Canon T90

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The Canon T90, introduced in 1986, was the top of the line in Canon's T series of 35 mm Single-lens reflex (SLR) cameras. It was the last professional-level manual-focus camera from Canon and thus the last of them to use the Canon FD lens mount. Although it was overtaken by the autofocus revolution and Canon's new, incompatible EOS (Electro-Optical System) after only a year in production, the T90 pioneered many concepts seen in high-end Canon cameras up to the present day, particularly the user interface, industrial design, and the high level of automation.

The T90 gained the semi-official nickname The Tank from Japanese photojournalists because of its ruggedness^[1]. Many still rate it highly even 20 years after its introduction: camera collector and dealer Stephen Gandy^[2] states, "…the Canon T90 was years ahead of anything else on the market at that time. It is, quite simply, one of the best manual focus 35 mm SLR designs of all time." He goes on to conclude, "It gets my vote as the best Canon Design ever." Similar sentiments can be found from many other users.

Contents 1 Design 2 Power features 3 Metering 4 Exposure 5 Flash 6 Accessories 7 Modifications 8 Use today 9 See also 10 Notes 11 References 12 External links

[edit] Design

Previous Canon cameras had been wholly in-house design projects. For the T90, Canon brought in German industrial designer Luigi Colani in a collaboration with Canon's own designers^[3]. The final design was a composite of Colani's ideas and the Canon team's, incorporating Colani's distinctive "bio-form" curvaceous shapes. Canon considered Colani's contribution important enough to present him with the first production T90 body, engraved with his name. Computer-aided design techniques were introduced to Canon for the T90, as well as the use of computer controlled (CNC) milling machines to make the molding dies for the shell.

Much work went into human factors engineering to create an ergonomic user interface for the camera. The form of previous cameras was largely dictated by the required locations of mechanical controls on the body, such as the film advance lever, rewind crank, shutter speed dial, shutter release, etc. On the T90, the film transport controls were no longer required, while the others were no longer mechanically linked. This gave the designers more freedom to shape the camera to make it easier to control and hold, and to place controls in a way that suited the user rather than a mechanical design.

The T90 introduced features still used on SLR cameras today, such as the deep right handgrip with the shutter release button positioned atop the grip rather than back on the body. While the use of a LCD screen on the top of the camera's right hand side was not new for the T90—it was introduced on the T70—the T90 refined it to show even more camera information. A control wheel located behind the shutter release and convenient for the right index finger was used to adjust most camera settings in conjunction with other buttons located for the right thumb and on the left-hand side of the camera; again, this design is still seen today.

[edit] Power features

The T90 came with an integral motor driven film advance, focal plane shutter, mirror and aperture cocking and rewind functions. Canon broke new ground with the powered features of the camera. Previously, cameras used one powerful electric motor geared to all functions. Instead, three coreless micromotors were placed within the body close to the functions they drove for maximum mechanical advantage. One was used to wind the film, achieving a high-speed rate of 4.5 frames per second. A second prepared the shutter, mirror etc. for the next shot. A third motor powered the rewind function. All of this was driven by four AA batteries in the base of the camera.

To control the camera's systems, the T90 used a dual CPU architecture. The main, low-power CPU ran at 32 kHz while the sub-CPU ran at 1 MHz, and was powered down when not needed. The main CPU handled the LCD display and overall state, while the sub-CPU handled exposure calculations, viewfinder display, and control of the camera's motors. This architecture provided for lower power usage. Both CPUs, plus other integrated circuits and components, were mounted on several flexible circuit boards that fitted around the camera's structure.

A coin-type lithium battery on the main circuit board retained camera settings with the AA batteries removed. This was not a user-serviceable part, and when it failed the camera had to be brought to a service center where the battery could be replaced by a Canon technician^[4]. Expected battery life was on the order of five years, although this depended on a variety of factors including how long the periods were of being without main battery power.

[edit] Metering

For the T90, Canon developed their most sophisticated light-metering system yet. Although it introduced no novel metering techniques, it assembled the majority of the metering techniques then developed into one easy-to-use system. First, it took the metering options from the New F-1—center-weighted average metering, partial area metering, and spot metering—and made them available with a press of a button and a turn of the command dial. The New F-1 required a focusing screen change to switch metering patterns. On the T90, partial area metering used the center 13% of the picture area, while spot metering used the center 2.7%.

To these, Canon copied the metering options found on Olympus' OM-4 ^[5]. Multi-spot metering allowed the photographer to average up to nine spot meter readings from different parts of the scene. In another feature borrowed from Olympus, separate Highlight and Shadow spot readings could be taken. These adjusted the camera's metering decisions to ensure extremes of tonal range were not muted and grey in the final exposure.

Two built-in sensors were used to implement all these metering options. Center-weighted and partial area metering were performed by a double-area silicon photocell (SPC) in Canon's standard location above the eyepiece, while spot metering was performed by another SPC located at the bottom of the mirror box. Light reached that sensor via a half-silvered area of the main mirror and a secondary mirror located beneath it. The spot metering cell also allowed for automatic TTL "off-the-film" flash metering, again borrowed from Olympus.

Notably lacking was what is now the most common metering mode on SLR cameras, matrix metering. Nikon had introduced this in the FA in 1983, but Canon did not follow suit until 1987's EOS 650.

[edit] Exposure

Eight exposure modes were available. Program AE (Auto-Exposure) mode put exposure control completely in the hands of the camera. Variable Shift Program AE allowed the photographer to bias the camera towards narrow aperture with 3 Wide Angle settings, or fast shutter speed with 3 Telephoto settings as well as the standard mode. For more manual control, Aperture Priority AE and Shutter-Speed Priority AE allowed the photographer to set one exposure variable manually while the camera chose the other.

In either of the latter two modes, a Safety Shift feature allowed the camera to adjust the "fixed" parameter if it could not obtain a correct exposure otherwise. For example, in Aperture Priority mode, if the photographer had the aperture fixed wide open to photograph a very bright scene, the correct shutter speed to expose correctly at that aperture might be faster than the camera was capable of. Safety Shift would let the camera reduce the aperture until it could achieve a correct exposure at maximum shutter speed. The Safety Shift feature could be turned on and off by pressing two buttons on the back of the camera near the base.

If no automation of exposure was desired, a Manual mode was available. In this, the camera's metering acted as a sophisticated light-meter, but all decisions were made by the photographer. For use with older lenses that did not have an automated aperture diaphragm, Stopped-down Aperture Priority AE or Stopped-down Manual could be used; these instructed the camera that the currently set aperture would be the taking aperture, and to therefore adjust the metering calculations accordingly. Finally, a Flash AE mode was available for flash photography.

[edit] Flash

The T90 was the first Canon camera to support through-the-lens (TTL) flash metering. This measured the actual light levels reaching the film by measuring reflected light off the film (OTF), shutting down the flash unit once the film is sufficiently exposed. The measurement is calculated using the average reflectivity of color negative film. This system was also used on Canon's new EOS system, making the T90 the only non-EOS Canon body compatible with TTL Canon flashes^[6]. The T90's X-sync speed of 1/250 second was the fastest Canon had achieved and was better than most other cameras available at the time.

A new, dedicated flash unit, the Speedlite 300TL^[7], was launched alongside the T90 to support its new flash modes. It had a zoomable head, capable of adjustment (by moving the head in and out) to cover the fields of view of 24, 35, 50 and 85 mm lenses. For bounce flash, the head could be rotated up to 90° vertically, 180° to the left, and 90° to the right. As well as the plain TTL mode, the 300TL supported A-TTL (Advanced TTL); here, the flash-to-subject distance was calculated using an infrared pulse with a detector mounted on the flash body. In bounce mode, however, it used a 1/20th power pre-flash instead.

A pre-flash was also used in FE Lock mode (flash exposure lock). Here, the pre-flash was used in conjunction with spot metering to determine the correct exposure in advance of taking the picture. Thus, the camera could be moved to reframe the main subject off-center and still expose correctly.

For exposures slower than the X-sync speed, previous SLR flash systems triggered the flash at the start of the exposure, as soon as the first shutter curtain had finished its travel. However, for motion blurs and light trails in a longer exposure, this gives the impression of backwards movement, since the motion trails out in front of the moving object after the flash. The T90, for the first time in a mass-market camera, supported second-curtain flash, where the flash fires at the end of the exposure, just before the second shutter curtain starts to close.

Canon also produced a dedicated macro ring flash for the camera, the ML-2. This supported TTL and manual models only, and contained two flash tubes, one on either side, which could be fired separately or together. The system consisted of the flash ring itself, which fitted onto the end of the lens, and a control unit which screwed into the hot shoe atop the camera. The later ML-3 ring flash, introduced for the EOS system cameras, also supported the T90.

[edit] Accessories

While the T90 did not support the vast range of accessories available for Canon's F-1, F-1n or New F-1, a number of significant accessories were available. The pentaprism was not interchangeable, but the focusing screen was; eight different screens were available for different applications. Standard was the New Split/Microprism screen, which offered three of the most common focusing aids simultaneously; the central circle was a split image prism, surrounded by a microprism ring; the rest of the screen was a laser matte.

Two optional data backs were available for the T90. The first, the Command Back 90, both allowed date and data imprinting on the photographs and also allowed various forms of time-lapse photography. The second, available only in certain markets, was the Data Memory Back 90, which stored 16 shot variables for up to 156 exposures, or six variables for up to 338 exposures. The computer interface to the Data Memory Back 90 supported only the MSX home computer standard^[8]. Third parties have adapted connectors to other computer systems.

A wired 60T3 remote control unit plugged into a socket fitted beneath the right handgrip, while an infrared remote control kit was also available as the LC-2. This unit also supported an Auto Sensing mode for completely unmanned photography. This tripped the shutter whenever something blocked the path between transmitter and receiver—useful in wildlife photography, for example.

[edit] Modifications

A number of modifications to the T90 have been performed over the years, by Canon or third parties, in order to add features missing from the camera as-built:

• PC flash sync socket: The T90 lacked a separate flash sync socket. The addition of one could be performed by request by Canon support centers. It was fitted on the left-hand side of the prism housing, as seen by the user.
• Vertical shutter release: actually an accessory, since it required no camera modification. A vertical shutter release, convenient to the right index finger when holding the camera vertically, was available from Canon Professional. It fitted into the remote control socket on the camera at that location.
• Mirror lock-up: Canon considered the mirror in the T90 sufficiently damped as to need no mirror lock-up feature. Many users disagree, and instructions on how to modify the camera to add this feature are available^[9].
• Leader-out film rewind: Photographers who like to change film mid-roll prefer the film leader to be left out when the film is rewound, so they do not have to fish for it with a leader retrieval tool. Instructions on how to perform a modification to enable this are detailed online^[10]. Since the modification consists only of connecting two solder pads on a circuit board with a wire, clearly the capability was built in to the camera's electronics but not enabled.

[edit] Use today

As of 2006, the T90 is 20 years old. Canon ceased supporting the camera in 1998 and spare parts are no longer available from them. The subsequent difficulty in obtaining repair services is likely to discourage any remaining professional use of these cameras. Users report that the cameras continue to be quite reliable, with two exceptions.

The first is with the LCD display and is not unique to the T90. LCD displays age and wear out at a varying rate dependent on environmental conditions, use and other factors. Commonly quoted lifespans are about five to ten years^[11]; thus, many T90s will have displays nearing the end of their lives, even if they have been replaced. The spare part is no longer available and no third-party replacement has emerged.

The second and more serious problem concerns the shutter. The T90's shutter appears to develop a 'sticky' nature as the camera ages. It is prone to locking up, in which case the camera's LCD displays "EEE" and the message "HELP" appears in the viewfinder display. This is commonly called the "EEE syndrome" among users. The problem is most likely to crop up after the camera has been left unused for some time; thus, the best way to prevent it is regular use of the camera. It does not seem to cause inaccurate shutter speeds before failure. The problem can be corrected by a knowledgeable technician without replacing the shutter mechanism. It is reportedly caused by dirt on the shutter's magnets affecting their performance.

Canon T90s fetch reasonably good money on the used market. Prices from used camera dealers providing warranties range from approximately US$150 for a camera in poor condition to approximately US$700 for a camera in "as new" condition with box and all original accessories and manuals. Most examples in reasonable shape fetch US$250-350. Prices on auction sites such as eBay are lower.

Canon FD lenses, however, remain quite affordable compared to their EF counterparts^[12].

[edit] See also

• List of Canon cameras

[edit] Notes

[edit] References

[edit] External links

• Canon Inc. (1986). Canon T90 Service Manual. (PDF). Retrieved from the Canon FD Documentation Project.
• Canon Inc. (1985). Canon Command Backs 70/80/90 Manual. Retrieved from the Canon FD Documentation Project.

Canon SLR cameras
Lens Mount	Series	Model
FL		FX (1964), FP (1964), Pellix (1965), FT QL (1966), Pellix QL (1966), TL (1968)
FD	F	Amateur: FTb (1971), FTbn (1973), EF (1973), TLb (1974), TX (1975)
		Professional: F-1(1971), F-1n (1976), New F-1 (1981)
	A	AE-1 (1976), AT-1 (1976), A-1 (1978), AV-1 (1979), AE-1 Program (1981), AL-1 (1982)
	T	T50 (1983), T70 (1984), T80 (1985), T90 (1986), T60 (1990)
EF
	1	EOS-1 (1989), EOS-1N (1994), EOS-1N RS (1995), EOS-1V (2001)
		EOS 650 (1987), EOS 620 (1987), EOS 750QD (1988), EOS 850QD (1988), EOS 630QD (1989), EOS RT (1989), EOS 700QD (1989), EOS 10sQD (1990), EOS 1000F (1990), EOS 100 (1991), EOS EF-M (1991), EOS 5/5QD/A2/A2e (1992), EOS 1000FN (1992), EOS 500 (1993), EOS 888 (1993), EOS 50 (1995), EOS 500N (1996), EOS-3 (1998), EOS 88 (1999), EOS 300 (1999), EOS 30 (2000), EOS 3000N (2002), EOS 300V (2002), EOS 3000V (2003), EOS 30V (2004), EOS 300X (2004)
	IX	EOS IX, EOS IX Lite
		Canon DSLR cameras
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