Modern Classic SLRs Series :
Canon T-90 - Exposure Control
Aperture Priority & Program Automation Exposure control

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Aperture-priority AE allows the photographer to control the depth of field. A wider aperture results in shallow depth of field, centering attention on the main subject. Narrowing the aperture setting gives more depth of field so that objects of both near to and far from the main subject are in sharp focus. Once you dial in the aperture using the Electronic Input Dial, the T90 automatically selects the correct shutter speed. Conventional style requires a user to turn the aperture ring and preset the f-stop aperture and using an viewing aid like Depth of Field Preview button to preview the desired result, and some just use the depth of field setting engraved on the aperture ring of the lens as the guideline.

Generally, the wider the aperture setting (bigger numbers like f2.8, f2.0, f1.4, etc.) ensures that the subject alone will be in focus and is the center of interest while the rest of the surrounding areas will be blur and out of focus, creating a strong and powerful impact isolating effect, a style which very important in portrait photography. On the other hand, a small aperture setting (smaller numbers e.g. f16, f22, etc.), is chosen, making both the foreground and distant background sharply in focus. This approach is best used for landscapes.
To get the most out of a lens, the aperture control is equally important. Different characteristics are displayed when lenses are stopped down or opened up. Depth of field varies both with aperture setting and the lens' focal length. So a stopped down wide-angle lens will have almost everything in focus, while a telephoto lens set at a large f stop gives out blurred backgrounds and keeping the main subject in sharp focus.

The T90's Aperture-priority AE mode lets you select exactly how much depth of field you want in your photograph, giving you full creative control over the final image.

Moreover, the Aperture-priority AE supports the switchable Safety Shift function in the same way as it does with the Shutter-priority AE mode.


Safety Shift : With the T90 set on shutter-priority AE or aperture priority AE, press with the Film Speed Button and the Exposure Compensation Button for about 1 sec. The "SS" mark indicates Safety Shift will then appear on Display Panel. The same operation clear the Safety Shift function.

Aperture Control and Lens Selection of the depth-of-field varies depending on the focal length of the lens you are using. More dramatic differences in depth of field control can be achieved by using telephoto or wide angle lenses. With the automatic nature of the aperture priority AE mode, no matter what the focal length of the Canon FD lens you may have select, you will have total control over the depth of field in your photograph (The Canon has a very interesting point and click way of selecting the depth of field control in the later models). You can choose from among a wide range of values (a total of 36 settings in half stop increments) to bring out the full visual characteristics of your photograph.

Although since the early days of automation, from the more well known AE-1, aperture priority automation was not Canon's preferred way of exposure control, even though its early batch of FD-type lenses do have information being remitted to the camera body. The first popular Canon model that offered only the Aperture-priority AE mode was the AV-1 of 1979.When this camera appeared, a new type of FD lenses featuring instant mounting/demounting was also introduced, known as FDn or simply New FD, as according to official Canon brochures.

T-90 Camera Manual (Only available in HTML Format) (new) :| Canon 300TL Flash ; Canon A and T series SLR cameras. (new)

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Next, Canon's awesome program automation exposure control:

Program Automation Exposure Controls of the T90

In 1978, Canon launched its first fully automatic program AE mode camera, the A-1. Five years later, the 2nd camera with program AE mode was the AE-1 Program. Within the T series, the first model, the T50, has a built-in winder and Program AE mode incorporated within. The T50's P mode was also an improvement over those used in the A-1 and AE-1 Program as its algorithm used a new computing format that gave emphasis on faster shutter speeds when the light level gets lower. The next model, T70 has an LCD panel almost as big as the T90's and offered three Program AE modes, Wide-Program, Standard Program and Tele Program. You can just see how the development of Canon's Program AE has progressed prior to the T90.

This mode is designed to be easy to use and responsive. There's no denying that the advantage of Program AE has even made it to be popular among the seasoned pros. Program automation is gaining acceptance and its popularity had increased tremendously over the past 1-1/2 decades. Program AE mode is particularly useful when you are dealing with shooting condition that can change rather rapidly.

The T90's Standard Program AE mode allows the photographer to react swiftly enough to capture momentary images. The camera makes all exposure adjustments according to a standard program suitable for general photography where there are no special exposure problems. Both aperture setting and shutter speed are determined automatically, leaving the photographer free to concentrate on composing his shot. The Standard mode is the same as those used in the A-1 and AE-1 Program cameras.

There are two major program functions on the T90:
Standard program AE and Variable-shift Program AE with six other program controls.

The Standard Program AE mode is particularly appropriate for general shooting conditions, or for situations where you don't have time to compose your settings carefully. While Variable-shift Program AE Combines Ease of Operation with Creative Control.

The Variable-shift Program AE mode gives you both the easy operation of Program AE shooting plus a higher level of creative control. The T90's Program AE has 7 patterns of variable multi program AE. Depending on the kind of lens you are using, you can preset 3 TELE or 3 WIDE programs. Or, you can also opt to shift among programs as you shoot. In other words, you can control depth of field and shutter speeds even when taking advantage of the automated features of the Program AE mode.

You choose from
among its seven exposure programs: three small aperture-priority "Wide" programs, the Standard Program, and three high-shutter-speed-priority "Tele" programs.

The "Wide" programs are most commonly selected with wide angle lenses. They can be used to blur fast action or maintain maximum depth of field."Tele" programs employ faster shutter speeds to freeze the subject in time and isolate it against the background. They are especially suited for use with telephoto lenses.

With the T90's Variable-shift Pro gram AE, you can match the program with the lens used in order to get the exact results you want.

* Refer to the main map of T90 for cross reference.

Setting the Variable shift Program AE is fairly convenient for someone who has used a auto Multimode camera before . While pressing the Shooting Mode Selector, turn the Electronic Input Dial until "P" appears on the Display Panel. Remove your finger from the Shooting Mode Selector, then continue to turn the Electronic Input Dial until the desired program AE (any one of seven modes) appears on the Display Panel. The Variable Program AE modes of the T90 also reflected the shortcomings of the breech-lock FD lenses. These shortcomings were among the reasons why Canon has opt to completely redesigned the autofocus lenses intended for the EOS System with a fully electronic mount transmission type, enabling the AF cameras to utilize only one Program AE mode, the Intelligent Program AE.


Red numbers in the viewfinder indicate the shutter speed and aperture setting that the program mode has selected. By rotating the Electronic Input Dial while looking through the viewfinder, you can select the best combination for your shooting situation, moving toward a smaller aperture for greater depth of field or a faster shutter speed for stop action situations. Thus, even during shooting you maintain total control over the settings and can quickly change them in order to alter the final effect.

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Will bring you into the shutter priority AE and Manual settings

Note: PLEASE USE the MAIN REFERENCE 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.

Its Metering, Exposure control, Flash photography, Viewfinder display, Film Backs, Built-in Motor Drive, the brains, Focusing Screens Other capabilities and the eyes of Canon; Full specifications with details illustrations of its various controls, available in HTML / PDF (184K) format.

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