subtle flare may plague you with its almost unnoticeable haze veiling pictures. Slight image-wide flare can reduce the contrast of the entire image. To improve contrast and reduce flare, use a lens hood to block stray light from striking the exterior of the lens.

With the camera and lens properly set, the camera mounted on a tripod and a precise accurate exposure produced, you have now produced a digital picture file with ultimate image quality. You're ready for the final stage--adjusting it in software and then printing it with the settings and techniques that preserve the ultimate image quality you've achieved in the file.

Soon, a gorgeous, gallery quality print will be hanging on your wall.


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