Define bit depth and its effect on grayscale resolution.

• A. Bit depth is the number of bits used per pixel to represent gray levels; higher bit depth yields more grayscale steps and smoother images.
• B. Bit depth is the total number of pixels in the image.
• C. Bit depth determines the color of the image.
• D. Bit depth is the same as image resolution in line pairs per millimeter.

Answer: (A)

Bit depth refers to how many bits are used to store the brightness value of each pixel. Because each bit can be 0 or 1, the number of possible gray levels is 2 raised to the power of the bit depth. So with 8 bits per pixel in grayscale you have 256 possible gray values, which lets you create smoother tonal transitions. Raising the bit depth to 16 bits per pixel dramatically increases the number of levels (to 65,536), giving even finer subtlety in shades of gray. This directly affects grayscale resolution by expanding the tonal ladder, not by changing how many pixels you have or how sharp the image appears spatially. It’s about how finely you can represent brightness levels. It’s not about the total pixel count, nor about image color in the sense of hue, and it doesn’t describe spatial resolution like line pairs per millimeter.