1. Smoothing the intensities
Intensity
Smoothing
More
Smoothing

2. Intensity Derivative Smoothed Intensity First Derivative
Second Derivative

3. The Derivative of a Convolution

4. Analyzing a 2D image Image after smoothing and second derivative Image
Black = Negative
White = Positive
Zero-Crossings

5. Smoothing a 2D Image
To smooth an image, I(x,y), we can convolve with a 2D Gaussian:

6. Differentiation in 2D
To differentiate the smoothed 2D image, we will use the Laplacian operator:
We can again combine the smoothing and derivative operations:
(displayed with sign reversed)

7. Detecting intensity changes at multiple scales

8. Computing the contrast of intensity changes

9. The Eye

10. The Neuron Major parts of a neuron: Cell body Axon Terminal
Synaptic cleft
Dendrites

11. Projection from the Retina

12. Retinal Ganglion Cells
Retinal Ganglion cells have receptive fields that exhibit a
center-surround structure.