BlogImage Sharpness and Digital Photography - Skytravelnetwork

Preface: While the physics of photo-ography (the study of light) hasn’t changed since images were first recorded using silver emulsion (film), digital cameras present new challenges and opportunities to capture the images seen by your mind’s eye. The “intelligence” built into most modern digital cameras is nothing short of amazing. However, the trick is understanding and controlling how your camera “thinks.” All but the most basic of today’s digital cameras allow users to select from a number of predetermined settings, depending on the situation (portrait, landscape, shade, etc.). However, in essence those automatic settings take average photos under average conditions… and do a darn good job of it.

When we LOOK at a scene, we don’t SEE the entire scene. Without thinking, we’re selective. Our eyes are drawn to and focus on what attracts our interest. It could be an unusual cloud formation, a colorful bird in a distant tree, or a delicate flower at our feet. Naturally, to share our experience of the scene, we want our photo to draw the viewer’s attention to the part important to us. Problem is, no matter how intelligent your camera, it can’t read your mind (your mind’s eye). It can only guess what it is you want to capture and express with your photo. This is why you need to be smarter than your camera, and learn how to make it think and see like you.

A viewer’s eye is naturally drawn to the highest point of focus and image sharpness. So, controlling those properties of your photo is important to sharing with the viewer what you saw in your mind’s eye when you tripped the camera’s shutter.

Perceived image sharpness: It begins by accurately controlling what is in and out of focus. However, there are several other factors that will improve or degrade image sharpness. A few are unique to digital photography, but most others are the same as in the age of film cameras… just accomplished in a different way.

Motion Blur: Image blurring caused by camera or subject movement makes even perfectly focused photos appear un-sharp. Camera movement: using a tripod to reduce camera movement will help you get sharper photos. In addition, most modern camera/lens systems include image stabilization technology, designed to reduce motion blur caused by camera movement… especially handy when the shooting situation doesn’t lend itself to using a tripod. Depending on your camera/lens brand, this technology might be called IS (image stabilization), OS (optical stabilization) or VR (vibration reduction). It works by moving elements in the lens (lens stabilization) or by moving the image sensor (camera stabilization) to compensate for small camera movements.

However, neither tripod nor image stabilization addresses motion blur caused by subject movement. For that, we have to look for other solutions.

Shutter speed: Most people understand how a fast shutter speed can give us sharp photos of fast motion… a leaping football player or bird in midflight. Likewise, photos of moving subjects shot at slower shutter speeds will appear blurry or out of focus. Assuming image blur isn’t your creative choice, you will capture more sharp images using higher shutter speeds. This goes for animate people, animals/birds, or flowers and trees moving in the breeze.

It’s not all about the pixels: Although digital cameras with a higher pixel count potentially offer more detailed images, there are other factors that contribute to or take away from perceived image sharpness. Some of my most popular wildlife photos were shot with an older 12 megapixel Nikon and look as sharp or sharper as some shot with my new, higher-resolution cameras. Why?… because all the other factors were right on.

Optics, lens choice: Like any system, a camera/lens system is only as good as its weakest component. Sad but true, putting a cheap low-quality lens on a top-of-the-line camera will seldom give you the image sharpness achieved by a high-quality lens on a less-expensive camera. Professional photographers know this, and will often invest more than the cost of their camera on a good lens. Even then, you need to know the “sweet spot” or f-stop range of your lens that yields the sharpest focus. Usually, it’s in the middle range, but closer toward smaller apertures.

Subject lighting and contrast: Shooting digital, you have to keep in mind that digital imaging has a fairly narrow range of light sensitivity, and doesn’t accurately record anything that’s either too bright or too dark. The range of light we have to work with is less than that of film photography, and way, way less than what we see with our eyes. In order to resolve image detail, the level of light must be within the camera system’s sensitivity range. Everything outside this light/dark range is “clipped” (ignored). So, ultimately image detail depends on the amount and range of light reaching the camera sensor.                 

Working with exposure and contrast: Knowing the problems that too much contrast, and too much or too little light causes, what can be done about it? First, you need to accurately expose your photos. Under or overexposure results in the loss of sensor data and image detail. However, because of the way light sensors work, it’s generally better to slightly underexpose than to slightly overexpose. To deal with subjects having too much contrast, you need to someway reduce the contrast… this can be done by using fill-flash, reflectors, etc. to add light to the subject’s dark areas. Alternately, for static subjects, you might consider employing a technique called high dynamic range (HDR), where several shots with different exposures are taken to cover the full range of light on the subject… from darkest to lightest. Later, these shots are blended into a single image by photo editing software or the camera’s built-in HDR processing feature.

Impact of “noise” and ISO: Image noise is an inescapable reality of digital photography. Minimizing noise yields clearer, more detailed images, whereas more noise makes photos appear soft and less detailed. Without going into how image sensors work, what’s important is you understand how various ISO settings on your camera affect its sensitivity to light and the amount of image noise. Higher ISO settings will allow you to shoot subjects with less light, but at the cost of increasing image noise. It’s another balancing act. For any given subject or situation, the scales might tip one way or the other. Ultimately, it’s up to you to establish how much image noise is optimal or acceptable.

Testing and setting maximum ISO (for shooting auto ISO): If you shoot with your camera’s ISO setting on “Auto,” as I most often do, you need to set the maximum ISO you want the camera to use. While objective, scientific testing methodologies exist, a simple subjective test will tell you what you need to decide the best setting for your camera’s high ISO limit. To judge the amount of image noise your camera produces at higher ISO levels, I suggest setting up a low-contrast still life shot containing some fine detail. Then, set the camera on a tripod with all settings, except ISO, set to auto and the high ISO noise reduction set to normal. Next, starting from about ISO 400, take several shots while increasing the ISO setting for each shot. Finally, import the resulting photos into your usual photo editor and apply the same amount of noise reduction to each. Ask yourself, how much image noise and loss of detail you’re willing to accept, at what point would you simply rather forego the shot. That is the level at which you should set your camera’s maximum ISO. For my Nikon D800, I’ve established that limit as ISO 3200.

Role of file/data compression: I’m sure everyone realizes digital photography doesn’t record images at all, but rather converts what the lens sees into data about images. With few exceptions, digital cameras offer options for how the camera should record and store image data. Logically, the more data we capture and store, the more we have to resolve image detail/sharpness. In turn, the amount data recorded affects data file size, and the processing time required to record and store the data. Enter compression algorithms which are designed to preserve “essential data” while discarding “non-essential data.” There are others, but the most common compression scheme (file format) in use is jpeg (jpg). True, file compression results in smaller data files, allowing you to save more image files to your storage media. However, this comes at the expense of potential image detail… especially important when enlarging images.              

Conclusion and recommendations: The pursuit of image sharpness and detail is a multi-facetted balancing act. Addressing a single factor and ignoring the others won’t yield sharp images. The key is understanding the medium and mastering your camera/lens system. Craftsmanship isn’t about having the best tools, but rather knowing how to best use the tools at hand.

For sharp/detailed images:

  1. Use a high-quality camera and lens system
  2. Use a camera support (tripod, sandbag, etc.) whenever possible
  3. Focus accurately, with appropriate depth of field
  4. Expose accurately, considering range of light to dark
  5. Use the highest shutter speed possible for given situation
  6. Use the lowest ISO setting possible for given situation
  7. Use a file format that records the most image data

Post-processing techniques for sharpening images is another topic for another time. However, nothing takes the place of capturing sharp/detailed images in the first place.

To submit photography questions or comments, email [email protected]

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Sky Travel Network, Co.

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Phone: 224-707-0759

Email: [email protected]

BUSINESS HOURS

Monday – Friday : 9AM to 5PM

Saturday by appointment only

Closed on Sundays

CONTACT INFO

Address: 36 E Grand Ave.

Fox Lake, IL 60020

Phone: 224-707-0759

Phone: 224-707-0759

Email: [email protected]

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Image Sharpness and Digital Photography

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