Why You Should Care About Your Camera's ADC

A modern digital camera

LongHa2006 / Getty Images

ADC stands for Analog to Digital Converter and refers to the digital camera's ability to capture reality and convert it into a digital file. The process takes all of the color, contrast, and tonal information of a scene and adapts it into the digital world by using the basic binary code of all computer technology.

All digital cameras are assigned an ADC number and it is given in the manufacturer's technical specifications for each model. It is important to understand what ADC really is, how it works, and why it may play a role in your next camera purchase.

What Is ADC?

All DSLR and point and shoot cameras have sensors which consist of pixels with photodiodes. These convert the energy of photons into an electrical charge. That charge is converted to a voltage, which is then amplified to a level at which it can be processed further by the digital camera's Analog to Digital Converter (called the ADC, AD Converter, and the A/D Converter for short).

The ADC is a chip inside your digital camera and its job is to classify the voltages of the pixels into levels of brightness and to assign each level to a binary number, consisting of zeros and ones. Most consumer digital cameras use at least an 8-bit ADC, which allows for up to 256 values for the brightness of a single pixel.

Determining the ADC of a Digital Camera

The minimum bit rate of the ADC is determined by the dynamic range (accuracy) of the sensor. A large dynamic range will need at least a 10-bit ADC to produce a large number of tones and to avoid any loss of information.

However, camera manufacturers usually over-specify the ADC (such as with 12 bits instead of 10 bits) so as to allow for any errors on it. Extra "bits" can also help to prevent banding (posterization) when applying tonal curves to data. However, they will not generate any additional tonal information, apart from noise.

What Does This Mean When Buying a New Camera?

We have already said that most consumer digital cameras have an 8-bit ADC and this is sufficient for amateurs who are snapping pictures of family or capturing the beautiful sunset. The ADC plays a larger role with higher-end DSLR cameras at the professional and prosumer levels.

Many DSLRs have the ability to capture with either higher ADC ranging like 10-bit, 12-bit, and 14-bit. These higher ADCs are designed to increase the possible tonal values that the camera can capture, creating deeper shadows and smoother gradients.

The difference between a 12-bit and 14-bit image is going to be very slight and may even be unnoticeable in the majority of photographs. Also, it is all going to depend on that dynamic range of your sensor. If the dynamic range does not increase with the ADC, then it cannot be effective in improving image quality.

As digital technology continues to improve, so will the effective image tonal range and the camera's ability to capture it.

It should also be noted that in most DSLR cameras, the ability to capture images using any ADC above 8-bits will require shooting in RAW format. JPGs only allow for an 8-bit channel of data.