Calculating the Number of Parameters of a 2D CNN Layer
When we say the filter size if 5x5 it is for an image with 1 input channel, for three the filter size is 5x5x3 (but at a lot of places this additional info is skipped to make things easy to understand). When you apply a kernel of 5x5x3 to an image the output is just one channel. To get an output of 8 channels you need 8 such kernels. In that case, the number of parameters would be 5x5x3x8.