模拟的图像输入到数字的图像输出需要经过Sampling和Quantization两步。
除了discrete level的数量之外，quantization的精度受噪音的影响非常大。
对于常见的2d sensor，
The quality of a digital image is determined to a large degree by the number of samples and discrete intensity levels used in sampling and quantization. However, as we will show later in this section, image content also plays a role in the choice of these parameters .
一般印刷的分辨率和灰度等级要求
As a very rough guideline, and assuming integer powers of 2 for convenience, images of size 256 256 *
pixels with 64 intensity levels, and printed on a size format on the order of 5 5 * cm, are about the lowest
spatial and intensity resolution images that can be expected to be reasonably free of objectionable sampling distortions and false contouring.
对于人眼来说，细节多少对于分辨率和灰度等级要求不同。
This result suggests that for images with a large amount of detail
only a few intensity levels may be needed.The most likely reason for this result is that a decrease in k
tends to increase the apparent contrast, a visual effect often perceived as improved
image quality