American Registry of Radiologic Technologists (ARRT) Practice Exam

What is the relationship between pixel depth and the number of shades of gray in an image?

1. More bits = Fewer shades of gray

2. More bits = More shades of gray

3. More bits = No change in shades of gray

4. More bits = Limited shades of gray

The correct answer is: More bits = More shades of gray

The correct answer reflects a fundamental principle in digital imaging, where pixel depth, measured in bits, directly impacts the number of shades of gray that can be represented in an image. Pixel depth refers to the number of bits used to represent the color information for each pixel. When more bits are allocated to each pixel, it allows for a greater number of distinct values that can be assigned to that pixel. For grayscale images, this translates to a wider range of shades of gray. For instance, an 8-bit pixel can represent 2^8 (or 256) different shades of gray, while a 16-bit pixel can represent 2^16 (or 65,536) shades of gray. As a result, increasing the pixel depth provides a greater granularity in the representation of tones, allowing for smoother transitions and more detailed images. This relationship is crucial in various applications such as medical imaging, where high contrast and detail are essential for accurate diagnosis and analysis. Higher pixel depths enhance the ability to visualize subtle differences in tissue densities. Thus, more bits directly correlates with an increased number of shades of gray, allowing for improved image quality and detail.