Creative Controls For Depth
of Field
By: Tedric Garrison
 If
we said that Depth of Field was the range of focus
found in any given picture, we would be partially
right. Just as a camera is the box that captures
light; it is also much more than that. A camera is
made up of many parts. Depth of Field also has many
parts. There are several other terms that relate to
what this particular concept of design can do for
us. The phrases Aperture, Shutter, ISO, Hyper Focal
Distance, and Bracketing are all good to be aware of
when you start to really “get into” Depth of Field.
Depth of Field (DOF for short), is usually
associated with the aperture which is often used
interchangeably with the word f-stop. The Aperture
controls the amount of light that passes through the
lens and onto the film; or in the digital world,
onto the sensor inside the camera. This amount of
light is determined by the size of the lens opening
(the aperture) inside the lens. On the older
traditional 35mm cameras, the settings on the
outside of lens that controlled this function were
called f-stops. That’s why even though technically
they are two different things; many writers use the
words aperture and f-stop as if they were one and
the same. It’s like calling the door knob, a door.
You do use one thing to affect the other, but they
are NOT one and the same.
The greater amount of light the aperture allows in,
the narrower the depth of field is, and visa versa;
the less amount of light the aperture allows inside,
the wider the depth of field is. Many beginning
students get confused by this. Since the f-stop is
what controls this light, the easiest way to
remember it is:
Small number = small f-stop (f 1.8) = small
amount of picture in focus.
Large number = large f-stop (f 32) = large amount
of picture in focus.
The Shutter also affects this same light; where as
the aperture controls “how much”, the shutter
controls “how long”. If the shot is exposed for too
long a time the photograph will appear washed out.
If the shot is exposed for too short a time the
photograph will appear too dark. This is commonly
referred to as: over exposure and under exposure.
Shutter Speed (how long things are exposed); can be
used to freeze things in midair (with a fast speed),
or it can be used to intentionally blur something
like water (with a slow speed).
 As
a general rule if you want to freeze something you
want a shutter speed of 1/500th of a second or
faster. As a general rule if you want to blur
something (on purpose), you would use a slow shutter
speed like 1/30th of a second or longer. Just
remember, that generally you only want part of the
picture as a blur so when you do use slower speeds,
also use a tripod.
Before your camera can set the correct aperture and
shutter speed for any given subject, it needs to
know how fast it can collect the light. The speed at
which this information is gathered is referred to as
the ISO speed. ISO stands for the International
Standards Organization; which is the group that
created the standard, so that if you got 100 speed
films in Germany, England, or Japan they would still
all respond the same way.
The general range of ISO speeds in all cameras
(digital or otherwise) is from 100 to 1600. The
higher the ISO speed the faster the camera collects
light, but it also adds more “noise” to the
photograph than lower speeds. This “noise” is what
older photographers often refer to as how “grainy” a
picture is. Most of the time you should use your
camera at a lower ISO speed if there is enough light
to do so. But for those times that you want to take
pictures in dim light without a tripod or flash you
can raise your ISO speed so your pictures are not
blurry.
Wherever you focus your lens within a given image,
there will be an area that is in focus and other
areas that are out of focus. The area that is “in
focus” is referred to as the “focal plane”. The
important thing to remember is that 1/3rd of this
focal plane is in front of whatever you focused on,
and 2/3rd’s of the focal plane is behind whatever
you focused on. By deliberately focusing 1/3rd of
the way into your landscape shot and using a high
number f-stop (like f-16 or f-22) you capture the
greatest amount of the photograph in sharp focus.
 Some
people have the mistaken idea that if you just set
your focus to infinity that it would do the same
thing. The infinity setting that looks like an 8
turned on it’s side, will give you an indication
that says anything say from 10 feet back will be in
focus. So what happens if you want to include
something that is less than 10 feet away? That’s
where the hyperfocal distance comes into play. When
you use the hyperfocal distance you focus on
something that is half of what the front infinity
setting indicates, in this case that would be five
feet. Since we know that 1/3rd of the area in front
of your picture will be in focus, it gives the
illusion that every part of your picture is in equal
focus. Whether you use the 1/3rd in rule or set the
hyperfocal distance, they both give you a greater
sense of a large depth of field which is good for
both landscapes and scenic shots.
If you always trust your camera meter and use what
it tells you, you are using what we what refer to as
a standard exposure value. Exposure Values are those
numbers that refer to the combinations of f-stops
and shutter speeds that can give you an accurate
exposure under a given light situation. Keep in mind
that your meter is a moron! Meters do not see in
color, in order to make up for this it will average
your scene, and give you a reading for 18% grey. All
meters do this it’s not their fault, that’s how they
were designed. But what happens if you actually want
a white wedding dress to look white? Or what happens
if you want that great black stallion to actually
look black? That’s where bracketing comes into play.
Most digital cameras and traditional 35mm cameras
will allow you to compensate or adjust the cameras
meter reading by 1 or 2 EV’s. Since most people do
bracketing by adjusting the f-stops this will also
effect your depth of field as well as your over all
exposure. If your moron, I mean your meter tells you
the perfect exposure is f-5.6 @ 1/250th of a second
that will give you an average reading for 18% grey.
If you want your subject to look brighter than just
average, you would shoot at say f2.8 @ 1/250th of a
second. If you want your subject to look darker than
average you would probably shoot at f-8 @1/250th of
a second.
 Just
as many pictures look better after you take them
into Photoshop and increase or decrease the
brightness or contrast settings; many images
actually look much better if they are exposed
slightly more or less than what the meter suggests.
This process of shooting above, directly at, and
below what the meter indicates is referred to as
bracketing. If you are in an especially difficult
lighting situation or a location that is in and of
itself very hard to get to . . . use bracketing. If
your camera batteries are getting low, use
bracketing. In short, if you have any doubts in your
mind at all, use bracketing. Not only will you be
guaranteed to get a useable shot, you might well get
a shot that is dramatically better than those who
trust a moron to make the decisions for them.
The more you know, the more you grow. Using these
controls to enhance Depth of Field in your pictures
will help take you to the next level. Not all
cameras will allow you to change all these features,
but if you explore your manual and find out what you
can control . . . you become the master. A great
photographer uses his or her camera as a creative
tool. Those who only take snap shots let the meter
(who is a moron) do all the work for them.
This Article Written By: Tedric A. Garrison Cedar
City, Utah
Tedric Garrison has done photography for over 30
years. In college; Tedric was an Art Major, and
firmly believes that “Creativity can be taught.”
Today; as a writer and photographer he shares his
wealth of knowledge with the world, at:
http://www.betterphototips.com.
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