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Large, Fully Electronic
Mount System
Focus Preset
The conventional interface between
the lens and camera body was
With the focus preset feature, you
mechanical, with the use of engaging
can set the desired focusing distance
levers and gears. This method caused
in memory and later instantly focus
the lens at that distance. Normal
physical problems such as wear and
rattle. It was limited and more diverse
picture-taking and focusing are
information could not be exchanged.
possible even while focus preset has
Canon EF lenses do not use such
been set. At a soccer game, for
mechanical links at all. About 50
example, you can preset the focus
items of information are exchanged
for the goal. You can focus normally
as digital signals between the lens
while the player approaches the goal,
and camera in real time. This enables
then when the ball is shot into the
goal, you can obtain instant focus.
high-speed and high-precision
control. And since the lens mount
diameter is an ample 54mm, special
lenses such as large-aperture lenses
and TS-E lenses can be used. The EF
Fluorite (CaF2) and UD-Glass
mount is an advanced interfacing
system with infinite possibilities.
The refraction of light differs
depending on the wavelength.
Built-In Motor and EMD
The point of focus, therefore, differs
depending on the different
Canon EF lenses (except TS-E
wavelengths or colours. When the
and MP-E lenses) have a built-in
different wavelengths are focused
AF motor. Compared with camera
at different points, the colours look
body-based AF motors, lens-based
smeared. This is called chromatic
motors have driving energy with
aberration. The longer the focal
lower transmission loss. The optimum
length, the more pronounced
AF motor for the particular lens can
chromatic aberration becomes.
also be selected and installed. The AF
Usually, an achromatic element
operation is therefore quick, quiet, and
is used in a lens to correct chromatic
highly precise. The lenses also have an
aberration. However, normal optical
EMD (Electromagnetic Diaphragm)
glass can only be corrected for
to control the aperture electronically.
two primary spectral colours.
The aperture can be set either with
An exception to this limitation
an electronic dial or with the electronic
is Fluorite, an ideal material.
pulse signal sent according to the
Fluorite, which is crystalline, has
exposure reading. Aperture control
abnormally low refraction and low
precision is therefore unmatched.
dispersion characteristics, which
optical glass cannot achieve. It also
Ring-type USM
has anomalous dispersion from the
green to blue wavelengths. Canon
developed production technologies to
manufacture Fluorite. By incorporating
Fluorite in lenses, the points of focus
of the three primary spectral colours
of red, green, and blue all meet at one
point for ideal correction of chromatic
EMD
aberration. There is also UD-glass,
which is a special type of optical glass
Built-in motor and EMD
whose properties nearly match those
of Fluorite. The effect of two UD-glass
elements is equivalent to having one
Fluorite element. And one super
Inner Focusing and
UD-glass element gives almost the
Rear Focusing
same effect as one Fluorite element.
An inner focusing lens has the
focusing lens group(s) in front of
Comparison of optical characteristics
between optical glass and Fluorite
the diaphragm, while a rear focusing
lens has the focusing lens group(s)
behind the diaphragm. Both focusing
Red
systems allow the focusing lens group
Glass
to be small. This minimises the load
Blue
on the actuator which drives the
Anomalous
autofocus. In turn, the AF speed is
dispersion
faster. The whole optical system can
also be made more compact.
Red
Also, since the lens does not rotate
Blue
during focusing, the effects of a
Fluorite
circular polarising filter or gelatin
filter remain intact.
Fluorite and UD glass
21
Description of Lens Designation
The lens designations follow a standard format to identify the lens.
EF 75-300mm f/4-5.6 IS USM
Focal length:
Maximum aperture:
Special Function:
USM: Indicates
Indicates the focal
Indicates the lens's
Any special
that the lens uses
length range from
maximum aperture.
feature such as an
an Ultrasonic
the shortest to
(See below for
image stabilizer,
Motor for
longest length.
details.)
macro feature, etc.,
autofocusing.
(See below for
is indicated.
(See page 19 for
details.)
details.)
Focal Length
maximum aperture (the f-number
is larger) allows the lens to be
A focal length of 50mm is closest
more compact and light. Single
to what the eye sees. This focal
focal length lenses have only one
length is used as a reference point
maximum aperture while zoom
for lens categories. For example,
lenses may have two, one for each
lenses with a shorter focal length
end of the focal length range. For
are called wide-angle lenses, while
example, a EF 28-80mm f/3.5-5.6
those with a longer focal length
lens has a maximum aperture of
are called telephoto lenses. Single
f/3.5 at 28mm and f/5.6 at 80mm.
focal length lenses have only one
focal length, while zoom lenses
Aperture and Shutter Speed
have a range of focal lengths.
(When EF lenses are used with the
Under the same light level, if the
EOS IX, the focal length
aperture opening is made larger by
corresponds to 1.25 times that
one step, the shutter speed can be
indicated for 35mm cameras.)
increased by one step. For example,
if an aperture of f/5.6 and shutter
Angle of View
speed of 1/60 sec. are set,
adjusting the aperture to f/4 will
This indicates how much coverage
enable a shutter speed of 1/125
of the scene you can see through
sec. to be used. An aperture of
the lens. Telephoto lenses have
f/2.8 will allow a faster shutter
a narrower angle of view than
speed of 1/250 sec. while the same
wide-angle lenses.
exposure level is maintained.
Angle of View and Perspective
Depth of Field
Perspective refers to the distance
Normally, there is only one point of
between the near and far objects
optimum focus. However, we often
that you can see at the same time.
see objects in front of or behind this
When the angle of view is wide
point also in focus. This is made
(with a shorter focal length),
possible by a wide depth of field.
the perspective becomes more
apparent. And with a narrow angle
Depth of Field with the
of view (with a longer focal length),
Aperture and Focal Length
the perspective becomes less
apparent. The image also becomes
The depth of field is mainly
more compressed, with the far
determined by the lens focal length,
objects looking like they are right
aperture and subject distance.
behind the nearer objects.
For example, if a wide-angle lens
is used at the minimum aperture,
Maximum Aperture
almost everything in the picture will
be in focus. However, if a telephoto
This indicates the speed of the
lens is used at maximum aperture,
lens. A fast lens has a large
the background will be really
maximum aperture allowing more
blurred, making the subject in
light to enter. The smaller the
focus stand out.
maximum aperture's f-number,
the larger the aperture opening is.
A larger maximum aperture makes
the image look brighter and easier
to see through the viewfinder.
You can also use a faster shutter
speed or obtain better background
blur. On the other hand, a smaller
Canon EF Lens accessories
General Purpose Filters
Loupe 8x & 4x
for Black-and-White or
Colour Film
Sky (1A), Haze (UV-1), ND (03 • 0.6)
• 52mm • 58mm • 72mm
Conversion Filters for
Colour Film
The Canon Loupe 4x is a high-
80A, 80B, 85, 85B, FCB, FCD
performance magnifier for viewing
• 52mm • 58mm • 72mm
the entire picture area (24 x 36mm)
of a 35mm-format slide or negative.
General Purpose Filters for
With three lens elements in three
Black-and-White Film
groups, chromatic aberration and
Yellow 2, Green 11, Orange 15,
distortion are effectively corrected to
Red 25A
give crystal-clear images. Eye fatigue
• 52mm • 58mm • 72mm
is not a problem even after prolonged
use. Loupe 8x is another magnifier
Softmat Filters
for viewing the entire picture area,
but with special emphasis on a
Softmat filters mildly soften the
24mm-diameter area at the centre.
focus for flattering portraits and
dreamy landscapes. These filters
The four lens elements in four groups
attain high performance and a high
utilise the effect of diffraction which
occurs between light passing through
magnification. All elements have
Super Spectra Coating to make
the transparent part and light
image viewing clear enough for you
passing through the coated part.
Use Softmat No. 1 filter for a gentle
to effectively check the quality of
photos taken with EF lenses. These
soft-focus effect, and Softmat No. 2
two loupes can make your evaluation
for a stronger effect
.
of photos more accurate.
No.1, No.2
• 52mm • 58mm
Drop-in Filters
Warming Filters for
Drop-in Filters PL-C
Colour Film
Drop-in Filters PL-C
can be rotated from
81A, 81B
the outside without
• 52mm • 58mm • 72mm
removing them from the lens for
precise control. The 48mm
Circular Polarising Filters PL-C
PL-C filter can be used with the
Polarising filter enhances picture
following lenses – EF 200mm
quality by blocking harmful reflected
f/1.8L USM and EF 1200mm
light. Use it to reduce polarised
f/5.6L USM; the 52mm PL-C filter
light reflections from glass and
is designed for use with the
water surfaces or to improve colour
EF 300mm f/2.8L IS USM,
saturation. Simple to use, circular
EF 400mm f/2.8L IS USM,
polarising filters (such as Canon's
EF 500mm f/4L IS USM and EF
PL-C) polarise light circularly, rather
600mm f/4L IS USM.
than linearly, so it does not interfere
Drop-in Gelatin
with autofocus or TTL light metering.
Filter Holders
• 52mm • 58mm • 67mm • 72mm
These glass-backed
• 77mm (Type II)
holders accept up
to three commercially available
cut-to-size gelatin filters for
rear-insertion lenses. A 48mm
holder is provided standard with
EF 200mm f/1.8L USM and EF
1200mm f/5.6L USM; and a
52mm holder, with
EF 300mm f/2.8L IS USM,
EF 400mm f/2.8L IS USM,
EF 500mm f/4L IS USM and EF
600mm f/4L IS USM.
Drop-in Screw
Filter Holders With
Protect Filters
The enclosed regular
filter can be exchanged with other
commercially available screw-type
filters. Note that only filters with
correct filter frame thickness can
be mounted on the lens.
• 48mm • 52mm
Only Canon Filters are guaranteed for use
with EF lenses.
Gelatin filter Holders III & IV
Gelatin Filter
Gelatin Filter
Holder III
Holder IV
Gelatin Filter Holder III uses 3 x 3
inch gelatin filters and Gelatin
Filter Holder IV uses 4 x 4 inch
gelatin filters. Holders III and IV
both provide extension hoods
and 52mm, 58mm, 67mm, 72mm
and 77mm adapters. Refer to the
EF Lens Accessory Table for
information on lens combinations.
• 52mm • 58mm • 67mm
• 72mm • 77mm
• Adapter III for EF 50mm 1: 1.4
22
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