Depth of Field – In beginner speak “The Blury Background”

This is the first in a series of posts where I am going to try to explain some of the basic concepts of photography in “beginner speak”. If you like the concept, have anything to add, any futher questions or want to suggest another topic then let me know. Either add a comment below or email me.

If you have delved into the world of photography you will no doubt have come across the term “Depth of Field” or DoF. If not you’ll have seen some really great shots with the subject in pin sharp focus with a smooth blured back ground behind it. The ability to control and manipulate this affect is one of the most important aspects of photography. Depth of Field is the portion of an image that is in sharp focus. Controling the amount of a photo that is in focus is important for almost every shot from sweeping landscapes, where the whole scene needs to be sharp, to a headshot where only the subjects features need be in focus and anything else would be distracting.

Large DoF

Small DoF

 
The ammount of the image in focus can be easily controlled by altering four simple things.

• The size of the lens aperture
• The focal length of the lens (how zoomed in you are)
• The distance of the subject away from the camera.
• The distance of the background from the subject.

Easy hey! So if you want a really shallow depth of field, the blury background, open up the aperture as far as you can (small f/numbers), zoom in and get close to the subject and get as much separation between yourself and the background as possible. See my results in my post about a depth of field assignment I tried.

If you want a large DoF, well, do the oposite. Close down your aperture to f/11 or f/16, stand back a bit from your subject and zoom out.

If you want to be able calulate what DoF you camera will produce at given focal lengths the you can use the useful calculator at DofMaster.

The next step is to get out there and try it. As with everything trail and error is the key and with digital it won’t cost you a penny. Why not post a link to your effots in the comments below. Bear in mind that if you have a P&S camera (any camera with a fixed lens) you will struggle with the small DoF affect. This is beacuse there are a few other variables that control DoF that I haven’t mentioned, mainly sensor size. The small sensor means a very large DoF so you will only be able to achive the blury background in extreme circumstances. Give it a go and see what you get.