26
Built to Perform: Durable,
Rugged, Precise
1-Series Body
EOS-1Ds Mark III retains and refines the beau-
tiful curved surfaces and superb basic layout
of the EOS-1 series. Ease of operation and
holding comfort have been improved appre-
ciably, as has ease of operation with acces-
sories. The camera is designed to be easier to
understand and more reassuring. The massive
strength of its magnesium alloy body and
chassis, combined with complete environ-
mental sealing, means that the camera
stands with its forebears as an instrument
worthy of the photographers who risk their
lives daily to take pictures.
All-magnesium Alloy, Including Mirror
Box and Chassis
Because of its light weight and strength, mag-
nesium alloy is used for the top, front and
rear covers as well as for the memory card slot
covers. The chassis and mirror box are also
made of magnesium alloy to make the body
very strong, rigid and light. The magnesium
alloy also works as an electromagnetic shield.
It is highly durable, allowing minimal wear
even under harsh conditions.
Shutter
Durability, Tested
to 300,000 Cycles
The EOS-1Ds Mark III’s
shutter unit is rated
for 300,000 shutter
cycles. To attain this
level of ruggedness, surface finish and heating
processes in manufacturing have been changed
for specific highly durable parts. To increase
stability and shutter precision, a PR (Photo
Reflector) is employed to detect the slit-passing
time. For the X-sync contact, the mechanical
contact has been eliminated to prevent contact
scorching and wear.
By employing PR signals for the electronic X-sync
contact (a semiconductor switch), reliability is
improved. By optimizing the sync timing, an
X-sync speed of 1/300 second is now attained
with EX-series Speedlites.
63-zone Metering System
The EOS-1Ds Mark III incorporates a 63-zone
metering sensor linked to the 19 AF points.
The metering sensor is located at the rear of
the pentaprism. The 19 AF points in the Area
AF are a highly favorable match for the meter-
ing sensor’s zones. The metering range is EV
0 to EV 20 (at 73°F/23°C, 50mm f/1.4 lens,
ISO 100). The following metering modes
are provided: Evaluative, Partial, Spot, and
Center-Weighted average. Also, AF p oint-linked
Spot metering is possible with C.Fn I -7-1.
Partial metering reads approximately 8.5% of
the viewfinder and Spot metering reads
approximately 2.4%.
This Evaluative metering system is based
on the concept for the previous 21-zone and
35-zone metering systems. With the optimized
63-zone metering sensor and improved calcu-
lations and processing, more consistent and
correct ambient and flash exposures are
obtained with less influence from the subject.
The basic concepts for the 63-zone Evaluative
metering are:
1. Metering is weighted on the linked AF point.
2. If there is a very bright object in the picture,
the exposure will be increased.
3. In backlit scenes, the exposure will be
increased. With dark backgrounds, the
exposure will be reduced.
The E-TTL II autoflash algorithm uses the
same 63-zone metering sensor. While based on
the previous system which weighted the meter-
ing based on the preflash reading, the EOS-1Ds
Mark III has been improved to obtain consistent
flash exposures. The major improvements are:
1. Correct flash exposures are obtained even
with off-center subjects.
2. The incorporation of lens distance informa-
tion has been optimized to obtain accurate
flash exposures even with highly reflective
backgrounds.
EOS-1Ds Mark III Magnesium-alloy Body
25
Speed and Predictive-AF Performance
The EOS-1Ds Mark III features higher precision
AF with the 19 user-selectable, high-precision
cross-type AF points and improved low light AF
performance. The AF sensor, AF computation
method and AF-related electronic circuitry has
been designed for the EOS-1Ds Mark III. This
robust AF system provides even greater consis-
tency in high-speed sequences when tracking
moving subjects.
Separate CPU for AF
One important difference between the EOS-1D
series and other EOS series bodies is that a
totally separate CPU is used strictly for AF
processing. (In other EOS bodies, one main
processor handles primary camera tasks as
well as AF processing.) To attain 10 fps with
AI Servo AF (EOS-1D Mark III), the AF CPU
and camera CPU are separate, dedicated
processors.
The 19 cross-type AF points take advantage
of the following technologies:
• With finer processing steps, the peripheral
circuit could be made smaller and the f/2.8
AF sensor area could be expanded.
• The secondary image-forming lens (see
diagram) is molded glass. By incorporating
an aspherical surface on the lens, the
focusing area of the f/2.8 light flux could
be expanded.
Each of the 19 cross-type AF points uses a
high-precision horizontal component, with
about 3x the focusing precision of the vertical
component. The benefit is that AF accuracy at
the sensor is enhanced when the photogra-
pher needs it most — shooting with fast lens-
es, at wide apertures.
This means that on the actual AF sensor,
the horizontal line pairs are significantly farther
apart — and thus require a lens with a
maxi7mum aperture of f/2.8 or faster in order
to operate. At the center AF point, the high-
precision horizontal line sensor works with
lenses f/4 or faster. In other words, with
fast lenses, two benefits are realized:
added precision, and simultaneous vertical
and horizontal coverage — ideal for focusing
on subjects with fine detail. When lenses
with slower maximum apertures are used,
only the vertical AF line sensor is active at
each AF point.
Advanced technology in the EOS-1Ds
Mark III’s AF sensor gives even greater light-
gathering efficiency (for both the horizontal and
vertical line sensors), and greater low light AF
sensitivity. In addition, the camera’s ability to
latch onto subjects with little detail is improved.
Lenses (or lens + extender combinations)
with maximum apertures as slow as f/5.6 can
be used with AF at all focusing points. At the
center AF point only, the camera can focus with
a lens + extender with a maximum effective
aperture as slow as f/8 (using the vertical line
sensor only).
The remaining 26 AF points are “Assist
Points.” Each has a single-line vertical sensor,
and these points will focus with lenses having
maximum apertures f/5.6 or faster.
With the EOS-1Ds Mark III, the size of a
user-selected AF point can be expanded
(via Custom Function III-8) regardless of
whether the camera is in One-Shot AF mode
or AI Servo AF mode. As noted previously,
the assist AF points are also used when the
camera picks the AF point(s) in Automatic AF
point selection mode.
For low-light focusing, the EOS-1Ds Mark III
is much more sensitive than previous models.
The CMOS AF sensor’s pixel sensitivity has
been improved, thanks to pixel characteristics,
a pixel fill factor due to fine semiconductor
manufacturing processes and optimized pixel
size. As a result, the EOS-1Ds Mark III’s AF
sensitivity have been improved to EV -1
through EV 18 (at 73°F/23°C, ISO 100).
Prime lens
Subject
Focusing plane
(Image plane)
Secondary
image-forming lens
CMOS area sensor
AF Focusing Principle
TECHNOLOGY
Actual AF Point Field-of-View
6.6
7.50
4.5
3.00
2.25
4.00
2.0
0
(C
AF Sensor configuration
* C.Fn I -7-1 enables AF point-linked Spot metering.
Evaluative/Center-Weighted
average metering
Partial metering
Spot metering
Shutter Unit
Shutter Design Specifications
Item
Specification
1. Type
Vertical travel, focal-plane shutter
2. Shutter curtain type
Parallelogram link type
3. Shutter curtain blades
1st curtain: 4 blades,
2nd curtain: 4 blades, total 8
1st curtain: Two carbon blades,
two duralumin blades
2nd curtain: Two carbon blades,
two duralumin blades
4. Shutter curtain
materials
5. Drive system
1st curtain: Dedicated torsion spring
2nd curtain: Dedicated torsion spring
6. Speed control method
Mechanical shutter with tension released
by a rotary magnet, all shutter speeds
electronically-controlled
7. Curtain speed
Approx. 2.3ms/21.0mm
8. Shutter speed range
1/8000 sec. – 30 sec. bulb
9. Max. flash sync.
1/300 sec.
10. Signals
1. X-sync,
2. 2nd curtain travel-completed signal
Sync
contacts
PC
terminal
Shutter PR
MPU
Non-Canon
flash
External
Speedlite
Semiconductor
switch
(Electronic
X-sync contact)
Semiconductor
switch
(Electronic
X-sync contact)
Electronic X-sync Contact Diagram
Sensor horizontal-line
sensitive at f/5.6
Sensor vertical-line
sensitive at f/2.8
Sensor vertical-line
sensitive at f/2.8
Sensor horizontal-line
sensitive at f/5.6
AF Sensor
(C
: f/2.8 sensors
(Cencer AF point is f/4)
: f/5.6 sensors
