In this lesson I talk about the concepts related to achieving a blurry background when shooting. For many, you might think this is simply a matter of setting your camera to the lowest f-stop setting available and focusing on your subject. We go much deeper than that to show why closing down the aperture in your lens makes a deeper distance sharp and why f/2.8 on one lens will not produce the same results on another. In the process you'll learn about concepts such as the circle of confusion, infinity focus, relative vs absolute apertures (although I don't use that term) and much more. I also share a formula for achieving shallow depth of field and show many examples of where the typical approach failed me and I needed to modify my approach to successfully achieve a blurry background.Throughout this lesson, I tried to stay away from technical aspects that are not helpful in practical application, but are useful in arguments where people want to prove their technical knowledge. That means I did not get into hyperfocal distance or spatial compression even though I know it has a large influence on how the background will be rendered.Note: There are no downloadable practice images for this lesson. Also, there was a mathematical error in this lesson where the aperture size for the Nokton 25mm lens was listed as 23.75mm when it should have been 26.3mm. That error doesn't change the point that was being made, so if you didn't notice it, there's no need to review the lesson.