When it comes to image filters, these day's it often a case of choosing between Instagram's Hudson or Hefe. But in reality those filters are combination of several, simpler effects -- and this video explains how they work.
If you used Photoshop before the era of Instagram, you'll have at least read the names of things like Gaussian Blur and Edge Detection. They're what are known as low-level filters, that can be combined in the right way to create the sorts of image manipulation you see as standard in Instagram. In this video, image analyst Dr Mike Pound explains how the basic filters work at the pixel level.
Image by PRO Stròlic Furlàn under Creative Commons licence