Some thoughts on image clarity and perceived image sharpness in relation to; Subject Sharpness, Color Value, Image Contrast, and Localized Image Contrast.
Subject Sharpnessis the result of several factors including the camera focus, depth of field, camera support, and proper shutter speed relative to subject motion.
Subject Sharpness cannot be altered by any post processing tool or fix. The image sharpening tools found in Camera RAW or Lightroom should not be considered an acceptable manner of “fixing” subject sharpness. Subject Sharpness is a result of the decisions made at the time of capture. Get it right in the camera!
Color Valueis the amount of detail or separation of color values within an image. It is primarily dependent upon the bit-depth of the image capture. A j-peg format image is 8 bit color, this means that each color has 256 distinct color values. An image captured by a Canon 40d in RAW image format is 14 bit color and has 16,384 distinct color values.
If properly processed a 16 bit image will always be perceived to be sharper than its 8 bit counterpart. My good friend and excellent digital photographer, Jeff Morgan, disagrees with me on this point, but if you (or he) were to visit my studio I can show you results of image tests that prove this. Capture your images in Camera RAW format and learn to use a conversion software, your images will have greater clarity.
Image Contrast is the overall contrast or range of density values from highlight to shadow detail. Images of high contrast have dark blacks with little or no detail and bright highlights with little or no detail.
Image Contrast is best controlled in the “Basic” module of Camera RAW or Lightroom. The sliders that control overall image contrast are: Exposure, Recovery, Fill Light, Blacks, Brightness, and of course Contrast. Adjustments here are as individual as the photographer’s vision and subject. There is no absolute right or wrong with respect to proper image post processing. Generally speaking, however, large corrections usually leave some kind of tell-tale defect in the image, which if you print the image larger than 5×7, becomes immediately apparent. A philosophy of “Less is More” will serve you well when using these tools.Localized Image Contrast is the separation of color values in the image. Images with greater Localized Contrast have a more pronounced separation of color or density values within a given color or density range, Localized Contrast can be increased without changing the detail in the shadows or highlights.
Localized Image Contrast is also controlled within the “Basic” module by the Clarity, and to a lesser degree the Vibrance and Saturation sliders. The Clarity adjustment will increase or decrease the tonal separation of color within your image. The Vibrance adjustment will increase or decrease the intensity of neutral or mid-tone colors before increasing more vibrant colors like bright reds, yellows, or oranges. Therefore the Vibrance adjustment can be perceived to increase Localized Image Contrast . The Saturation adjustment can increase or decrease overall color saturation-it effects all colors equally regardless of their brightness or hue. Again-the “Less is More” philosophy will help you keep your clarity of vision.
If you capture your images in j-peg format you have surrendered all of the above (with the exception of Subject Sharpness) aspects of image clarity to the default settings of your camera’s image processor. By taking this route you have predetermined most of the thoughtful decisions that are available to you to in the post processing phase of image making.
Localized Image Contrast is also controlled in the “Detail” module by the sharpening tools, however, I will leave that discussion to next month’s newsletter.