This blog has been merged with The Dusty Cellar. All new content will appear there. I apologize for the inconvenience.

Wednesday, March 30, 2011

Depth of Field 101

When you take a photo, 
depth of field or DOF refers to 
how much of your photo appears in focus.
You control DOF by controlling how large your lens opens.
But first, make sure you know these terms:
Aperture -
 An aperture is a hole or an opening in your lens.
So when you click, it means how large the hole in your lens will open. 
F stops -
How large the hole opens is usually measured in stops
called F stops and will often be written like this: f/22

You CAN control how large the aperture (hole) in your lens opens.

Above are two examples which are explained below.

Part 1:  A small aperture/opening/hole gives a deep DOF
as in the top daffodil photo.

If you see a beautiful mountain view
and you want to capture the foreground scenery in focus too,
you might choose the auto option
on your camera marked for scenery.
(Below is a Canon, other cameras are similar.)

This will automatically set your camera
to make a smaller opening (aperture) when it clicks.
It works just like when you squint your eyes -
more of the scene will appear in focus.

That is pretty basic right?
So let's try to understand it
if you were to shoot in Manual (M) or Aperture (Av/A) mode.
Since you want a deep DOF
to capture that scenery
(Lots in focus)
you will want to set your camera to "Squint"
and you do that by choosing a smaller f stop/opening.

Part 2: A large aperture/opening/hole gives a shallow DOF
as in the bottom daffodil photo above.

Let's say you want a photo
of your adorable son or daugher
but the background is busy and distracting.
In order to blur out that background 
you want a shallow DOF
so the focus is on your child
and not everything else.

You could choose the Portrait setting on your camera.

When you select the portrait setting 
the camera will automatically choose a larger opening/aperture/f stop
so that the background is softened/blurred.
If you were to switch to Manual or Aperture on your dial
you would choose a larger opening to reduce the amount of field
in focus.

Here is the easy....but confusing part.
Your F stop/aperture setting makes a SMALL opening when the F number is BIG
and a BIG opening when the F number is SMALL.
F 1.4 is a BIG opening
F 32 is a SMALL opening.

Once you can get your brain to remember that,
the rest is easy!

(PS Not all lenses can open up as much as others.
That depends on the lens you are using.
Larger openings are more expensive.)

If you are new to this
take you camera and set it up on a table or tripod.
Take 2 photos of a scene with objects placed
at varying distances from your camera
keeping the focus on the same point.
Take one photo with your portrait setting
and one with your scenery setting
and check out the difference
on your computer.

That is a quick and easy way to control some depth of field.

If your camera has the ability
and you 'get this'
you can take it a step further....

Set your camera up with a flower filling about half the frame,
focus on a point on the flower
but keep something else in the background.
(If you have a tripod this is a great time to use it.)

Set your camera on the Aperture setting (Av or A on the dial)
Choose the largest aperture/opening/f stop you can.
That means the smallest f stop/aperture number you can choose.
(Usually you will turn a dial to set the aperture,
and the f stop numbers will change as you turn the dial,
if not, you will need to check your camera's manual.)

Take a photo.
Move the setting one stop/one smaller opening/larger number.
Take a photo.
Move the setting one stop/one smaller opening/larger number.
Take a photo.
Move the setting one stop/one smaller opening/larger number.
Take a photo.
Keep doing this until there are no more stops.
Compare the photos on your computer.

Do you see how very little is in focus in the first photo?
As you move on, more of the flower is in focus
and eventually even the background is in focus.

You now have the ability to control 
the depth of field of your photos
for composition and creative purposes.

A large aperture is great for bokeh:
(Shallow DOF)

A small aperture is great for sun flares:
(Deep DOF)

Look for opportunities to choose 
a depth of field
to enhance your photos.

Improving composition
is the cheapest way to improve 
your photography.