What is Bit Depth?

Bit depth refers to the number of bits used to represent a unit of information in digital media. For images and video, this is color or brightness information per pixel, while for audio, it's the dynamic range and signal-to-noise ratio.

The concept of bit depth is simple - the more bits you have, the more precise your representation of data, but the more space you'll need to store it.

So, higher bit depths will allow for a greater range of colors or sound intensities, resulting in richer, more detailed, and more realistic media. For instance, an image (or video) with higher bit depth will display smoother gradients and fewer visual artifacts, while higher bit depth in audio delivers better dynamic range and clarity.

What is Bit Depth in videos and images?

For anything visual, bit depth directly represents the number of colors or shades per channel (red, green, blue, and, if present, the alpha/transparency channel) that can be displayed.

Let's look at this mathematically.

For an image with a bit depth of N bits per channel and three channels for RGB, the number of unique colors you could have per pixel would be 23N.

So, in an image or video that has 8-bit RGB, where each channel can have 28 = 256 possible intensity values ranging from 0 (no intensity) to 255 (maximum intensity), the total combinations are:

256 x 256 x 256 = 16,777,216

Meaning 8-bit RGB can represent about 16.7 million colors.

As you can see, the "bits" per channel determine how finely the color and brightness are divided. The more bits, the more colors you can have, allowing for more precise and subtle differences that are especially noticeable in gradients (or HDR content).

What are the common image and video bit depths?

• 8-bit: These support 256 shades per color channel, resulting in a total of approximately 16.7 million possible colors. Common formats like JPG, PNG, GIF, and any Standard Dynamic Range video (streaming, DVD, etc.) commonly use 8-bit depth, balancing file size and quality, making them efficient for everyday content where file size matters and high precision is not critical.
• 16-bit: Each channel can represent up to 65,536 shades, enabling over 281 trillion possible colors. This increased precision is ideal for tasks requiring smooth gradients, subtle color transitions, and advanced post-processing, such as photo editing in RAW, High Dynamic Range video, scientific imaging (MRIs, which often use 16-bit grayscale), and modern game engines and CGI that need realistic lighting and shadowing.
• 24-bit: Often referred to as true color, this is functionally the same as 8-bit, but the term "24-bit" is used specifically for 8-bit RGB (8 bits per channel), to make it stand out from 8-bit grayscale.
• 32-bit: Refers to 24-bit RGB with an additional 8-bit alpha channel for transparency. Suitable for advanced image editing requiring transparency layers.

Why Bit Depth matters for images and videos

The expanded color range for higher bit depths reduces banding artifacts (visible steps in gradients) and allows for smoother transitions between colors. It is essential for scientific imaging and any HDR content where brighter highlights and deeper shadows need precise representation without losing detail or clipping.

What is Bit Depth in audio?

In digital audio, the math is the same – bit depth here refers to the number of bits used to represent the amplitude (loudness) of each audio sample. The higher the bit depth, the more discrete levels are available to represent sound accurately, directly affecting the dynamic range—the difference between the softest and loudest sounds that can be accurately captured without distortion or noise.

What are the common audio bit depths?

• 16-bit audio: This is the standard for CDs, with 65,536 possible amplitude levels. It provides a dynamic range of about 96 decibels (dB), sufficient for most consumer applications. This level of detail ensures clean sound reproduction and minimal noise, making it ideal for casual listening and home audio systems.
• 24-bit audio: With over 16.7 million amplitude values, 24-bit audio offers a dynamic range of approximately 144 dB. This expanded range allows for greater precision, capturing subtle nuances in sound, such as faint background details and intricate dynamics in musical performances. It is commonly used in professional recording studios, audio mastering, and film production, where audio fidelity is critical.

Why Bit Depth matters for audio

Higher bit depths reduce quantization noise, which is the error introduced when approximating the actual analog sound wave with discrete digital values.

Consumer audio is fine with 16-bit audio as it already achieves noise levels below human hearing, but 24-bit is preferred for professional work to ensure cleaner recordings as higher bit depths retain more detail in audio during mixing and processing. This avoids artifacts when amplifying, compressing, or applying effects to the source.

What are the trade-offs of higher Bit Depth?

While higher bit depths improve quality, they come with tradeoffs:

Conclusion

Bit depth significantly impacts the quality of digital media, from images and videos to audio. It determines color precision, gradient smoothness, and sound clarity, making it a critical factor in both professional and everyday use.

Choosing the right bit depth depends on your specific needs: higher bit depths are ideal for professional workflows in photography, video production, and audio mastering, while lower bit depths can suffice for general use where file size and efficiency are priorities.

To optimize and deliver media efficiently without compromising quality, consider tools like ImageKit. Its ability to convert and optimize high-bit-depth content into web-friendly formats ensures a seamless balance between performance and quality for your digital projects.