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Photography Question 

BetterPhoto Member 		 

Filters for Pentax ZX-50


Ok you experts... I am pretty much of a novice even though I have been shooting for a few years. I have to take pics of a wedding in November. I have a Pentax ZX-50 with a 35-80 lens and a 80-200 lens. I have an extended lens which sits on top of the camera. I want to get some pics that sorta make the background look fuzzy, like a mist. Any suggestions would be greatly appreciated - like tips or filters, etc. Thanks


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September 27, 2000

 

John A. Lind 		 
 
  Hey, Knock Off That Racket!
Hey, Knock Off That Racket!
Example of eliminating distraction of a very cluttered backgroud reduction using DOF control.

John A. Lind

  
  Hanging Blossoms
Hanging Blossoms
Example how a simple, uncluttered background (lawn grass) greatly enhances using DOF control.

John A. Lind

  
 
One of the methods of doing something like what you describe is controlling the "Depth of Field." When you focus a lens, only the exact focus distance is in "critical focus," the sharpest possible focus you can achieve with the lens. Any distance other than this is something less than in "critical focus". Because the human eye and brain cannot detect that something is out of focus until it is sufficiently out of focus, it results in a "Depth of Field," or a range of distances that appear to be in focus, in front of and behind the exact focus distance.

If you can set the aperture of your lens, and work in "aperture priority" or completely manual mode, then set your lenses to their wider apertures, and this will leave your subject(s) in focus, with the background out of focus making it fuzzy looking. Many lenses have a DOF scale marked on them giving the approximate range of distances that will appear in focus for a specific aperture. The wider the aperture (lower f-number), the shallower the DOF. The smaller the aperture diameter (larger f-number), the larger the DOF. If the aperture is stopped down enough (f/16) the DOF will be very deep making almost everything appear to be in focus.

The caution is using too wide an aperture. If the DOF is too shallow and you have 3 rows of people, you may end up with the middle row in focus, and the front and back slightly out of focus. Depending on the focus distance and how deep a DOF you need, an aperture between f/2.8 and f/5.6 should work. The farther the background is behind your subject(s), the fuzzier it will get. How shallow or deep your DOF will be depends on lens aperture, lens focal length and the focus distance. If your lens isn't marked with a DOF scale, sometimes there are DOF tables provided with a lens when you buy it new (many people throw this stuff away along with the list of addresses for the warranty centers, etc.). If you don't have that, some of the major photo web sites have on-line calculators for computing it and you can make your own table for the focal length(s) you plan to use.

I've uploaded two examples. The first was taken of my dog with a very cluttered background. I used a shallow DOF to keep the dog in focus and greatly reduce background distraction. If everything had appeared in focus, she would have been lost in the clutter. The second shows how a less cluttered background (the grass of a lawn) enhances the effect even more!

-- John


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September 27, 2000

 
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