angle lenses produce greater depth of field than telephotos
only when used from the same distance at the same aperture.
However, apparent perspective differs, making the choice
of focal length--and shooting distance--important creative
considerations. (Tamron AF 20-40mm zoom; at f/16; B+W
Photos © 1999, Peter K. Burian, All Rights Reserved
Aside from the intricacies
of exposure and light metering, photo enthusiasts generally find depth
of field the most difficult concept to master. That's understandable
particularly since this is a hypothetical factor based on subjective
judgment. Granted, some do develop an intimate appreciation of the technical
aspects, while others memorize them for night school courses when required
to do so, but many ignore them almost entirely or absorb only the bare
necessities. I must admit that depth of field seemed like an abstract
theory at first, when lectures on "circles of confusion"
pretty well described my reaction to the entire issue.
Eventually, I did grow to appreciate its practical value for problem-solving
and for achieving specific effects for creative purposes. The scientifically
minded can find plenty of data on depth of field in previous issues
or in one of Harold Merklinger's excellent books frequently advertised
in "Shutterbug Shopper." However, if you do not fall into
that category, consider the following tips for controlling depth of
field. I'll present these in purely practical terms, in a step
by step manner, with new information added in each section. My apologies
for any over simplification to technically inclined photographers and
college instructors everywhere.
·Understand The Basics. In layman's terms,
Depth Of Field (DOF) can be defined as the "zone of acceptable
sharpness" that extends behind and ahead of the focused point.
In truth only the focused plane in any photo is truly sharp. However,
objects in front of that plane and behind it, may also appear adequately
sharp to the eye of the viewer. The extent of sharpness (or only slight
blurring) differs based on several criteria, as we'll see in further
sections. Textbooks discuss the "circles of least confusion"
when explaining DOF, but that is a technical matter not necessary for
Example: You set focus on the eyes of a Bengal tiger sitting in the
shade at a safari park. The eyes will be rendered as tack sharp on the
negative. However, its snout--and the bark of the tree behind the animal--will
also appear in acceptable focus in the final print. The degree of blurring
increases gradually as you move from the focused point: the eyes. Objects
in the near foreground and distant background become progressively less
sharp the farther they are from the cat's head.
higher shutter speeds are required to prevent image blur
in low light, you'll need to set a wide aperture unless
using a tripod. This makes stopping down for expanded depth
of field impractical. In that case, refer to the other techniques
described to achieve acceptable results. San Simeon State
Monument. (Contax G1 with 28mm lens; f/2.8 at 1/15 sec;
Fuji Super G 800.)
·Select The "Right"
Aperture. Aperture size is the primary factor that influences
depth of field. In a nutshell, apertures of small diameter (denoted by
large f/numbers) such as at f/16 or f/22 produce an extensive range of
sharp focus. Foreground and background elements can appear reasonably
sharp. Conversely, wide apertures (small f/numbers) such as at f/2.8 or
f/4 produce shallow DOF. Much less of the foreground and background appears
A decisive choice of aperture (f/stop) is an essential ingredient in "making
a photograph" instead of simply "taking a picture."
Even when using a Program mode, you should shift to the most appropriate
f/stop/shutter speed combination when feasible. Take care however, as
long exposures will create blur from subject movement or from camera shake
if shooting handheld. Hence, you may need to compromise: select a wider
aperture than would be ideal in order to maintain an adequately fast shutter
speed. (Or use one of the other techniques for increasing DOF without
stopping down to very small apertures.)
Example: You are taking a picture of a scene framed by a stone archway
in England. You set focus on the fountain in the near midground and trip
the shutter. In fact, you take six pictures, the first at f/4, the next
at f/5.6, and so on down to f/22. Afterward you examine all of the 8x10
In the first at f/4, neither the archway nor the background castle appears
sharp. By f/11, they seem "almost sharp," but not quite up
to your standards. By f/16 the arch, fountain, and background castle all
appear adequately sharp, and your friends consider this the best picture.
The image made at f/22 is blurred by camera shake due to the long shutter
speed because you did not use a tripod.
creative nature photography, "vignetting" the
primary subject can be an effective technique. Here, I achieved
exactly the intended effect with the following: a telephoto
lens, moving in extremely close to foreground subjects and
a wide f/2.8 aperture. (Canon EF 70-200 f/2.8L USM at f/2.8;
·Switch To A
Longer Or Shorter Focal Length. Anyone who has used a 28mm and
a 300mm focal length will have noticed that wide angle pictures usually
have extensive depth of field. Conversely, those made with telephotos
generally have a very narrow DOF. This typically leads to a simple conclusion,
which is also published in some magazine articles: "The longer the
focal length, the less depth of field at any given aperture setting. If
you want greater depth of field, use a shorter focal length."
Myth Breaking Example: The above definitely seems to be an accurate assessment
of DOF in practice. Actually, it is a half-truth, but a persuasive one.
It is an optical fact that DOF does not change with different focal lengths.
Don't believe it? Then try a controlled test with a 35mm and a 200mm
lens. First, take a picture of a friend standing next to a long, flowering
hedge with the telephoto. Then switch to the wide angle lens and move
in very close to the subject--in order to keep her as large in the viewfinder
as in the previous shot.
Examine the resulting slides with a 10x loupe and you'll notice
that the zone of acceptably sharp focus (check the blossoms) is nearly
identical. Granted, perspective differs: the rendition of lines and shapes
are definitely not similar nor is the apparent distance between objects
at various distances. Wide angle lenses produce "expanded perspective,"
increasing the apparent distance between objects. This can create an optical
illusion which makes the casual viewer believe that DOF differs in the
a 4x6 print, both buildings appear in focus thanks to extensive
DOF; by 8x12 the one farthest from the lens is less sharp,
but still highly acceptable. Move up to a 16x20 however,
and the lack of critical sharpness becomes quite apparent.
Epcot Center, WDW, Florida. (Canon EF 20-35 zoom at 20mm;
f/11; Fuji Super G 200.)
·Vary The Focal
Length From The Same Position. To be fair, telephotos do reduce
DOF, while wide angle lenses expand it--but only when you shoot from exactly
the same distance to the subject. It is actually image size which affects
DOF, regardless of the lens. Whether you fill the frame with a telephoto
from a distance or simply walk closer to the subject with a shorter lens,
DOF will be shallower.
Example: Sit down on the grass across the street from an historic mansion
and take a picture of the entrance area with a 28mm lens at f/5.6. Stay
in the same spot, but switch to a 100-300mm zoom, taking three more frames:
at 100mm, 200mm, and 300mm, all at f/5.6. Examine the prints and you will
note that the door appears larger and larger in each successive photo,
and the zone of acceptably sharp focus is noticeably less with each longer
So, a telephoto really does produce less DOF than a wide angle lens? Yes,
but only when used from the identical shooting distance. It is the increasing
subject size (at the greater magnification) which reduces the zone of
acceptably sharp focus.
·Change The Camera To Subject Distance. As I have
already implied, DOF is affected by the camera-to-subject distance. When
you focus on something which is very close to the lens, you'll get
very little depth of field. As you focus to greater distances--and this
varies on focal length--DOF becomes more extensive.
Hint: When shooting extreme close-ups as in macro nature photography,
remember that DOF will be measured in fractions of an inch. Position the
camera so the back (film plane) is parallel to the subject plane--perhaps
the wings of a Monarch butterfly. Now you need not stop down to a minuscule
aperture such as f/32 to keep it all within the depth of field. The higher
shutter speed available at a wider aperture will cause less risk of motion
blur from camera or subject movement. As a bonus, the optics will provide
higher resolution, as most lenses do at intermediate f/stops.
Example: You are working with a 300mm lens with a minimum focusing distance
of 8'. Let's say you set an aperture of f/8. You notice a
small blooming cactus in the Sonoran desert and snap a few shots from
the car, while it is still far away--at infinity according to the distance
scale on the lens. You then walk closer until the subject is only 8'
away and take a second picture.
In the first photo, the cacti in the foreground are reasonably sharp,
at least recognizable; those that are behind your subject all seem quite
sharply rendered. In the close-up photo however, only your favorite cactus
is sharp. Those in the background are soft shapes of green without any
distinct lines and the foreground cacti are blurred away by the shallow
depth of field. In both cases, the farther they are from the focused point,
the less sharp they appear.
Remember: As you move closer or farther from any subject, two other factors
change as well: the size of the subject in the frame and the perspective.
The rendition of shapes and lines as well as the apparent distance between
objects will appear quite different at 100' than at 8', for
example. (This is visible in the viewfinder.)
·Set The "Right" Point Of Focus. As
a rule of thumb, DOF is distributed as follows at common shooting distances:
it extends about 1/3 in front of the point of focus and about 2/3 behind
it. Want lots of depth of field? Then set focus at a point roughly 1/3
of the way into a vast scene.
Especially when working with an autofocus SLR, it's tempting to
allow the camera to set the point of focus. While "shooting from
the hip" may be necessary to capture a fleeting moment of action,
it is important to control the exact point of focus when possible. That's
simple even with an autofocus camera--use focus lock while recomposing,
usually activated by slight pressure on the shutter release button.
Example: You are at a race track and notice three high performance cars
parked nearby: a black Porsche in the foreground, a red BMW farther back,
and a white Lotus in the background. You spot a celebrity leaning against
the nearest vehicle, his blue eyes clearly visible. You must now make
a decision. Do you focus on the BMW in the near midground to maximize
DOF, keeping all three cars reasonably sharp? Or do you carefully focus
on the person in the foreground so you'll have a razor sharp photo
of him to show your friends?
When a situation includes a well-defined object as the primary subject,
you will usually set focus for the most important point: the eyes in a
portrait, the lettering on the side of a yacht, or the petroglyphs on
a cave wall. DOF becomes a secondary consideration, although you do retain
some control as described in the other sections.
·Focus At The Hyperfocal Distance. There is a specific
point of focus which will produce maximum depth of field. Set focus at
exactly this "hyperfocal" distance: the nearest point which
will still keep a subject at infinity in adequately sharp focus. Now,
DOF will extend from half the focused distance all the way to infinity.
Naturally this differs depending on the aperture (f/stop) selected and
the focal length of the lens. However, the technique does allow you to
increase DOF without stopping down to minuscule apertures which would
create blur due to camera shake or subject movement.
There is a formula for calculating the hyperfocal distance to maximize
DOF, but it is rather complicated. You can find published charts listing
the hyperfocal distance for easy reference. The laminated card (for 35mm
camera owners) by Steve Traudt ($5.95, call (303) 245-6700) is but one
example. With a 50mm lens, for instance, the hyperfocal distance is approximately
as follows: 42' at f/8; 30' at f/11; 20' at f/16; and
15' at f/22.
Example: You are taking a picture of Times Square from a boulevard in
the center of the street with a 50mm lens. You want to render the entire
area sharply, but cannot stop down beyond f/11. (A smaller aperture would
require a long 1/30 sec shutter speed, which would blur the moving cars.)
Checking the chart, you set focus at 30', overriding the AF system
which wants to focus on the blonde in the foreground.
On the viewing screen, the image looks strange as much of it seems out
of focus. You take the picture anyway and find that everything from 15'
away to infinity is acceptably sharp in the resulting photo--within the
depth of field.
taken with telephotos often exhibit shallow depth of field,
leading some to believe that this is an inherent optical
property of long focus lenses. In fact that's a fallacy
as explained in the text, a concept well worth understanding.
(Tokina AF 400mm f/5.6 AT-X; at f/5.6; Elite 100.)
·Focus On Infinity
Only Rarely. Considering the information in the previous sections,
why would you ever focus on infinity? Well, I very rarely do so with land
or cityscapes, because: A) any foreground elements would be blurred (distracting)
and such secondary subjects are often important--adding a three-dimensional
effect to a two-dimensional photo, and B) most of the DOF would fall behind
infinity, providing no real value, "wasting" depth of field.
However, infinity focus can be useful in sports, motor racing, and wildlife
photography where the subject is located at a great distance. In these
situations, you can live with some partially blurred elements in the frame--if
any are included--because your primary goal is to produce an absolutely
razor sharp subject.
·Preview Depth Of Field. Some--but not all--SLR
(Single Lens Reflex) cameras from 35mm to medium format include a depth
of field preview button. Also called a "stop down" control,
it stops the lens diaphragm down to the actual "working" aperture
selected. This is required for visually estimating depth of field, because
otherwise, you always view the scene at maximum aperture with modern cameras.
Press the DOF Preview button and you can view the scene at f/8, f/11,
or f/22--with an ability to estimate which parts of the scene will be
very sharp, moderately sharp, and completely blurred away. Naturally,
the focusing screen will darken, becoming almost black at the smallest
apertures, unless the lighting is extremely bright. Before deciding that
this control is "useless," remember that your eyes will adjust
to the lower light level with time.
Stop down gradually, to f/4 then to f/5.6, and so on, moving to smaller
apertures slowly as your pupils open wider, improving low-light vision.
Granted, at f/22 on a heavily overcast day, DOF Preview may indeed be
of little value: the screen will be so dark that it is impossible to estimate
the zone of acceptable sharpness. In nature close-up photography, shine
a flashlight on the subject as a focusing aid. In more common circumstances,
at least with apertures no smaller than f/11, such precautions should
not be necessary.
Remember however that any visual assessment of depth of field is an estimate
and not a scientific technique. For example, a foreground swan which looked
sharp on the tiny viewing screen may appear quite blurred in a 16x20 print.
Nonetheless, particularly in high magnification photography, (with macro
or telephoto lenses) DOF Preview is a valuable tool. Especially when the
zone of acceptable sharpness is very shallow, it is important to asses
DOF at several apertures and points of focus--first on the pistil and
then on the stamen, for example. This technique will help to create technically
Example: When shooting with an 80-200mm f/2.8 zoom at 200mm, you set f/8
for correct exposure when taking an environmental portrait of a blacksmith
shoeing a horse at a pioneer village. You're shooting quickly to
capture the instant when the hammer impacts the nail. When your prints
come back from the processor, the outline of a green Land Rover roof in
the background is readily identifiable, while a partially blurred baseball
cap intrudes in the foreground. Of course, neither was visible while you
were viewing the scene at f/2.8, but both are serious distractions in
the image made at f/8.
To avoid disappointments of this type, especially with telephoto focal
lengths, use the depth of field Preview control. This is always useful--unless
shooting at the lens's maximum aperture, the only time that DOF
is accurately depicted without Preview.
·Check The DOF Scale On The Lens. Frankly, some
photographers admit to serious difficulties in assessing DOF visually.
Others simply do not find this technique adequately reliable or accurate.
If you fall into either category, learn to read the DOF scale on lenses
which include such markings. These days, many do not, while those found
on some zooms are inadequate or poorly designed: they tend to be difficult
(or impossible) to decipher for any given focal length/aperture combination.
Nonetheless, if your lens includes suitable markings, set focus first
and decide on an aperture which will probably provide adequate depth of
field. Now glance at the two f/numbers (on the scale) for the selected
aperture. These will show the distance range (near and far) that will
be in acceptably sharp focus in the final image. If necessary, change
the focused distance. For an added measure of DOF, stop down to an f/number
one larger than the one you will likely require.
Example: You are lying on a sunny Cape Cod beach watching your daughter
who is 10' away building sand castles near the surf. Out on the
water a catamaran with a multicolored sail is approaching, its course
paralleling the shoreline. You focus on the sand castle and set your 50mm
lens to f/16 for plenty of depth of field. The DOF scale signifies that
everything from about 7' to 21' will be sharply rendered in
the photo at f/16.
Unfortunately, the boat is at least 100' away, so it will be rendered
as partly blurred. No problem. You simply adjust the focusing ring until
the "16" mark (designating f/16) to the left of center on
the etched scale lines up with the infinity symbol. Now glance over at
the "16" mark to the right. You'll notice it is at the
8' point on the distance scale. Focus at 8' and stop down
to f/22 for an extra measure of safety. In the final photo, the youngster
will appear very sharp, while the catamaran should be rendered adequately
sharp as well--unless a long (motion blurring) shutter speed was used.
Try this exercise with your own lens in hand until it becomes second nature.
Then it will be useful in any situation with any lens which is suitably
marked, allowing for precise control of depth of field.
·Consider Other DOF Factors. In addition to the
information provided so far, additional specifics about DOF are useful
in certain photographic situations. First, depth of field depends on a
subjective judgment. You may accept a certain degree of blurring as "still
sharp," while a more critical viewer may consider it "fuzzy."
Serious macro photographers should know that in high magnification close-up
work depth of field is quite evenly distributed. It is roughly equal behind
and ahead of the focused plane.
The degree of sharpness we perceive also depends on projection distance
with slides, and on the size of a print and the distance from which you
view it. The zone of acceptable sharpness diminishes as larger prints
are made. A foreground object which appears to be in focus in a 4x6 snapshot
may look blurred in a 16x20 print or even in a 8x10 if viewed from very
All of the distances mentioned in this article relate to photography with
35mm equipment. In larger film formats, the concepts are identical but
depth of field is actually less at the same aperture and identical subject
distance. That's because larger formats require longer focal lengths
to fill the frame from the same shooting position. For example, a 105mm
lens in a 35mm system equals a 200mm lens on a 6x6cm (21/4" square)
medium format camera and a focal length of 360mm if working with 4x5 equipment.
The longer lenses required to produce the same image size (at the same
subject distance) produce a narrower zone of acceptably sharp focus.
This is one reason why some 4x5 landscape photos are made at f/32 and
even at f/64. However, the tilt/shift abilities of a view camera can also
be used to increase DOF at wider apertures. This feature allows the film
plane to remain parallel to the subject because the lens can be moved
off-axis. A similar technique is possible with certain Perspective Control
and Tilt/Shift lenses in 35mm equipment as well.
In addition to hyperfocal charts, you will find full DOF charts in some
published material, including some lens Owner's Manuals. These allow
the photographer to quickly predetermine the depth of field at any aperture
with specific focal lengths, at each of several focused distances.
Conclusion. When combining all of the information provided,
you can intelligently decide on how to achieve the exact depth of field
desirable in any specific situation. That may be shallow in a portrait--to
blur away clutter or extraneous elements which would compete for viewer
attention. Or it may be extensive as in a classic landscape--maintaining
sharpness in the foreground fence, midground horses, and the distant snow-covered
hills. Experiment, make notes, and review the photos afterward to confirm
you were on the right track.
Then read books which provide a more advanced coverage of the technical
factors. Become intimately familiar with "circles of least confusion,"
the differences in perspective at various camera-to-subject distances,
and the other "complicated stuff." The extra effort will be
worthwhile, if only for one reason: the ability to control depth of field
separates the snapshooter from the advanced photographer.