What is Bit Depth?

Bit Depth refers to the number of colours and shades available in an image.  For colour images, the number of bits is used to determine how many colours can be available within an image. For grayscale images, it determines the number of shades available within an image. 

Digital images can be produced in colour, grayscale or bitonal (black and white). For photography, we normally use colour or grayscale (e.g. for monochrome).  

The “bits” in an image, refers to the binary 0’s and 1’s which specify the colour/shade stored within each pixel of the image. Each bit can contain two values, so a 1-bit image will use two colours (bitonal images are 1 bit). Whereas an 8-bit colour channel can contain up to 256 colours.

File formats such as JPEG and RAW use multiple colour channels to store the brightness information for each pixel. Which drastically increases the number of colours and shades available per image. E.g. JPEG files use three different 8-bit channel’s in red, green and blue (known as RGB) to store the brightness information for each channel. Each of these channels is capable of storing up to 256 colours, giving us up to 16,777,217 colour shades per image.

The table below compares the number of colour shades available in popular bit depths used in photography.

Number of bits (Bit depth) Number of shades per channel RGB Colour availability
8 256 16.78 million
12 4096 68.68 billion
14 16384 4.39 trillion
16 65536 281 trillion
The Sky Garden in London, UK by Alison Fay

What Bit Depth does my camera use?

Your camera’s bit depth can vary depending on the camera type, model and the format your photos are saved in. Different file formats have different limitations on what bit depth they can be stored in, for example TIFF and JPEG images can only be saved in 8-bits or 16-bits.

The majority of DSLR and mirrorless cameras will capture RAW in 12 or 14bit. Whereas for JPEG and TIFF they normally capture the image using a 16-bit channel for rendering, and output at 8-bit.

Smartphones such as the iPhone X, capture images in 8 or 10-bit depending on the image’s file format and your camera phone’s settings.

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What bit depth does my image editing software support?

Any decent image editing software such as Gimp, or Adobe Lightroom, will be capable of supporting 8-bit and 16-bit without problems.

Adobe Photoshop has been able to support 16-bit since the 1990s, with the latest CC versions able to support up to 32-bits which are used for high dynamic range (HDR) images. Although most images you will edit in Photoshop will be 16-bit (E.g. RAW files) or 8-bit (e.g. JPEG files). Adobe Lightroom is able to support 8-bit and 16-bit images, and when exporting an image you can change the image’s bit depth to 8-bits or 16-bits.

Gimp can support 16-bit and 32-bit colour channels (as of version 2.1, which was released in April 2018). Snapsneed (Google’s app for editing your mobile images), supports 8-bit and 16-bit files.

If you want to learn more about photography, check out my other photography guides.

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