From the course: Photography Foundations: Lenses

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Depth of field (DOF)

Depth of field (DOF)

You should already be comfortable with the concept of depth of field and understand how aperture choice impacts the depth of field in an image. If you're not, then go watch the Foundations of Photography: Exposure course or at least the depth of field and aperture bits of it. To shoot shallower depth of field, you need to use a wider aperture. One that has a lower f-stop number. So f/2.8 yields an image with less depth of field than f/11. Now the thing is not all lenses can open their aperture all the way to f/2.8. For all sorts of complex physics and optical reasons, the lens has to be engineered specifically to manage an aperture of a particular size. This means that every lens has a maximum aperture size to which it can be opened and that size is written on the front of the lens. For example, here is a 50mm lens that has a maximum aperture of f/1.8. I know that because right here it says 1:1.8. Maximum aperture is often expressed as a ratio like this. Now check this out. This is…

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