Lenses & Depth of Field

Unblurred background



Blurred Background



 

Sometimes when you take a photograph the background appears blurry, but other times its crystal clear. Sometimes you want a completely unblurry photograph, but it comes out blurry and sometimes it’s the other way around. Do you wonder why this happens? Well this is called depth of field, which basically means the amount of blur your photograph has. Depth of field is affected by three important things, the space between you and your subject, the length of your camera lens, and the aperture. To describe this simply, if you are very close to your subject (like the flower shown above) then you tend to get more blur. If you stand farther away, then you will have less blur. The length of your lens is extremely important. You see, the photograph of the flower was taken with a 30-700mm lens and the one of the girl was taken with a 15-55mm lens. This means that the 700mm lens is a larger lens than the 55mm lens, so there is more blur. Your blur is also affected by your aperture.  The larger the aperture number is, then the less blur there is. This means that if your aperture is f/8.0 then there will be less blur than if you have it set to f/2.8. When you control these three elements, then you can control your depth of field. Of course it can be a lot more complicated than this, but this is as far into the subject as I dare go. Your depth of field also helps you gain the “bokeh” effect that everyone loves. Bokehs are the square-like lights that show up in your picture when it’s blurry. When you make your background very blurry, then you can achieve bokeh.  

 Bokeh