Camera Basics #23 - Dynamic range of cameras (sensors)

Photon noise and ISO

The ISO makes the sensor more sensitive to light. As a result, it is easier to work in dark situations. However, the resulting noise hits the pixels of the sensor, causing the measured values to become noisy. This means that colors and light no longer contain all the information that they once contained at a lower ISO.

Depending on the model, the camera has a different basic sensitivity. If the photographer selects an ISO value below the basic value, the camera controls the sensor to overexpose and the highlights in the image are cut off. Of course, the camera actively works against this by darkening the midtones and shadows so that the overexposure is not particularly noticeable. However, this has the disadvantage that some of the highlights in the shot have already been lost and cannot be restored.

Cameras that work with a Dual ISO rely on two different capacitors that read the sensor with different ISO values. This increases the dynamic range, as black values, for example, are read out with a higher basic sensitivity. This offers a little more flexibility when brightening. At the same time, highlights can also be preserved because they are read out with the capacitor at the lower ISO.

So, what is photon noise? This describes the noise caused by the moving electrons. This cannot be physically prevented, but modern cameras and various algorithms are getting better and better at eliminating it.

What does the dynamic range depend on?

The most important factors on which the dynamic range depends are:

• Sensor design: Larger sensors (e.g. full-frame sensors) often have a better dynamic range than smaller sensors (e.g. APS-C, Micro Four Thirds).
  APS-C vs. full-frame explained
  However, the dynamic range of the sensor does not only depend on the sensor size, but also massively on the architecture or structure of the sensor. You can find more information on this in our Camera Basic article on sensors.

• ISO sensitivity: Lower ISO settings generally offer a better dynamic range, as noise increases at higher ISO values and details in the shadows can be lost.

• Pixel size / number of megapixels: Larger pixels on a sensor can capture and process more light, resulting in a better dynamic range. Cameras with fewer but larger pixels therefore often have a better dynamic range than those with many but smaller pixels.
  Megapixels explained

• Optical factors: It is not only the sensor that determines the dynamic range of the image, but also the glass. If a lens is prone to extreme flaring and ghosting, it is quite natural that less contrast is captured in the image. This can also be a look! But it's not just the glass of the lens that plays a role here, UV filters and other filters also play a key role. Depending on the quality of the glass, UV filters can absorb a significant amount of light. Light that passes through glass always has a certain loss. This is measured in the transmission, which is why an aperture of f1.4 does not reliably allow the corresponding light to enter. A real measured value here is T-Stop or Transmission Stop.

What kind of range do modern sensors usually have?

Dynamic range in photography refers to the difference between the brightest and darkest areas of an image that a camera sensor or film can capture - without losing detail in the shadows or highlights.

The dynamic range of modern system cameras varies depending on the model and sensor, but is typically in the range of around 12 to 17 f-stops. (as of 07.2024)

Making better use of the dynamic range

Modern system cameras offer various functions that allow you to make better use of the dynamic range than was the case with an SLR. For example, the system camera offers a function that allows you to display the highlights. This allows you to adjust the exposure to such an extent that the zebra stripes are reduced on the camera display. For landscape photography, you can also use gray graduated filters to reduce the contrast between the sky and the ground and to better exploit the dynamic range. If you are active in portrait photography, you can brighten up your model and differentiate them from the rest of the picture. You can also brighten up shadows on the face so that the maximum details are still visible, or become visible again.

What is the difference between dynamic range in photography and videography?

The dynamic range in photography and video differs in several aspects; mainly due to the differences in the technical requirements, the way the images are captured and processed.

In photography, the photographer is free to choose the exposure time and thus has the opportunity to store much more information in the image in a long exposure than is the case with many consecutive photographs. In addition, a RAW format is always available for photography. Not every camera can do this in video mode.

[If you record a video in RAW, you need a large amount of data. This is because 30-120 or more images are created per second. These can only remain within a certain exposure time according to the frames per second. This is why you often have to rely on an ND filter to achieve a high dynamic range. Another important factor for a high dynamic range of your video is the bit rate in which you record the video; videos in 8 bits, for example, tend to create a staircase effect, especially with a horizon.

The influence of compression methods

In the following, we will return to the compression of RAWs and the video codecs, although we will address video codecs and co. in further dedicated articles. Every camera manufacturer has its own way of compressing images, apart from JPEGs. Compression is usually non-linear, contrary to the sensor pixels, which is why there is a loss in the conversion of the scales.

In the case of videos, for example, a distinction is made between compression in h.264 & the more modern standard h.265, which have different effects on video quality. The h.265 standard is particularly interesting for video streaming, but the whole thing tends to distort the colors and black levels, especially in the black levels and shadow colors.

Mechanical shutter and electronic shutter

Some camera manufacturers limit the bit depth of RAW images depending on which shutter is used. This is important to mention because more and more camera manufacturers are abandoning the mechanical shutter. This means that the camera uses a different bit depth with the electronic shutter than when using a mechanical shutter. Anyone who shoots a lot in series and has set the switch between the different shutter types should therefore be aware of these bit depth differences. If you prefer to rely on consistency here, you should set your camera accordingly beforehand so that you have a consistent dynamic range.

Conclusion

Dynamic range is a very technical and difficult topic to communicate. We hope that we have been able to provide some clarity here. If you have a rough understanding of the principle, you can learn a lot as a photographer and save yourself a lot of frustration elsewhere.