Classic SLRs Series :
T-90 - Its Metering Capabilities
File Size: HTML (23k) Loading....
area SPC for center weighted average metering and also handles the partial metering
for spot and A-TTL/TTL metering.
views of the
SPC that handle the TTL flash at the mirror box.
One of the key selling points for any camera is its metering capability. Whether
we like it ornot, everyone uses the camera's built-in metering as a reference point
prior to clicking the required scene. And metering technologies have advanced to
such a state that Evaluative and Multi-pattern metering can even take into considerations
the subject's distance and color temperatures of the scenes (Nikon triumphed in this
area, with its F5 model). In 1983, Olympus launched its twin flagship
model OM3 & OM4 that incorporated multi-spot metering to replace its OM1 &
Canon was ambitious to make use of the T90 as the ultimate metering machine, packing
all known metering patterns that were available by its competitions - EXCEPT Nikon's
multi-segment metering that was first seen on the Nikon FA of 1983. To begin with,
the Canon New F-1 has three metering options which were upgraded for the T90 by making
it unnecessary to physically change the focusing screens like the New F-1 to achieve
the desired pattern of Center-weighted, Partial and Spot. These metering can be changed
with a couple of pushbutton controls plus a twist of the Electronic Input Dial. The
Olympus's way of Multi Spots Metering and Highlight/Shadow Control was "borrowed"
but enhanced further and all these various functions can be use in combination with
the AE (Auto Exposure) lock.
A more detailed descriptions on these are available next page.
Metering works best in some selective situation since it measures 13% within the
picture area for more precise control of un favorable lighting condition.
conventional center weighted average metering is provided for general photography.
Giving preferences more to the center area and this can work with AE lock, exposure
Spot metering: concentrate at the 2.7% of the picture area. Giving extreme precise
light measurement. Can work in conjunction with another feature, the H/L Control.
||On top of
these three metering patterns, the T90 provided the users with an even more precise
metering method, the Multi-spot metering capability. See next section.
USE the MAIN MAP 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.
These three major
features in metering can work along with supplementary features like: its Exposure
Compensation, AE Lock and H/L Control.
The T90 features two sensor elements, one of which is a double area SPC like the
one used in the Canon T70. This element is set at the upper part of the eyepiece.
The other element is located at the bottom of the mirror box. The double area SPC
is a sensor element used for center-weighted average metering and partial metering.
Spot metering is handled by the second sensor element. Both sensor elements are controlled
by the micro-circuitry which makes up the brains of the metering system. For example,
IC is used for spot metering and another for TTL automatic control.
Spot metering can be used in three ways: One point spot metering, multi-spot metering,
and H/S Control. When the Spot Metering Button is pressed, exposure values are stored
in the camera.
metering sensor located at the base of the mirror box has 3 functions: Providing
ordinary spot metering, pre-exposure spot metering at FEL when using the 300TL dedicated
flash, and real-time metering with the A-TTL/TTL automatic dimmer modes. This innovative
sensor is directed by the sub CPU through an I/O device.
* The A-TTL metering is a clear departure from the New F-1n way of handling its flash
metering - the Canon
F-1 has a automatic CAT system
while the Canon F-1 developed from there and among the top professional models available
during the early and mid-eighties, Canon is the only camera manufacturer that is
still resisting of incorporating TTL flash meter under the main reflex mirror. (We
will discuss that part of WHY Canon opposing to main stream technology when the New
Canon F-1n site is up).
section will detail all the above metering capabilities and various control on the
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.
to Main Index Page
A & T series SLR Models
FL | Canon FDn lenses. | Early versions of FD lenses
| Message Board |
for your Canon T90
| Message Board | for your Canon optics
in a shared environment
| Message Board |
Dispose for Looking or Canon Photographic
Home - Photography
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.