Question & Answer #1

April 28, 2012

Welcome to my first Question & Answer #1.  I'm going to start to Blog more often or answer questions you may have about photography.  Feel free to drop me an email from the Contact link.  I'll try my best to answer your questions.


Q: When I try to take photos especially Portraits with the back ground blurred, I am not very successful.  I use a zoom lens of 55- 250. Normally I try to use the largest aperture possible to reduce the depth of field.  But still the background does not come sufficiently blurred.  I know this can be done during post processing.  But I prefer to get it done while taking the photo itself if possible.

A: Most people first think of aperture as "getting the background blur (bokeh)" or depth of field (DOF).  I, myself first think of aperture as how much light I'm going to let in the camera.  Then I think about what kind of DOF I want.  Remember, aperture is the diaphram within the lens that can change in size/diameter.  The larger the opening of the diaphram ie. f/1.2, f/2.8 more light will be coming into the camera.


So, to achieve a good bokeh there's 3 things that you can control.

  1. Reduce your DOF by opening up the lens aperture to it's widest.  Since you have a Canon 55-250mm f/4.5-5.6, the aperture widest at 55mm is f/4.5 and at 250mm is f/5.6.
  2. Rack out (zoom) the lens to it's maximum.  In this case rack out the lens to 250mm.
  3. Get as close to the subject as you can.  Move in close to the point where auto focus will still lock on the subject.


With these 3 combination, you will get a very shallow DOF.  Usually when I want to increase my DOF, I will either back up a bit or zoom out a bit.


There is one more option, but it's something you may or may not have control over.  It's the distance of the subject from the background.