Photography - How to make the background blurred?

People want to make the background blurred so that their subject gets sharpness and focus.

The farther the background is from the object, the more blurred it will be. Some times you may need to move away from the the object so that background gets more blurred. So focus only the object then zoom to the fullest and also keep the object as far as from the background. If you zoom to the fullest, you may need to move backward to get the focus on the object.

In canon cameras, you can use Av (Aperture Priority) mode. As you increase aperture, focus on the object increases and background gets more blurred. Keep aperture as large as possible (i.e. small f-number). Then you can try the zoom for extra help. Note that, aperture gets smaller if you increase the zoom. Also, try to keep the background away from the object.

In summary, following are the important factors to consider:

• Large aperture (small f number)
• Full Zoom (Long focal length)
• Keep the background farther from the object
  

If you have SX10 then you can try 'Macro mode' [and keeping the camera closer to your object]. You can use 'Super Macro' if you can get close to the object. You may find the 'Super Macro' mode as difficult to use as it lacks the ability to zoom so you need to struggle to lock and focus. Best way is to use Macro mode and then zoom-in.


Otherwise, you can use photoshop after taking the image. Just select the background and blur the background. You may not get good results as it blurs the image uniformly irrespective of distance at which background objects are standing. Not sure if photoshop has option which applies blurriness depending on the depth of objects in the background.

Why does aperture decreases if you increase the zoom?
Aperture is described in terms of 'f-stop' or 'f-number'. It's the relationship between the focal length and diameter of the lens. If the focal length is 100 mms and the aperture's diameter is 25mm, then the f-number is written as "f:4".

When you increase the focal length (i.e., zoom-in) if focal length becames 200 mms, then the f-number becomes "f:4" even though aperture has not changed. The f-number always changes if you zoom-in or zoom-out.