Understanding dynamic range and how it relates to cameras and photography will enable you to make educated exposure related decisions.
The technical details concerning dynamic range are rather complex, so for simplicity’s sake, today’s discussion will be kept at a higher level and we won’t delve into the photons and pixels science.
It isn’t easy for electronic devices like digital cameras to realize the complete dynamic range experienced by humans. That said, the human eye has to adjust to the lighting of each scene and cannot process its full potential DR in one scene. For example, when you move from a well-lit room indoors to a moonless night outside, it takes a few moments for your eyes to adjust to the darkness. The same situation applies when moving from a dark room to a harshly lit, sunny scene. The variance between the dynamic range capabilities of a camera sensor and the human eye is what produces clipped blacks and blown highlights in high contrast scenes featuring both deep shadows and bright highlights.
In relation to ISO, generally speaking, the lower the ISO value, the larger potential dynamic range capability of your camera. As you move into higher ISO values, DR capabilities drop off as noise levels increase. This is important to know when photographing high contrast scenes such as landscapes. Utilizing a tripod can give you the ability to select a lower shutter speed and in turn a lower ISO than might be possible when shooting handheld. Digital camera technology has drastically improved over the last decade, and that includes advancements in dynamic range capabilities. We now have DSLRs that are equivalent to film in their DR latitude. Also, generally speaking, large sensor DSLRs will have DR capabilities that surpass their same generation point and shoot brethren.
While film is known for its highlight detail, digital images better retain detail in the shadows portion of the scene. Generally speaking, you want to properly expose for the subject of your scene. That said, if proper exposure of your subject is going to lead to blown highlights in important areas of your scene, whereas slight underexposure would retain that detail, you may choose to underexpose your subject in this situation. I recommend learning about and utilizing your histogram in order to achieve your desired exposure and to see where you might be losing detail in your highlights and shadows. Some cameras have the ability to turn on “highlight blinkies” that illuminate the blown highlight areas of your scene in red.
In the above image of the pine needles in water, I paid attention to my histogram and avoided blowing the highlights in the upper right reflecting portion of the image. Upon import to Lightroom, I saw that my shadows were slightly clipped (illuminated in blue.) Recovering that detail was very easily done by pushing the blacks slider to the right a touch.
High Dynamic Range (or HDR) photography is a method of combining multiple exposures of a scene in order to more accurately reflect the luminosity found in real scenes without the use of lighting equipment.
As photo technology continues to advance, we will likely see extended dynamic range capabilities in our future. Something else to consider is the capabilities and capacity of your monitor and print media, as each medium has it’s own DR limitations and capacity. If you are interested in reading up on the dynamic range exposure values of various DSLRs, the website dxomark has some great statistics and comparisons.