The people in the black and white picture were moving.

那张黑白照片上的人物是活动的。

Except if you move your eyes and look at a different area of the image, you see that you're actually looking  at a black and white picture.

除非您移动眼睛并查看图像的不同区域，否则您会发现您实际上是在看一张黑白图片。