Highlights and Shadows
Your brake lights communicate important information to other drivers, like when you´re stopping! The information and details within the highlights and shadows of your image is also important. Don´t lose it please!
While our eyes are able to register a wider range of tones and luminosity than our camera, a correct photographic exposure should reproduce a scene with an appropriate contrast and full tonal range. If too much light reaches the sensor, the photo will be overexposed, and if too little, the photo will be underexposed. The dynamic range is the number of tones that a photographic sensor can capture in a given image. In digital cameras, the dynamic range is conveniently shown in the histogram.
Most digital cameras allow you to see the histogram once you have taken a photo. This graph can help you to evaluate the image’s exposure. All of the tones captured in a photo are represented in the graph. The horizontal axis shows the shadows on the left side, and the highlights on the right. The vertical axis shows the number of pixels at each level of lightness. The histogram is one good way to verify that the highlights aren’t “blown-out” or the shadows “blocked.”
Here is an example of blown-out highlights:
Example. The image below shows a lack of information or detail in the highlights. On the right you can see how the “blown-out” highlights or pure whites have no details, and therefore, no texture.
Below is an example of blocked shadows:
Example. In certain parts of the image, there is no detail in the shadows. On the right, you can see how the shadows on the grass fuse with the cow’s black hide.
Once the photo has been taken, all of the image edition programs allow you to evaluate the highlights and shadows of the image. As you retouch and adjust your image, you should verify that your changes aren’t causing important detail loss in either the highlights or shadows. This tonal compression and detail loss can occur if you give your image an excessive contrast. The “Info” window provides information about the density of the image in any given point by giving a reading of the values where the curser is. This window shows information both for RGB (light measurement) and CMYK (pigment measurement).
Make sure that your highlights aren’t blown-out by checking their numerical value on the info table. If they show 255 RGB or 0% CMYK, that area of the image contains no detail, only pure white. The whites should show at least 2% CMYK or 250 RGB.
A value of above 90% CMYK or RGB 5 is a pure black without details. However, the shadows/blacks shouldn’t go below CMYK 83% or they will lack contrast. Always try to use these tools, proper exposure, and careful editing to produce images with a well-balanced dynamic range.