Approximately how many bits does ~60 gray levels correspond to?

• A. About 8 bits
• B. About 5.9 bits
• C. About 4 bits
• D. About 12 bits

Answer: (B)

The key idea is that the number of bits represents how many distinct levels you can encode, and that many levels correspond to the logarithm base 2 of that count. In other words, bits = log2(number of gray levels). For 60 gray levels, log2(60) is about 5.9 because 2^5 = 32 and 2^6 = 64, and 60 lies between these two powers. Since it’s just under 64, you’re just under 6 bits, roughly 5.9. Note that 8 bits would give 256 levels, 4 bits would give 16 levels, and 12 bits would give 4096 levels, so 60 levels sits closest to about 5.9 bits.