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Canon
EOS 10D Review • AF &
Metering
Peter
Kun Frary
Auto
Focus
The EOS 10D's auto
focus design is a balance of flexibility,
speed and accuracy. Like the EOS 1V, 3, and Elan 7,
the 10D uses a CMOS chip for its AF sensor, as opposed
to the BASIS or Multi-BASIS chip used in older EOS
cameras such as the A2 or 1N. The seven AF sensors are
arranged in a cross array similar to the Elan 7 and
Rebel Ti:
The center AF sensor
is a cross sensor and is sensitive to horizontal,
vertical and diagonal lines. The top and bottom
sensors are horizontal sensors and are sensitive to
vertical and diagonal lines. The remaining AF sensors
are vertical sensors and are sensitive to horizontal
and diagonal lines. Seven cross sensors would be
ideal, but this design yields a good balance between
horizontal and vertical sensitivity. The seven AF
sensors cover a larger proportion of the frame than
those in the Elan 7 or Rebel Ti. Moreover, the sensors
cover nearly twice as much area as indicated by the
focusing rectangles. Here's
a diagram illustrating AF sensor
coverage.
Ala Moana
Boulevard
After Sunset
• EOS 10D & EF 70-200 4L USM • P
mode
Individual sensors may
be selected manually with the main input and QCD or
automatically via fuzzy logic. The advantage of this
system is that you can focus off-center subjects
without locking focus and recomposing. AF modes
include One Shot (stationary subjects), AI Servo
(predictive follow focusing of moving objects) and AI
Focus (automatic selection of One Shot or AI Servo).
To select a sensor is a two step process:
1) Press AF
point selection button.
2) Turn main input
dial for vertical sensors or QCD for horizontal
sensors.
Custom function 13-3
may be invoked for direct use of the QCD without use
of the AF point selector. Custom function 13-1 allows
the assist key to instantly select your favorite AF
sensor. AF sensor selection options on the Elan 7E are
faster, more flexible and convenient, especially the
dedicated buttons on the QCD and ECF.
Manual AF point
selection functions in the Creative Zone and is not
operational in the Basic Zone.
AF
Sensitivity
In good light, AF is
fast, about the same speed as the Elan 7E. As light
gets dimmer, the Elan 7E's performance begins to waver
and the EOS 10D pulls ahead. Canon
specs autofocus of the Elan 7E at EV 1-18 with an EF
50 1.4 USM lens. The EOS 10D is only a half stop more
sensitive at Ev 0.5-18. However, performance at Ev 5
or 6--where the Elan 7 begins to have problems--is
definitely better. Even with a slow zoom, e.g., EF
24-85 3.5-4.5 USM, I found low light AF acceptable,
although not as good as my EOS 3.
How To Improve Low
Light AF
All autofocus SLR
cameras share similar limitations when shooting in low
light. In low light photography, it is crucial to use
fast lenses and focus on points of contrast. In other
words, you can't merely point 'n shoot when lighting
gets dim. You must pick your targets carefully. Here
are some tips for low-light photography with the EOS
10D (these tips are useful with any EOS
camera):
When it is really dim
(e.g., a living room lit by table lamps), it is best
to use only the center cross sensor (at this point
you'll need a tripod). That is, manually select the
center sensor and turn off all other AF sensors. It is
extremely important to lock focus on a contrasty
detail, e.g., an eyebrow rather than a smooth
forehead. Furthermore, low light AF is enhanced
considerably by using a fast prime lens such as the EF
50 1.4 USM or EF 35 2.0, rather than a slow zoom. The
increased depth of field of a wide angle lens, e.g.,
EF 28 2.8, also helps improve low light AF. A bright
image in the viewfinder is an additional benefit of
using a fast lens.
In candlelight
murkiness or complete darkness, you must use the
irritating "AF assist light" (pop up flash) or the AF
assist light of a Speedlite to autofocus. With a
near-infrared AF assist light you may use automatic
focusing point selection. It's a shame Canon omitted
the built-in near-infrared AF assist light. It made
low-light AF elegant and convenient on older bodies
such as the A2 and Elan II. When discreetness is
paramount, you may disable the flash with a custom
function (CF5-3) and use the AF assist light of
Speedlite only. If you have good eyesight, you can
still focus the old fashion way, manually!
AI
Servo
This is a great camera
for amateur sport shooters. Lock on to a moving
subject in AI Servo, keep the shutter pressed halfway,
and the camera tracks the subject as it moves from
side to side (sensor to sensor) and towards or away
from you. It confirms side to side movement with red
sensor flashes! Very cool. AI Servo seems a little
better at nailing sharp images than the Elan
7.
AF Problems: Too
Many Choices?
With all these AF
choices, how can you go wrong? Actually, you can by
choosing an inappropriate operation mode for your
subject or shooting style. Tyros frequently complain
the EOS 10D produces blurry images. They use Full Auto
and let the fuzzy logic chip select the subject.
Unfortunately, it may lock AF on a shinny foreground
object or a bright background rather than the intended
subject.
The cure is to take
control of the camera, rather than letting it control
you. When auto AF point selection fails, use manual AF
selection, lock-AF-recompose or manual focus. With
experience, you'll learn to engage the best technique
for each situation.
Exposure
Controls
Like the A2, Elan and
Rebel series, the EOS 10D's exposure modes are divided
into two groups, the Basic Zone and Creative
Zone. The Basic Zone consists of programmed point
'n shoot modes: Full Auto, Portrait, Landscape,
Close-up, Sports and Night Scene. The Creative Zone
sports semiautomatic and manual modes: Program AE,
Aperture Priority, Shutter Priority, Manual and
Automatic Depth of Field. These modes are clearly
labeled and available at the twist of the Mode
(Command Dial in older EOS jargon), a big knob on the
top left side of the camera. Incidentally, the Mode
Dial feels solid but is a little looser than the Elan
7. There is no lock button.
Creative Zone modes
may be customized with special drive, AF and flash
settings; custom functions; -2 to +2 of exposure
compensation via the QCD (big wheel on the back) and
auto bracketing. These settings don't function in the
Basic Zone as Canon is afraid beginners might ruin
pictures by accidentally touching camera
controls.
Full Auto
Mode
Full Auto and Program
AE (P) are intended for general snapshots and follow
similar algorithms. However, Program AE is a Creative
Zone mode and, therefore, allows user customization
and manual overrides. In contrast, Full Auto is a
point 'n shoot mode and thus allows no manual
overrides or customization. Fuzzy logic is used to
control exposure, AF and flash. If the camera detects
motion away or towards you, it switches to AI Servo
(follow focus). If light is dim, the flash pops up.
These modes are useful when you're in a hurry or you
hand the camera to someone to take your picture.
Unfortunately, sometimes the camera chooses silly
aperture/shutter combinations. For example, with an EF
50 1.4 USM mounted and my camera pointed out the
window, Program AE indicates F3.5 at 1/500 sec. This
is a sensible exposure with an EF 300 2.8L USM.
However, F4.5 at 1/250 or F6.7 at 1/25 are better
choices with a 50 mm lens. Although you may shift the
program, I find Aperture Priority (Av) a better mode
for most of my photography.
Programmed Image
Modes
Portrait, Landscape,
Close-up, Sports and Night Scene are specialized
variations on Full Auto and are targeted at tyros. For
example, Landscape mode is supposed to be used with a
wide angle lens for sweeping vistas. To enhance depth
of field, the camera stops down a little more than
Full Auto, but not enough for my taste. Aperture
Priority or A-DEP mode afford much better control of
depth of field. The Programmed Image modes perform as
advertised but may be improved on by user control in
the Creative Zone. I don't use Programmed Image modes
and would be happy if they were omitted from the
design. Canon could use the savings to add a proper AF
assist light!
A-DEP
Mode
DEP has been one of my
favorite modes since I bought an EOS 10S in 1990. DEP
mode automatically sets optimal F-stop and hyperfocal
settings for maximum depth of field. Back in the day,
we stopped down and used the depth of field (DOF)
scale to manually set hyperfocal distance. Of course,
back in the day most lenses were primes and had
distance and DOF scales. Today, many zooms lack both
distance and DOF scales and, subsequently, there isn't
a practical way to maximize DOF. That is, until Canon
invented DEP mode.
Unfortunately, the EOS
10D sports A-DEP mode, not DEP mode. What's the
difference between A-DEP and DEP? A-DEP requires
simultaneous alignment of AF sensors on the nearest
and farthest objects desired in focus--a near
impossible task! DEP lets you focus on the nearest and
farthest objects separately. There's one more step but
it always works.
Diamond Head View
• EOS 10D & EF 24-85 3.5-4.5 USM. This
image is one of the rare times I achieved simultaneous
alignment of AF sensors on the nearest and farthest
objects desired in focus! Usually the fuzzy logic
algorithms gave me a fuzzy image! A-DEP is nearly
useless.
Meter Patterns
& Metering
Like the Elan and
Rebel series, the EOS 10D has three metering patterns:
evaluative, center-weighted and partial. Again, like
the Elan 7E, the 10D uses a 35-zone silicon photocell
(SPC) for metering. These zones are evaluated by the
camera's CPU and supposedly render better exposures
than earlier 6, 16 and 21 zone SPCs. However, in
practice this is not true. For example, I found my
21-zone EOS 3 more accurate in difficult situations
than both the Elan 7E and EOS 10D.
The EOS 10D has a 9%
partial metering pattern (center circle). The original
Elan is 6.5%, the Elan II 9.5% and the Elan 7E 10%.
Smaller patterns are more desirable as you can
precisely measure isolated areas of the picture (a
true spotmeter of 2 to 3% would be even better). Of
course, a large partial pattern is easier for tyros to
use. Unlike the Elan 7, partial metering can't be
linked to the active AF point.
Exposure
Accuracy
I mainly shoot chromes
with my EOS film cameras and am accustomed to exacting
exposure requirements and narrow latitude. The EOS 3,
Elan 7E or A2 nail exposure about 90% of the time in
Evaluative metering mode. The remainder of the time I
use spot metering, exposure compensation or substitute
metering techniques to arrive at a desired exposure.
The 21-zone metering of the EOS 3 is especially good
at handling difficult lighting situations. In
contrast, the 10D needs -1/3 to -1/2 exposure
compensation during sunny days to keep highlights from
blowing out! What's the deal here?
The EOS 10D's meter is
dead on according to the "sunny F16 rule." That is,
with ISO 100, a meter reading off a Kodak gray card
indicates 1/90 at F16 in the midday Hawaiian sun
(shutter speeds are stepless but 1/90 is the nearest
readout to 1/100). With Custom Function 6.1 set (1/3
stop increments), 1/100 at F16 is indicated. So why is
exposure compensation needed if the meter is dead on?
The answer to this riddle is that digital sensors have
narrow exposure latitude and, thus, can't record the
extremes of shadows and highlights present on a sunny
day.
Specifically, the
10D's CMOS sensor has a recording range of about 5
stops, similar to slide film and half that of print
film. Unfortunately, the CMOS image sensor has even
less tolerance of overexposure than slide film. Thus,
highlights blow out or clip with slight overexposure.
On the other hand, Photoshop can pull shadow detail
out of 10D files that couldn't exist in slide film.
Canon needs to tweak the Evaluative algorithms to
recognize a sunny day and to compensate to keep
highlights within the 5 stop range of the imaging
sensor. At any rate, it's better to error slightly on
the side of underexposure for the sake of highlight
detail. In dimmer light exposure is usually dead on
and exposure compensation isn't needed.
All meters can be
fooled and you must learn when to override them (e.g.,
bright sunsets, strong backlight, predominantly light
or dark scenes). However, I have to override the 10D's
meter more than any camera I have owned! If you're
able to think and meter selectively, center-weighted
and partial metering yield more consistent results
than Evaluative. The key is to meter for important
highlights--i.e., place them on the extreme right of
the histogram--and let the shadows go
black.
Exposure Meter
Range
The EOS 10D has meter
range of EV 1-20, same as the Elan 7. The 1991 Elan
had a metering range of EV -1 to 20. I want the 2
extra stops of meter sensitivity back!
Digital
Work Flow
One of the main differences
between DSLR and point 'n shoot
digicams is digicam images are highly processed in-camera.
That is, they have large amounts of sharpening, saturation
and contrast automatically added to the image upon
cature. Thus, digicam
images are optimized from the getgo to look good on computer
monitors. DSLRs have little or no processing added
to the image. Even if you adjust parameters to maximum settings,
you still can't duplicate the
heavily processed look of digicams. Why are DSLRs designed
this way? To simulate the photographic look of film--rather
than a processed digital look--and allow the user to apply
creative options according to taste and need.
DSLR images are designed primarily
for printing and that's where they really show their stuff.
Think of EOS 5D files as digital
negatives. Negatives need interpretation--adjustment--to look
their best. Here's my basic workflow:
1. I upload RAW images
to computer via card reader and open thumbnails in EOS Viewer
Utility (EVU) or Digital Photo Professional (DPP).
2. If needed, I adjust parameters
(WB, exposure compensation, etc.) and/or Pictures Styles
to taste.
3. After parameter adjustments,
I convert to a lossless format such as 16-bit TIFF. This
file will serve as my master work file.
4. If needed, Photoshop adjustments
are performed and
saved.
4. Finally, I resize and sharpen
multiple versions for specific print sizes or web display
(I use "Save As" for optimized JPEG versions).
Never save a master work file
as a JPEG. Always use TIFF or native Photoshop image format.
If tweaks are needed in the future (levels, resizing, sharpening,
etc.), you can adjust the master work file in Photoshop without
loss of image quality. If you screw up the work master, you
can always go back and convert the RAW file again to 16-bit
TIFF (hopefully you stored it in a safe place!).
Fortunately, 10D files normally
need less tweaking than scans from my Canon
FS4000US film scanner.
Moreover, 10D files are robust: they can tolerate more sharpening
and enlargement than film scans. However, uploading, browsing
and converting is time consuming--more so than using a light
table. It takes all dad burn day. With digital you do all
the lab work! With film you pay the lab to do most of it...
Why do I shoot RAW most of the
time instead of JPEG? It yields ultimate quality images with
maximum control and creative options. Raw image characteristics
may be altered in the EOS Viewer Utility (EVU) or Digital
Photo Professional (DPP) without degrading data. Plus, most
of the parameters in EVU or DPP are the same parameters available
in camera: exposure compensation, white balance, sharpness,
contrast, color tone, saturation, color space and display
size. EVU or DPP allow you to apply parameter changes as if
set when the picture was taken.
Both Canon's conversion applications
get the job done extremely well, albeit the thumbs load rather
slow. The resulting TIFF file requires fewer post-conversion
tweaks than Photoshop CS or Phase
One Capture One DSLR.
I prefer DPP over EVU due to the better interface, display
and batch processing. However, conversions are equally good
in both programs. If you work with RAW files regularly, you'll
crave a fast computer.
There are other RAW converters
available if you're willing to pay. The poor man's Photoshop, Graphic
Converter ($30 shareware),
can convert RAW files but lacks parameter controls (you're
stuck with defaults). However, it makes a fine companion to
Canon's software due to its batch processing, slide show,
image adjustment tools, browser and ability to open over 150
image formats. Of course, Photoshop CS ships with an excellent
RAW conversion plug-in and is a must-have for any 10D owner. Phase
One Capture One DSLR is
reputed to be the best RAW converter but, at $500, it better
be.
©Copyright
2003-2006 by Peter Kun Frary • All Rights
Reserved