ExpoAperture2 Manual (Imperial/Standard) - English

Transcription

expoaperture
Depth-of-Field Guide Manual
www.expoimaging.net
2
ExpoAperture2 Depth-of-Field Guide Manual
V 1.0
Preface
The original ExpoAperture Depth of Field Guide was introduced over 20 years ago.
Primarily designed to be used with 35mm and medium format film cameras, the original
Guide used a fixed circle-of-confusion to make the necessary depth-of-field calculations.
Although the two formats required different circle-of-confusions, calculations were easily
converted between the two formats through a simple mental calculation. This was possible
because George A. Wallace, the inventor of the guide, selected a circle-of-confusion for
medium format (120) film that was approximately twice that of 35mm film. The original
guide used 35 microns as the circle-of-confusion for 35mm film – the upper limit in most
calculations. Wallace, a student of Ansel Adams, believed that the traditional circle-ofconfusion calculation for 35mm film (30 microns) was too exacting since it assumed that the
final print enlarged from a negative would be viewed at a distance equal to its diagonal
dimension. This would mean that an 8" x 10" print would be viewed at a distance of
approximately thirteen inches. Wallace's opinion was that the final print would be viewed at
a more comfortable distance – twenty inches for an 8" x 10" print. This theory is also
upheld in Alfred A. Blaker's book, Applied Depth of Field. Blaker demonstrates, through
various calculations, that the most comfortable viewing distance of a print or projected
image is twice the long dimension. In Blaker's explanation an 8" x 10" print would also be
viewed at a distance of twenty inches. The point of the foregoing explanation is that the
determination of the value of the circle-ofconfusion used in depth-of-field calculations,
although based on a mathematical formula, is somewhat subjective based on the
photographer's preferences and intended use.
Additionally, many changes in photography have occurred in the intervening period from
1980 to now, not the least of which is the transition to digital and its myriad different sensor
sizes. As a result, it is no longer possible to use the original guide with its fixed circle-ofconfusion to perform depth-of-field calculations for all the formats (film and digital) on the
market today because of the need to use different values for each different sensor or format
size. Today's photographers asked us to address these issues and to redesign the guide to
make it more flexible for modern day use and reduce or eliminate the need for mental
calculations.
In the middle of 2006, ExpoImaging began such a redesign. Wallace died in 2001, leaving
many incomplete notes on the design of the original guide, requiring us to reverse engineer
the guide to determine how it worked. Once we discovered the "secret" of his calculations,
it was just a matter of modifying the design of the guide to make calculations based on a
variable circle-ofconfusion – one that could be based on a photographer's preferences or
on the sensor size of a camera. The result is the ExpoAperture2 Depth of Field Guide.
George W. Ziegler, Jr.
Morgan Hill, California
March, 2007
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Table of Contents
1. - An Introduction to Depth-Of-Field - 4
1.A. - Focus as a Compositional Tool - 4
1.B - Controlling Depth of Field - 5
1.C - Image Sharpness - 6
1.D - Permissible Circle-of-Confusion - 7
1.E - The Advent of Digital Cameras - 9
1.F – Conclusion: Taking Advantage of Depth-of-Field in Your Photography - 10
2. - Using the ExpoAperture2 Depth-Of-Field Guide - 11
2.A - Distance Dial - 11
2.B - Focus Zone Dial - 11
2.C - Focal Length Dial - 11
2.D - f/stop and Circle-of-Confusion Dial - 12
2.E - Determining The Correct Aperture and Focal Point - 15
2.F - Determining Depth-of-Field for a Given Aperture and Focal Distance - 16
2.G - Determining Hyperfocal Distances - 16
2.H - Setting Apertures for Lenses with Focal Lengths Greater than 135mm - 17
2.I - Close and Macro Photography - 19
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1. - An Introduction to Depth-Of-Field
"There is nothing wrong with your television set. Do not attempt to adjust
the picture… We can reduce the focus to a soft blur, or sharpen it to crystal
clarity..."
The Outer Limits
Opening narration, The Control Voice, 1963-1965
The human eye is marvelously flexible and adaptive. It can adjust its focus so rapidly that
the impression is given that its entire field of view is in sharp focus when only a small
portion is actually in focus at any one time.
A camera lens, in contrast, freezes the focus on the image plane the instant the shutter is
released, preserving forever whatever the lens has rendered in or out of sharp focus. A
viewer of a photograph can immediately discern the different areas that are in sharp focus
and those that are not.
The distance between the nearest and furthest points from the camera at which everything
appears sharp is termed the depth-of-field. In many types of photography, such as
landscape photography, it is desirable to have the entire image as sharp as possible. In this
case the photographer may focus on the hyperfocal distance to obtain the maximum depthof-field possible. In others, the creative use of depth-of-field can be used to isolate elements
that the photographer may wish to emphasis or deemphasize. This opens the photographer
to the possibility of using selective focus (the ability of lenses to render some objects within
a scene in focus while others appear out of focus), as a compositional tool.
1.A. - Focus as a Compositional Tool
All photographers know that they need to focus their cameras, but only skilled
photographers know how to use selective focus as a compositional tool. Selective focus can
be used compositionally in two ways, to direct attention to the subject, and to eliminate
distractions.
Directing attention – In a photograph, a viewer's eye is irresistibly drawn to the area of sharpest
focus. It follows that a photographer who can control focus can also control the viewer's
attention. Sharp focus implies that the photographer is placing emphasis on an area for a
specific reason. In addition, elements that are in sharp focus are united by their similarity,
which separates them from the other out-of-focus elements. Consequently, the creative use
of focus can help build and support visual relationships.
Eliminating distractions – Often, either the foreground or background elements of a scene
detract from the main subject, directing the viewer's eye away from the photograph's center
of interest. When such areas are purposefully thrown out-of-focus, they are less likely to
distract the viewer. In some cases, a slight softness is all that is necessary. In other cases,
the effect may need to be exaggerated. The photographer needs to make the appropriate
compositional decisions based on the circumstances and his or her intent.
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Hyperfocal distance – In landscape photography in particular, photographers want as much of
the picture in sharp focus as possible. In the 1920s, such notables as Ansel Adams and
Edward Weston, along with several other photographers of the time, started the "Group
f64" which was dedicated to making photographs as sharp as possible throughout. The
group met only a few times and held only three shows, the first at the de Young Memorial
Museum in San Francisco. The term f64 evidentially arose from the smallest aperture setting
marked on large format lenses of the time, associating the use of this aperture with the
sharp, clear pictures prized by the group.
The group’s choice of f64 was symbolic, however, to the extent that the smallest aperture
does not always provide the largest depth-of-field. Instead, focusing your lens on the
hyperfocal distance with the correct aperture, you will maximize depth-of-field in your
image. The hyperfocal distance is the distance setting at a given aperture and focal length
that creates the most depth-of-field. The ExpoAperture Guide provides the ability to
determine hyperfocal distances (see Section 2.G, “Determining Hyperfocal Distances.”)
A photographer who is unaware of how selective focus can be put to use in composing an
image is likely to select any lens, shutter speed and aperture setting that will produce a good
exposure. While this approach may be necessary in some circumstances, skilled
photographers will never take a photograph without first deciding which areas of a scene
they wish to be in sharp focus and which ones should not. Although the extent to which
selective focus is used or is not used in a particular image is a creative decision,
implementation is a technical matter accomplished by controlling a lens' depth-of-field.
1.B - Controlling Depth of Field
The optical characteristics of lenses that permit control over depth-of-field are lens aperture,
lens focal length, and focusing distance. These characteristics are the primary variables in
depth-of-field calculations. It is not necessary to understand depth-of-field formulas in
order to understand the relationships these variables have with one another. This
understanding is enough to allow you to use depth-of-field creatively. The accompanying
ExpoAperture2 Depth-Of-Field Guide will do the calculations for you, allowing you to
concentrate on the aesthetic elements of your image.
Aperture – Every serious photographer understands that the size of the lens diaphragm
(aperture setting) affects depth-of-field. The ability to set the aperture is present in all but
the simplest cameras. Specifically, the smaller the aperture (the larger the f/stop number),
the more depth-of- field obtained, and, conversely, the larger the aperture setting (the
smaller the f- stop number), the less depth-of-field obtained. In most situations, the f/stop
selected for use will noticeably affect the image's appearance in the final photograph.
Focal length – The longer the focal length used, the less depth-of-field obtained, and,
conversely, the shorter the focal length used, the more depth-of- field obtained. Like the
f/stop selection, the selection of a different focal length will affect the image's appearance in
the final print.
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Focusing distance – Some lenses have markings on their barrels that indicate the distance at
which the lens is focused. Some fixed focal length lenses may also have depth-of-field
indicator lines that show a range of distances determined by the lens' manufacturer that will
be rendered in sharp focus when the lens is set at a particular f/stop. Almost all variable
focus length lenses (zoom lenses) do not have depth-of-field markings. If your lens has
depth-of-field markings, you will see that as the focus distance is brought closer to the lens,
the depth-of-field at any particular aperture setting diminishes. On the other hand, as the
focus distance is set further away from the lens, the depth-of field increases. Therefore,
moving the camera closer or further away from the plane of critical focus (or focus point)
can control the depth-of-field.
Therefore, the primary ways to control the depth-of-field are:
To increase the depth-of-field:
1) use a smaller aperture; or
2) use a shorter focal length; or
3) move further away from the plane of critical focus.
To decrease the depth-of-field:
1) use a larger aperture; or
2) use a longer focal length; or
3) move closer to the plane of critical focus.
Obviously, you can use any one of these methods or a combination of several of them to
achieve your desired result.
1.C - Image Sharpness
Depth-of-field and image sharpness are not the same thing. Depth-of-field is the range of
sharp focus produced by the combination of lens aperture, lens focal length and focusing
distance. These are theoretical values derived from optical formulas that assume a
theoretically ‘perfect lens’ with one element that is free from all aberrations and distortions,
and that focus precisely. In other words, depth-of-field calculations assume that the lens is
capable of delivering the degree of sharpness corresponding to the chosen circle-ofconfusion desired in the final print. [Note: The determination circle-of-confusion to be used
will be discussed later in Section 2.D.]
Real world lenses differ from the theoretically perfect lens used in depth-of-field calculations
in at least four significant ways. First of all, most lenses have aberrations, which are more
evident when the lens is set to large aperture openings. Spherical aberrations prevent the
lens from converging the incoming light rays on a single point, resulting in focusing errors.
Chromatic aberrations focus light of different wavelengths (colors) at slightly different
angles. Secondly, the lens must be able to focus precisely, i.e., there cannot be any defects in
the lens' focusing mechanism. Thirdly, real world lenses almost always have more than the
perfect lens’ one element. Finally, at very small aperture settings the sharpness of the image
is influenced by diffraction as light rays pass by the diaphragm. It is generally accepted that a
lens performs at its best when it is stopped down two to three full stops from its largest
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aperture setting. For an f/2.8 lens this would be f/5.6 or f/8. Therefore, using a smaller
aperture, like f/16 or f/22 to improve depth-of-field may actually decrease sharpness in your
photos.
The most common reason for lack of sharpness in photographs is camera movement, or
what is commonly referred to as motion blur. You can usually assume that camera
movement reduced sharpness in a photograph when nothing in the image is in focus. If you
had a steady camera and did a reasonably good job of focusing, at least some part of the
photograph should be in focus.
To reduce camera movement, use a tripod. If you are unable to use a tripod, the faster your
shutter speed, the more likely you will be to avoid motion blur. As a rule of thumb, your
shutter speed should be set to at least one over the focal length of the lens you are using. For
example, if you are using 250mm lens, your shutter speed should be set to 1/250 of a
second. When possible, you should also brace yourself against a tree or wall to improve your
steadiness. For really large enlargements of your images, this may not be enough. When
handholding or using a tripod remember to press the shutter slowly, or even better, use a
cable release with your tripod. Use mirror lockup, if available, so the camera doesn't vibrate
when the mirror snaps up in order to take the picture. Following these guidelines should
result in tack sharp images.
If you are using a digital camera with a LCD viewing screen it will be nearly impossible to
tell if your picture is sharp or not by quickly looking at the LCD. Nearly everything on the
LCD appears in focus because of its small size. If you have a zoom feature that you can use
during playback, magnify the image as large as possible and then examine the areas that need
to be in critical focus to confirm they are as sharp as you want them to be.
Finally, the introduction of image editing software like Adobe Photoshop® also changes
whether portions of a photograph, and the photograph as a whole, are more or less sharp to
the viewer. A complete discussion of the merits of post-processing sharpening are beyond
the scope of this manual. However, suffice it to say that, just as with all other aspects of
photography, there are numerous creative and quality benefits to be gained by capturing in
camera an image as close as possible to your intended print.
1.D - Permissible Circle-of-Confusion
In optics, a circle-of-confusion is a slightly out-of-focus point of light. A perfect lens when
focused on a point of light like a distant star would render it sharply on the image plane – as
a point of light. Since a lens can only render one plane in focus at a time, points of light that
are either closer or further away from the lens than our subject would be out-of focus.
Slightly out- of-focus, the points would appear as tiny circles. The permissible circle-ofconfusion is the largest that this circle can be and still appear to be sharp to the eye at a
normal viewing distance. Circles smaller than the permissible circle-of-confusion will always
appear sharp.
In order to determine the permissible circle-of-confusion we need to start with the final
product – the enlarged print. You may well ask, "Why start here?" The reason we are
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starting with a discussion of the circle-of-confusion present in the final print is because it is
the most subjective of the variables and depends on factors outside of the camera, in
particular the photographer's visualization.
In determining the circle-of-confusion, prints are considered to be viewed at a distance equal
to their diagonal dimension. In actuality, prints are viewed from distances further away. An
8" x 10" print has a diagonal of 12.8 inches. Unless you are scrutinizing the print very
closely an actual viewing distance of 14 or 15 inches is more practicable. You can observe
this type of viewing behavior in museums where a person stands back from a painting to
take in the whole view and occasionally moves in closer to look a specific element and then
moves back to the original view position.
There are several ways to determine the permissible circle-of-confusion. One way is based
on normal human visual acuity. The resolution of the human eye in a person with normal
visual acuity is generally assumed to be 5 lines per millimeter when viewed at a distance of 25
centimeters. Twenty-five centimeters is roughly 10 inches, the diagonal dimension of a 6" x
8" print. Therefore along the 25 centimeter dimension the viewer could discern 1,250 lines
or points (5 x 25 x 10). The circle-of-confusion would be 0.200mm (250mm divided by
1,250.) Given this information the circle-of-confusion in an 8" x 10" print would be
approximately 0.250mm since the 8" x 10" print is larger by a factor of approximately 25%.
Another method assumes that the circle-of-confusion is equal to 1/100th of an inch in an 8"
x 10" print. 1/100th of an inch is equal to 0.254mm. Since these methods are so close, and
the second may have derived from the first one, we will use 1/100th as the permissible
circle-of-confusion in further discussions.
The traditional value for the circle-of-confusion for 35mm film has been 30 microns. The
30 microns is based on using a 1/100th of an inch circle-of-confusion in an 8" x 10" print.
The 30 microns is calculated by dividing the 0.254mm circle-of-confusion desired in the final
print by the number of times the negative needs to be enlarged to make the print. In this
calculation we are assuming that the negative will be enlarged only as many times as
necessary to fill the 8" x 10" print format or 8.47 times (the 203mm print dimension [or 8"
dimension] divided by the 24mm film dimension). The required Circle-of-Confusion
necessary in the negative is 0.030mm (0.254 divided by 8.47) or 30 microns.
These calculations reveal two critical factors in determining the circle-of-confusion to use
when making an image: 1) the viewing distance of the final print or projected image, since
the further away the image is viewed, the larger the permissible circle-of-confusion can be;
and 2) the number of times the image source needs to be enlarged to make the print or
project the image.
Adjustments to the calculations need to be made for cameras that capture images on film or
sensors that differ in size to 35mm film. In digital cameras, which generally use sensors
smaller than traditional 35mm film, the image needs to be enlarged more times. For
example an image taken with a Nikon DX sized sensor has to be enlarged 1.5 times more
(the crop factor) than 35mm film to make the same size image therefore you need to use a
20 micron (30 divided by 1.5) circle-of-confusion in your calculations.
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We have included a chart with the ExpoAperture2 Depth-Of-Field Guide which provides
the appropriate circle-of-confusion to use with your camera. Of course, you are free to use
any circle-of-confusion you wish depending on your desired final result.
1.E - The Advent of Digital Cameras
Unfortunately, the increased popularity of digital cameras has been accompanied by an
increase in misconceptions about their depth-of-field capabilities. These misconceptions
result in statements such as "the smaller the sensor the better depth-of-field" and "for the
same angle-of-view the depth-of-field increases by the crop factor of the camera."
Statements like these fail to emphasize the overall contributing reason that apparent depthof-field increases when using digital cameras, which is that manufacturers have had to
incorporate shorter focal length lenses on digital cameras in order to maintain the angle-ofview typically found in lenses traditionally used for 35mm film, called ‘normal’ lenses.
Compact digital cameras have extremely small sensors, typically 2/3 of an inch to ¾ of an
inch. To compensate, the camera manufacturers use equally as short focal length lenses,
often in the range of 7mm to 9mm. Most of them do not have f/stops greater than f/8.
With these short focal length lenses set at f/8, nearly infinite depth-of-field is achieved. As a
result, achieving any sort of creative depth-of-field control with these cameras is virtually
impossible.
Normal lenses are lenses with focal lengths that approximate human vision perspectives.
With 35mm film or "full frame" digital cameras, the typical normal lens is 50mm – a 40
degree angle- of-view. On digital cameras with a 1.5x crop factor, as an example, a normal
lens with a 40 degree angle-of-view would be approximately 33mm. On a medium format
film camera a normal lens would be 75-80mm. Therefore the smaller sensor size, in and of
itself, has little to do with the better depth-of-field. The apparent better depth-of-field is
almost entirely the function of the shorter focal length lenses.
The basic rules of depth-of-field, which are based on lens optics, have not changed just
because of the introduction of digital sensors. Only the difference in digital sensor size
versus 35mm creates a difference in depth-of-field results. The truth of the matter is that
the same focal length lens and aperture setting when used on a 35mm camera and on a
digital camera will produce the same depth-of-field, when the resulting image is enlarged the
same number of times. Because images from digital cameras require greater enlargement to
achieve the same print size, the enlarged image from a digital camera will actually have less
depth-of-field given the same focal length and aperture. To have the same depth-of-field,
the circle-of-confusion needs to be smaller. The correct circle-of-confusion can be quickly
calculated by dividing 30 microns by the digital camera's crop factor. Therefore to achieve
the same depth-of-field, because of the required smaller circle-of-confusion, you need to use
a shorter focal length lens or smaller aperture.
Fortunately most digital camera manufacturers use shorter focal length lenses in order to
compensate for the angle-of-view necessary to approximate the normal lenses used on
35mm cameras. However this has a tendency to over-compensate since changes in focal
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length are handled exponentially in depth-of-field calculations. Depth-of-field changes
cannot be computed using a linear variable such as the crop factor of the camera.
1.F – Conclusion: Taking Advantage of Depth-of-Field in Your Photography
Depth-of-field can be used creatively to emphasize or deemphasize elements in your
photographs. If you are attempting to achieve overall image sharpness, focusing on the
hyperfocal distance maximizes depth-of-field from the closest possible distance to infinity.
The exclusive variables photographers can use at capture to control depth-of-field are lens
focal length, lens aperture and focusing distance. By changing any one or all of these
variables, you can change the depth-of-field.
The complexity of depth-of-field calculations can make taking advantage of depth-of-field
when shooting difficult. In the past, to figure the correct f/stop to use, determine your focus
point or figure out what depth- of-field you were actually getting you needed to carry around
reams of lens and f/stop tables or make your best guess.
The accompanying ExpoAperture2 Depth-of-Field Guide eliminates the inconvenience of
carrying around those tables, doing mathematical calculations or guessing incorrectly. The
Guide quickly solves depth-of-field calculations, freeing you to focus on the creative aspects
of your shots.
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2. - Using the ExpoAperture2 Depth-Of-Field Guide
The ExpoAperture2 Depth-of-Field Guide consists of several color-coded dials which can be
set to quickly perform depth-of-field calculations. The Guide enables you to easily
determine how to set your camera to achieve a desired depth-of-field, to determine what
depth-of-field you will achieve given your chosen camera settings, or to determine the
hyperfocal distance.
2.A - Distance Dial
The Distance Dial is used to determine the focal point and
the range of distance around the focal point that is in
focus.
The dial is divided into fifteen segments or “zones,” each
represented by an alternating gray or white segment. The
distances that fall exactly on the boundaries of the zones
are printed in red. Other distances are represented by
hash marks and their respective values. The outer portion
of the dial contains the distances from two feet to infinity.
The inner portion contains distances from twelve inches
to two feet.
2.B - Focus Zone Dial
When matched up with the appropriate f-stop the Focus
Zone Dial is used to determine how many zones are in
focus. There are roughly nine zones represented on the
dial by the alternating light and dark gray areas. Each
alternating gray area represents one zone and is the
equivalent of one zone on the Distance Dial. The dial also
contains a window for setting the focal length of the lens
being used using the Focal Length Dial.
2.C - Focal Length Dial
The yellow Focal Length Dial is located under the Focus
Zone Dial. The focal lengths on the dial range from 15mm
to 135mm. Rotate the Focal Length dial to set the Circle-ofConfusion, sensor size or film format.
After setting your sensor size on the Circle-of-Confusion
Dial, hold the Circle-of-Confusion stationary with one hand
and select the focal length of the lens by rotating the Focus
Zone Dial with your other hand, until the correct focal
length shows in the window.
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The following chart shows the focal length of the lens markings on the dial.
Focal Length Dial Markings
15
15mm
45
45mm
●
16mm
50
50mm
●
17mm
●
55mm
18
18mm
60
60mm
20
20mm
70
70mm
●
22mm
●
75mm
24
24mm
●
80mm
28
28mm
85
85mm
●
30mm
●
90mm
35
35mm
●
100mm
●
40mm
105
105mm
●
42mm
●
120mm
45
45mm
135
135mm
2.D - f/stop and Circle-of-Confusion Dial
This dial contains two scales, one scale for the f/stops(blue)
and one for the circle-of-confusion(green).
The f/stop scale is calibrated in ⅓ stop increments from f/1
to f/64. It is used in conjunction with the Focus Zone Dial
to determine the number of zones in focus at a particular
f/stop or the f/stop to use in order to obtain the desired
number of zones in focus.
The Circle-of-Confusion, sensor size, or film format is set
using the green portion of the dial and by rotating the Focal
Length Dial until the correct setting shows through the cutout.
The following charts show sensor sizes and film formats for many popular makes and
models of cameras. If your camera is not included on this chart, please refer to your
camera’s manual which should include the sensor format or film size in the specifications
section.
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Camera Sensor and Film Format Circle of Confusion Reference Chart
Digital Cameras and Backs:
Camera
Manufacturer
Canon
Contax
Epson
Fujifilm
Camera Model
EOS 5D
EOS-1Ds MarkII
EOS-1Ds
EOS-1D Mark III
EOS-1D Mark IIn
EOS-1D Mark II
EOS-1D
EOS 10D
EOS 20D, EOS 20Da
EOS 30D
EOS D30, EOS D60
EOS Digital Rebel (300)
EOS Digital Rebel XT (350D)
EOS Digital Rebel XTi (400)
N Digital
R-D1
FinePix S5 Pro
FinePix S3 Pro
FinePix S2 Pro
FinePix S1 Pro
DCS SLR/c
DCS SLR/n
DCS 14n
DCS ProBack 645
Kodak
Konica Minolta
Leica
Nikon
Olympus
Panasonic
Pentax
Samsung
Sigma
Sony
1
2
3
4
3
DCS ProBack Plus
Crop
Factor
Suggested CoC
1
in Microns
1.0
30
1.3
23
1.6
use 1.6x setting
1.0
1.5
30
20
1.6
use 1.6x setting
1.0
30
1.3
23
1.6
use 1.6x setting
1.5
20
1.3
1.4
23
use APS-C setting
1.5
20
2.0
17
see note 2
3
3
DCS ProBack
DCS 760
DCS 660
DCS 720x
DCS620x
Maxxum 5D
Maxxum 7D
M8
DMR
D200
D80
D2X, D2Xs
D100
D70, D70s
D50
D40
D2H, D2Hs
D1, D1H, D1X
EVOLT E-500
EVOLT E-400
EVOLT E-330
EVOLT E-300
E-1
LUMIX DMC-L14
K10D, K110D, K100D
ist DL2, ist DS2
*ist DS, *ist D
GX-10, GX-1L, GX-1S
DP1
SD14, SD10, SD9
DSLR-A100
DSC-R1
2.0
4:3 - 17
3:2 - 15
16:9 -13
see note 4
1.5
20
1.5
20
1.7
17
1.5
1.7
20
17
As based on a 0.254mm Circle of Confusion in an 8” x 10” enlargement of the captured image. See the main text in the
ExpoAperture2 Depth of Field Manual for a detailed description concerning the Circle-of-confusion calculation.
The aspect ratio of Olympus cameras is 4:3 rather than 3:2, as a result you can use a 17 micron Circle-of-confusion rather
than 15 microns as suggested by the crop factor.
Kodak digital backs are capable of making 5:5, 4:5 or 5:4 aspect ratio images.
The Panasonic Lumix camera is capable of making images in 4:3, 3:2, or 16:9 aspect ratios. Depending on the aspect ratio
selected use 17 microns, 15 microns, or 13 microns, respectively, for the Circle-of-confusion.
Film Formats:
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Format
35mm half frame
APS-C
35mm full frame
6 x 4.5 cm
6 x 6 cm
1
2
Aspect
Ratio
Suggested CoC
in Microns
2
0.75:1
1.5:1
1.5:1
1.3:1
17
use APS-C setting
30
52
2
1.0:1
56
Type of Film
135
Advanced Photo System (APS)
135
120, 220, or 620
120, 220, or 620
As based on a 0.254mm Circle of Confusion in an 8” x 10” enlargement of the captured image. See the main text in the
ExpoAperture2 Depth of Field Manual for a detailed description concerning the Circle-of-confusion calculation.
Kodak stopped producing 620 film in 1995, but it is possible to wind 120 film stock onto a 620 spool in a darkroom to enable
the use of cameras that can accommodate 620 film.
The following chart shows the range of full and fractional f/stops as they appear on the dial.
Not all cameras number the fractional f/stops as shown.
f/stops included on Aperture Dial
Apertures
in full
stops
f/1
f/1.4
f/2
f/2.8
⅓ stops
f/1
f/1.2
f/1.3
f/1.4
f/1.6
f/1.8
f/2
f/2.2
f/2.5
f/2.8
f/3.2
f/3.5
Apertures
in full
stops
f/4
f/5.6
f/8
f/11
⅓ stops
f/4
f/4.5
f/5
f/5.6
f/6.3
f/7.1
f/8
f/9
f/10
f/11
f/13
f/14
Apertures
in full
stops
f/16
f/22
f/32
f/45
f/64
14
⅓ stops
f/16
f/18
f/20
f/22
f/25
f/28
f/32
f/37
f/41
f/45
f/52
f/58
f/64
V 1.0
2.E - Determining The Correct Aperture and Focal Point
Use the following method to determine the correct aperture and focus settings for a specific
depth-of-field. Your camera should be in Aperture Priority mode and, unless your subject is
at the computed focal point, your camera should be in manual focus mode so that you can
manually focus at the correct distance.
EXAMPLE:
The photographer is using a 35mm film camera with a 50mm lens and wants a depth of field
of 6’ to 30’. What aperture should the photographer use to achieve this depth-of-field?
STEP 1 –
On the Guide’s Distance Dial find the distance range that
you would like to be in focus, in this example, 6’ to 30’.
STEP 2 –
Count the number of Focus Zones contained within the
range of distances you have selected. Each alternating grey
and white arc represents one zone. Here, the range of
distances covers 4 zones.
STEP 3 –
Note the distance at the center point of the Focus Zones
you have selected. In this case, you will find 10 feet at the center of the 4 zones you found
in Step 2. This point is called the point of critical focus, and it will be the focal distance to
which you will want to set your lens to achieve the desired depth-of-field.
STEP 4 –
Turn the guide over and set the Focal Length Dial to
the correct format or desired circle-of-confusion that
you wish to use -- here, 35mm film or 30 microns -by turning the dial until the correct value appears in
the cutout on the Focus Zone Dial.
STEP 5 –
Rotate the Focus Zone Dial of the guide to expose
the focal length of the lens you are using through the
small window labeled “FL – mm,” here, 50 mm.
STEP 6 –
Find the aperture (f/stop) above the number of Focus Zones you determined in Step 2 (4
zones). f/18 is the aperture located directly above 4 zones, therefore, in order to achieve a
depth-of-field of 6’ to 30’ in this example, the photographer would set his 35mm camera to
f/18 when shooting at a 50 mm focal length.
15
V 1.0
2.F - Determining Depth-of-Field for a Given Aperture and Focal Distance
Use this method to determine your depth-of-field when your camera is set to a specific
aperture and you know your focal distance.
EXAMPLE:
The photographer is using a digital SLR camera with a 1.5x crop factor, a 45mm lens
stopped down to f/11 and is focusing on a subject that is 7½ feet away. What is the
resulting depth-of-field given this photographer’s settings?
STEP 1 –
Set the Focal Length Dial to the correct format or desired circle-of-confusion that you wish
to use. In this example, the photographer is using a 1.5x or 20 microns circle-of-confusion.
STEP 2 –
Rotate the Focus Zone Dial of the guide to
expose the focal length of the lens you are using
through the small window labeled “FL – mm.”
Here, the photographer is using a 45mm focal
length.
STEP 3 –
Note the number of Focus Zones (2 zones)
under the aperture (f/stop) to which you have
your camera set, in this case f/11.
STEP 4 –
Turn the Guide over. On the Guide’s Distance Dial
find the focal point of your lens, in this case, 7½
feet.
STEP 5 –
Each alternating gray or white arc represents one
zone. From Step 3, you have 2 zones in focus, one
on either side of your 7 ½ foot focal zone. The
numbers above the sides of these 2 zones represents
the depth-of field the photographer will achieve, 6’
to 10’.
2.G - Determining Hyperfocal Distances
Hyperfocal distance is the distance setting that produces the greatest depth-of-field for any
given aperture. Knowing the hyperfocal distance of the particular camera/lens setup is
particularly useful in landscape photography where the photographer may want the
photograph in focus from the nearest possible distance to infinity. Using this method you
can determine the hyperfocal distance.
16
V 1.0
EXAMPLE:
A photographer is using a Medium Format film camera that produces a 6 x 4.5 cm image
and an 85mm lens stopped down to f/22. What is the hyperfocal distance for the
photographer’s shot?
STEP 1 –
Set the Focus Length Dial to the correct format or
desired circle-of-confusion that you wish to use, in this
case, 6 x 4.5 or 52 microns.
STEP 2 –
Rotate the Focus Zone Dial to expose the focal length
of the lens you are using through the small window
labeled “FL – mm,” here, 85mm.
STEP 3 –
Note the number of Focus Zones under the aperture
(f/stop) to which you have your camera set. In this case, the
number 3 (representing three focus zones) is under f/22.
STEP 4 –
Turn the guide over. On the Distance Dial start at infinity
(∞) and going in a counter-clockwise direction count out the
number of Focus Zones determined in step 3 (3 zones),
noting the distance at which you end up, 10’.
STEP 5 –
Determine the mid-point of the distance you just counted out, in this case, halfway between
10’ and the ∞ symbol is 20’. This is the hyperfocal distance. When you focus your camera
at the hyperfocal distance of 20’, everything from 10’ to infinity will be in focus.
2.H - Setting Apertures for Lenses with Focal Lengths Greater than 135mm
Shooting with lenses of focal lengths greater than 135mm using the Standard ExpoAperture2
Depth of Field Guide requires a simple calculation to determine the required aperture setting
for your desired depth-of-field. Note that if you will frequently be shooting with lenses with
greater than 135mm focal length, ExpoImaging also makes a Telephoto version of the
ExpoAperture2 Guide which does not require additional calculations for these focal lengths.
First, find the smallest divisor of the actual focal length used that will result in a focal
length that falls on the Depth-of-Field Guide (in other words, a focal length less than
135mm). For example, if shooting with a 300mm focal length, the number to use is 3, since
300mm divided by 3 is 100mm, which is less than the maximum Aperture Guide focal
length of 135mm. Dividing 300mm by 2 will not work in this example, because 150mm is
greater than 135mm and does not fall within the focal length range available on the Aperture
Guide.
17
V 1.0
Next, divide the focal length by this number, and the minimum and maximum distances
you use on the Distance Dial by the square of this number, to bring them back to within
the usable range on the Depth-of-Field Guide.
Therefore, if shooting with a 300mm focal length lens, divide the focal length by 3 and the
distances by 9.
EXAMPLE:
Using a 200mm Focal Length Lens and a Depth-of-Field of 120' to infinity, use the Depthof-Field Guide to determine your necessary aperture setting using a 20 micron circle-ofconfusion (1.5x factor digital sensor).
STEP 1 –
Divide the 200mm focal length of the lens you are
using by 2 and set yellow Focal Length window to
the resulting focal length. 200mm divided by 2 =
100mm.
Set the focal length on the Depth-of-Field Guide to
100mm.
STEP 2 –
Divide the distance range required by 4 (2 squared)
and find those new distances on the Distance Dial.
(120' - ∞') divided by 4 = (30' to ∞'). Find the distances
of 30' to ∞' on the Distance Dial.
STEP 3 –
Count the number of depth-of-field zones (alternating
gray and white areas) within the distance range you
found in Step 2. There is 1 distance zone (gray area)
between 30' and ∞'.
STEP 4 –
Locate the number of zones for your desired depth-of-field on the front of the Guide to
find your aperture setting. Find the number 1 on the gray zone area on the focus zone dial.
RESULT:
f/27 (halfway between f/22 and f/32) is the aperture to use to get 1 depth-of field zone.
Therefore, use f/27 with a 200mm focal length to get a depth-of-field from 120' to infinity.
18
V 1.0
2.I - Close and Macro Photography
Setting the Aperture for a Depth-of- Field Ranging from 12”to 24”
The inside ring on the Distance Dial (white numbers a blue background) provides
measurements from 12” to 24” for close and macro shots. Use these measurements in the
standard manner (described previously for depth-of-field from 2’ to infinity) to find the
preferred aperture setting for your distance range. The following example takes you through
the procedure for determining depth-of-field between 12” and 24”.
EXAMPLE:
What aperture setting should a photographer use to have all subjects from 15” to 18” in
focus using a 35mm camera and a 50mm focal length?
STEP 1 –
On the Distance Dial’s blue ring, find the range of
distances that you would like to be in focus, this case, 15”
to 18.”
STEP 2 Count the number of zones within the distance range. The
alternating gray and white arcs each represent one depthof-field zone. There are 4 zones between 15” and 18”.
STEP 3 Find the middle of the number of zones in your range and set your camera’s focus distance
accordingly. On your camera, set the focus distance to the distance corresponding to the
middle of the 4 zones (2 zones on either side). In this example, the camera focus should be
set at 16.5 inches to get a depth-of-field of 15” to 18”.
STEP 4 –
Turn the Guide over and select a focal length of 50
mm on the Focus Zone Dial.
STEP 5 –
Find the amount of zones in your range on the front
of the Depth-of-Field Guide to get your aperture
setting.
The f/stop above the number 4 in the gray area on the
Focus Zone Dial indicates that f/18 is the largest
aperture capable of providing 4 depth-of-field zones
with a 50 mm lens. Therefore, a photographer
shooting with a 35mm camera at 50mm needs to shoot at f/18 to have a depth-of-field from
15” to 18”.
19
V 1.0
Bibliography
Blaker, Alfred A. (1985). Applied Depth of Field. Boston: Focal Press.
Carroll, John S. (Ed.). (1963). Photo-Lab-Index. (22nd lifetime edition). New York: Morgan
& Morgan.
London, Barbara … (et al.). (2005). Photography. (eighth edition, pp. 56-61). New Jersey:
Prentice Hall.
Stroebel, Leslie … (et al.). (2000). Basic Photographic Materials and Processes. (second edition,
p151-155). Boston: Focal Press.
Stroebel, Leslie, and Richard Zakia (Editors). (1993). The Focal Encyclopedia of Photography.
(third edition). Boston: Focal Press.
20
V 1.0
ExpoAperture2 Depth-of-field Guide Instruction Manual
Documentation version 3.0
PN: EXPOA02MAN
Copyright Notice
Copyright © 2007 ExpoImaging, Inc. All Rights Reserved.
The information contained herein is designed only for use with this ExpoImaging, Inc.
(“ExpoImaging”) product. Any technical documentation that is made available by
ExpoImaging is the copyrighted work of ExpoImaging and is owned by ExpoImaging.
NO WARRANTY ON DOCUMENTATION.
The technical documentation is being delivered to you AS-IS and ExpoImaging makes no
warranty as to its accuracy or use. Any use of the technical documentation or the
information contained therein is at the risk of the user. Documentation may include
technical or other inaccuracies or typographical errors. ExpoImaging reserves the right to
make changes without prior notice.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in
any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,
without the express written permission of ExpoImaging, Inc., 365 Woodview Avenue, Suite
700, Morgan Hill, California 95037-2840.
Trademarks
ExpoImaging, the ExpoImaging logo, ExpoDisc, ExpoCap, ExpoAperture, and
ExpoAperture Depth-of-field Guide are trademarks or U.S. registered trademarks of
ExpoImaging, Inc.
Other product names mentioned in this manual may be trademarks or registered trademarks
of their respective companies and are hereby acknowledged.
Printed in the United States of America.
10 9 8 7 6 5 4 3 2 1
21
V 1.0
ExpoAperture2 Depth-of-field Guide
Technical Support
ExpoImaging offers the following technical support options for help in using or
troubleshooting ExpoImaging products.
•
Online Service and Support
Connect to the ExpoImaging Support Web Site at http://expoimaging.net/support, select
FAQs and then select your product. In addition to answers for the most frequently asked
questions and instruction manuals, you can also post a question to an on-line Technical
Support representative. Or, you can contact us directly at [email protected].
•
Telephone Support
Call 1-408-778-2040 and ask to speak to one of our Technical Support representatives.
Limited Warranty on ExpoAperture2 Depth-of-Field Guide
WHAT IS COVERED: ExpoImaging, Inc. (“ExpoImaging”) warrants to the original retail
purchaser that the ExpoAperture Depth-of-field Guide covered by this limited warranty
statement conforms to the manufacturer’s specifications and will be free from defects in
workmanship and materials for a period of one (1) year from the date of original purchase.
For warranty service, you must provide proof of the date of original purchase.
WHAT WE WILL DO TO CORRECT PROBLEMS: Should your ExpoAperture Depthof-field Guide prove to be defective during the warranty period, please call ExpoImaging
Technical Support at (408) 778-2040 for warranty repair instructions and return
authorization. An ExpoImaging Technical Service representative will provide telephone
diagnostic to determine whether the product requires service. If service is needed,
ExpoImaging will exchange the product without charge. ExpoImaging will ship a
replacement product to you, freight prepaid. You are responsible for securely packaging the
defective product and returning it to ExpoImaging within ten (10) working days of receipt of
the replacement product. ExpoImaging requires a debit or credit card number to secure the
cost of the replacement product in the event you do not return the defective one. The item
replaced becomes ExpoImaging property. The replacement product may be new or
refurbished to the ExpoImaging standard of quality, and, at ExpoImaging’s may be another
model of like kind and quality.
WHAT’S NOT COVERED: This warranty covers only normal use. This warranty is not
transferable. ExpoImaging is not responsible for warranty should the ExpoAperture label or
logo be removed or should the depth-of-field guide fail to be properly maintained or fail to
function properly as a result of misuse, abuse, improper installation, neglect, improper
shipping, damage caused by disaster such as fire, flood, or service other than by
ExpoImaging.
THE WARRANTY AND REMEDY PROVIDED ABOVE ARE EXCLUSIVE AND IN
LIEU OF ALL OTHER EXPRESS OR IMPLIED WARRANTIES INCLUDING, BUT
NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY,
NON-INFRINGEMENT OR FITNESS FOR A PARTICULAR PURPOSE. SOME
LAWS DO NOT ALLOW THE XCLUSION OF IMPLIED WARRANTIES. IF THESE
LAWS APPLY, THEN ALL EXPRESS AND IMPLIED WARRANTIES ARE LIMITED
22
V 1.0
TO THE WARRANTY PERIOD IDENTIFIED ABOVE. UNLESS STATED HEREIN,
ANY STATEMENT OR REPRESENTATIONS MADE BY ANY OTHER PERSON
OR FIRM ARE VOID. EXCEPT AS PROVIDED IN THIS WRITTEN WARRANTY,
EXPOIMAGING, INC. SHALL NOT BE LIABLE FOR ANY LOSS,
INCONVIENIENCE OR DAMAGE. INCLUDING DIRECT, SPECIAL,
INCIDENTAL OR CONSEQUENTIAL DAMAGES, RESULTING FROM THE USE
OR INABILITY TO USE THE EXPOIMAGING PRODUCT, WHETHER
RESULTING FROM BREACH OF WARRANTY OR ANY OTHER LEGAL THEORY.
23

ExpoAperture2 Manual (Imperial/Standard) - English

Transcription

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