Tuesday, August 21, 2012

What is the F number?

Most newcomers to photography are confused by the F number setting.  To put it quite simply follow this decision tree :

1.  Decide what parts of the image you want to have sharply focused. Here is a picture of a boy at nightime :


Since I wanted the model to be in sharp focus with the background nicely blurred I chose F1.8 as my aperture. Larger the aperture gives a smaller depth of field (DOF).

2.  Smaller the F number bigger is the aperture. This is because the aperture size is measured as a fraction with the denominator as the F number. Hence aperture of F/4 is smaller than  F/2.8.

3.  Checkout the picture below :


I wanted all the pillars to be in sharp focus so I increased the F number to F/6.3. Both foreground and background is sharp.

4.  Larger the F number gives a bigger depth of field.

PHOTOMANTRA : Small F numbers for portraits.

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