For those looking for a beginner level introduction to Fourier transforms and quantitative image processing, here is a talk I gave this year at the Advanced Imaging Methods Workshop: https://www.youtube.com/watch?v=Gsi8Cfy_3Po
It starts with an introduction to 2D Fourier Transform power spectrums and how to interpret them, then goes into filters and what each filter does to the information content of the image. I then go through real-world examples of how you can use just median filters, Gaussian blurs, and image calculator to denoise images and movies that appear at first glance to have an intractable background.
I then cover the basic math underlying deconvolutions, how perfect deconvolutions are theoretically possible, and then why real-world deconvolutions are inherently imperfect. And finish with using custom kernels to enhance image contrast (specifically showing the emboss kernel).
Unfortunately, this was a talk given virtually, and the platform was having a pretty significant video lag. That said, you can follow along with the talk yourself, go through the macro demo, and get all the example images covered in the talk here: http://bit.ly/3cYm4Z6