The term “dynamic range” denotes the contrast ratio between the brightest highlights and the darkest shadows. It also refers to the capacity of a light-sensitive sensor or film to capture details across these extremes of luminosity.
Let’s imagine a scene where the range of extreme luminance values—from the deepest shadows to the brightest highlights—is 16 stops (or 16 EV, short of exposure value). For example, a spot meter reading in the shadows would indicate 1 s at f/4, and in the highlights, 1/32,000 s at f/4. The human eye is capable of perceiving details across such a range—it can even handle up to 20 stops.
Whether film or a digital sensor, even the most high-performance light-sensitive surfaces cannot capture in a single shot the full dynamic range that the human eye is capable of discerning. However, in most cases, the dynamic range of the subject rarely exceeds that of the film or sensor.
Average Dynamic Range
A scene with a dynamic range of 7 EV or stops is considered normal. A typical example is an outdoor portrait or a street scene, under a cloudy sky or in the shade when the sun is shining directly. Depending on the subject and lighting conditions, dynamic ranges vary.
The most common ranges are between 5 and 10 EV, but more extreme situations can occur. Simply measure the darkest part of a scene in spot metering mode, then the brightest part, and calculate the difference. For example, if the first reading is 1 s at f/8 and the second is 1/2000 s at f/8, the difference is 11 IL.
Extended Dynamic Range
Depending on the film and the development process—particularly with black-and-white films and the right developer—a dynamic range of 14 stops can be achieved. As for sensors, DXOMARK lists about 50 camera models that perform just as well, offering a good exposure latitude for most situations.
The vast majority of sensors designed over the past decade—from 4/3 to full frame—deliver a dynamic range of at least 12 stops. Of course, this requires shooting in RAW format to make the most of the sensors’ capabilities and prioritize low ISO settings. At very high ISO settings, you lose 1 to 2 stops.
Low dynamic range of the subject
If you can do more, you can do less. There are scenes—particularly in foggy conditions—where the subject’s dynamic range is reduced to less than 5 stops. The tones in the image occupy a small portion of the histogram.
Low dynamic range of reversal films
Conversely, the dynamic range of certain light-sensitive media is limited when it comes to image capture. This is the case with color reversal films (Kodak Kodachrome and Ektachrome, Fujichrome Provia and Velvia, etc.), whose dynamic range is much more limited than that of negative films and digital sensors: 5 IL.
Nevertheless, there are countless masterpieces created with these films by masters of color such as Ernst Haas, William Eggleston, Harry Gruyaert, and Alex Webb.
Photographers used to “make do”, adapting the film’s limited dynamic range to aesthetic choices, particularly by prioritizing detail in the highlights and letting the shadows play out as best they could. In digital photography, the principle remains the same in terms of exposure: we prioritize detail in the highlights, except that where a reversal film starts to lose detail between +2 and 2.5 stops of overexposure, a sensor can go up to +3 or even +3.5 stops. And its ability to recover detail in the shadows is incomparable to that of film.
Dynamic Range and Bit Depth
Dynamic range should not be confused with the image’s recording sample depth, which is expressed in bits. Most cameras today offer 12- or 14-bit recording, which can be confused with a dynamic range of 12 to 14 stops. Bit depth refers to the color and brightness information for each pixel in the image. The higher the number of bits, the greater the range of color and brightness nuances for each pixel. With 12 bits, we get 4,096 values; with 14 bits, 16,384.
Dynamic range and bracketting
From both a quantitative and qualitative perspective, the sensor’s dynamic range and bit depth are two different things, but they both determine image quality. A high bit depth provides better reproduction of color and brightness gradations.
On the other hand, if the sampling depth is high (for example, 14 bits), but the sensor has a standard dynamic range of 12 stops, this does not compensate for the loss of color and brightness information in highlights or shadows compared to a sensor with a wider dynamic range (for example, 14 stops) and lower sampling depth (12 bits). If the subject’s dynamic range exceeds that of the sensor, bracketing over two or three shots is necessary to merge them in post-production. This trick extends the dynamic range.
Discover the professional photography courses at Spéos
Spéos photography school offers professional photography programs in 1 year, in 2 years, short photography programs (in 2 months and in 5 months), as well as photography workshops.
The long courses to become professional photographers allow you not only to master all the photographic techniques and its vocabulary (blurs, hyperfocus, sharpness zone, depth of field, backlighting, focal length, shutter release, autofocus, wide-angle, rule of thirds, etc.), but also all the stages of shooting and image processing.
Visiting the school allows you to discover the premises, the studios and the equipment, and is undoubtedly the best way to familiarize yourself with your future way of working. This is why, in addition to the open days, Spéos offers throughout the year personalized visits by appointment to come and discover the school with a member of the team.
Text and photos: Philippe Bachelier, teacher of Printing techniques at Spéos