# How many pixels support each neuron in multi-layer CNN?

I'm studying for a computer vision module and I'm on the deep learning topic, in one past paper we have the following question:

Given that a convolutional neural network has five convolution layers (all the convolution layers are composed of 3×3 convolution filters with stride 1 and no pooling layers), calculate how many pixel(s) in the input image are supporting a neuron in the fifth layer?

without the input size of the image, how is it possible to work this out?

• – D.W.
Jul 2, 2021 at 20:11

If there is only one convolution layer, then every neuron is supported by $$3 \times 3 = 9$$ pixels in the input image. This doesn't depend on the size of the image. You can generalize this to more layers.