Classic SLRs Series :
T-90 - Exposure Control
Shutter Priority AE /Stopped Down Metering
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Many have mistaken the Canon
AE-1 of 1976 as the first Canon to employ Shutter-priority automation. Well, prior
to that, the Canon EF in 1973 already has a shutter speed-priority TTL automatic
exposure incorporated within. Its hybrid copal square shutter control speeds from
1/2 sec. to 1/1000 sec and bulb mechanically while slower speeds from 1 sec. to 30 sec. were electronically-controlled.
The AE-1 was a true Shutter-priority AE camera. Anyway, no one doubts that Canon
has the leading edge in the development of Shutter-priority automation - for a brief
spell, Minolta did surprise many with its debut of the XD-7, which was the first
ever multimode SLR, and Canon relied handsomely with its highly successful Canon
A-1to counter any threat from that model during the late '70s. Well, just for the
information, the first Nikon permitting Shutter-priority AE was the Nikon FA in 1983
after they have upgraded the Nikkor lenses to the AI-S series.
Although most of the manufacturers preferred Aperture-priority AE than Shutter-priority
AE, which doesn't involve the physical change of the communication of data input
between the lens and camera body, Canon's persistent was seen as quite 'odd' - but
AE mode found its core supporter with sports photographers and other professionals.
With the T90 operating in the Shutter-priority AE mode, you can capture all the action
by selecting the appropriate shutter speed. You dial in your choice via the same
convenient Electronic Input Dial, selecting from 35 different speeds–ranging from
1/4000 sec. 30 sec. in half-step increments for the ultimate in precision. Once the
shutter speed is set, the T90 automatically selects the correct aperture.
Well, the "which
mode is better" debate has been going on for the last 2 decades. Both have their
strengths and weaknesses as the preferred automation in camera operation. Being two
of the main features of any modern 35mm SLR camera, the factors are interlocking.
Basically, both the shutter speed and aperture values alter effects. We have briefly
on the aperture earlier of the eventual effects
it might yields with varying values. With a shutter speed control, say, in order
to capture a sense of motion - lower speeds are best suited to achieve such effect.
On the other hand, the use of fast shutter speeds for photographing a fast action
event like racing cars can have an opposite effect, making them appear to be frozen.
Well, it is possible to achieve an almost unlimited range of photographic effects
just by being aware of what happens when you use different aperture settings and
Half step shutter speeds ? No problem.
Note the "Tv" setting appeared at shutter priority automation.
Refer to the
T90 for cross reference.
to set the mode ? While pressing the Shooting Mode Selector, turn the Electronic
Input Dial until the Shutter-priority AE mode symbol (Tv) (Time value) appears on
the Display Panel. Release the Shooting Mode Selector and continue to turn the Electronic
Input Dial until the shutter speed you want appears. The correct aperture is shown
inside the viewfinder, so you can check the shutter/aperture setting without looking
up from the lens you are photographing.
dial is an integral part of the whole system for command.As most of the required
tasks or changes can be handled by the Electronic Input Dial. It lets you to easily
and quickly choose from among a total of 35 different shutter speeds.
No matter how quickly the pace of the activity you are shooting changes, you can
dial in a new shutter speed to match it. This unique feature of the T90 is sure to
improve your high-speed shooting technique. And it is particularly useful when you
need to work with the fastest possible shutter speed in dim lighting.
button can be activate to monitor out of exposure range and put you back in command.
There is a safety control feature for the unexpected. The T90's Safety Shift can
be switched on to automatically override the set shutter speed in order to avoid
over or underexposure.
If the selected shutter speed is too slow or too fast for existing light conditions,
the T90 automatically switches the shutter speed to the correct setting. To set the
Safety Shift mechanism, you simply press both the Film Speed Button and the Exposure
Compensation Button at the same time for approximately 1 sec. The "SS"
mark will appear on the Display Panel, indicating that Safety Shift will be activated
special creative effects or intentional over- or underexposures, pressing the same
two buttons disengages the Safety Shift function.
Blur for portraying movement or action freezing ? The possibilities can be endless.
The T90 can free you to experiment with your creative sense or preference.
for the viewfinder
and LCD display
for cross reference in this site. Another page is also equally helpful for its layout of
controls and buttons.
Have we forgot
about the basic manual setting ? Well, if all of these advanced automation are not
your cup of tea (Why buy it then?), the T90 has the Stopped Down (Fixed Index) Metering
for you to toy around. It allows complete manual operation.
Even when you are in this mode, you can still check for correct exposure by simply
selecting the shutter speed using the T90's Tv mode and then adjust the f-stops from
the aperture ring, after disengaging it from the 'A' mark. The viewfinder display
indicates correct exposure, over and under exposures and "help" will appear
to instruct you to close or open the aperture.
The stopped-down AE mode is used when
shooting with non-FD lenses like the Canon FL lenses or with FD lenses mounted to
close-up accessories such as FL-type of extension tubes or bellows, both of which
have no signal pins.
By selecting the T90's aperture
priority AE, standard Program AE, or variable-shift program AE, you can directly
choose the aperture setting using the aperture ring on the lens then push the stop
down lever and the T90 automatically determines the correct shutter speed. Thus,
by this method, you can still enjoy AE performance even with a 7.5mm fisheye lens,
Reflex lens or TS lens.
The Canon TS (Tilt and Shift) lens has no Automatic Aperture Lever and you can use
this mode to perform metering this way).
* Refer to the LCD main map of T90 for cross reference.
Macro photography presents
particular problems in controlling depth of field because of the very short focusing
distances. When using a bellows or extension tube between the camera and lens, the
stopped down AE mode is essential because there are no FD-type of signal pins to
interlock to the "A" mark.
If during the Stopped Down mode, you accidentally set the lens to "A" mark,
the error message will appear. Click here for an illustration. With the T90 in the stopped down
AE mode, you can control the effects you want since you can visually observe depth
of field while selecting the aperture values. Stopped down AE makes even "Pinhole"
photography easy since the T90 is so sophisticated, it can take even a "pinhole"
photograph using AE operation.
You can use the Stop Down
Lever to visually confirm the depth of field when shooting in the stopped down AE
mode, the most commonly used method when using lenses without FD signal pins.
Concept | Capabilities
Metering, Exposure control, Flash photography, Viewfinder display, Film Backs, Built-in Motor Drive, the brains, Focusing Screens Other capabilities and the eyes
Full specifications with details illustrations of its various controls, available
in HTML / PDF (184K) format.
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leofoo ®. MIR Web Development Team.
Maintenance Team: Credit: Pawel Nabe for his image
on the Data Memory Back. EEwyn Foo, my nephew,
who has spent quite a number of nights converting the original manual in HTML format.
Mr. Richard Yeow, General Manager
-Optical Division of Canon Marketing for granting special
permission to reproduce this manual into HTML format in his site as a form of obligation
to all the T90 users worldwide. Maintainders of the T90 Message Board: Kaipin, Terry Carraway & Dr Strangelove; Tom Scott, for his images
of the SPD cell, Chris Tutti for his initial effort
to scan and prepared the T90 manual in PDF format. My staffs Miss Wati and Mirza for helping the basic setup
work. * Canon, T90, FD Lenses, Canon Marketing are registered trade
names or trademarks of Canon Inc. Japan.