Modern Classic SLRs Series :
Canon F1 - Booster T Finder - Introduction


Canon F-1 Booster T Finder.Image (16k Jpeg)

Canon Booster T Finder

Sections outlined in this site
for Canon Booster T Finder

Specifications and Various Controls
Basic instruction/attachment
Instructions / Handling / Operations

All three sections have a html format and supplement with a Pdf file for download.

* Others Prisms/Finders for Canon F-1 are:
Waist Level, Speed Finder & the Servo EE Finder, and a Electronic finder...

just Download an
Instruction Manual - courtesy of Mr. Christian Rollinger

Relative: The Booster from the Pellicle Mirrored Canon Pellix QL, 1965.

Between the Servo EE Finder & the Booster T Finder, this is more straight forward. Its main function is to expand metering of the CanonF-1 to lower light levels. The CdS built in the camera body is limited in metering ability, and is not sufficient to perform light metering under dark conditions. In order to solve this problem, the Booster T Finder was developed to replace the standard pentaprism. Since the viewfinder of the FT and FTb camera is not interchangeable, an attachment type Booster is also available.

There are two levels of "darkness" in metering. One is when illumination is dim, (at night, early dawn, and at dusk). The other is although when sufficient illumination is available, little illumination reaches the film plane because of lens extension in close-up, macrophotography and photomicrography. The Booster T Finder extends the metering ability under darker conditions so that exposure can be set by TTL in either of the above cases. Interpretation of the scale of "darkness" expressed as –3:5 EV with film of ASA 100 is that under ordinary moonlight. Under the light-of the full moon, the EV value is –1. When the exposure is set by light metering with the Booster T Finder, a surprising effect is gained and the picture that shows the night scene is as bright as daytime. Since they are necessary factors for photography under dim-light condition,
the shutter speed ranges from 1/60 to 60 seconds and ASA setting is possible up to 12800 with the Booster T Finder. And for long-time exposures of more than 3 seconds, the electronic timer automatically controls exposure time by holding the shutter release button during exposure. Another more important and convenient feature is that the operation with the Booster T Finder can be extended from dark conditions to bright ones, thus user doesn't have to keep on changing the finders. This is accomplished automatically switching the metering to the camera body.

* (But remember, exposure under a second needs to do some compensation for Reciprocity failure for the film - even the metering is done TTL.

Metering Mechanism
| Metering with Booster T Finder | Metering with Camera | As the same way of how the Servo EE finder works. This viewfinder adopts the average method system with two CdS placed at each side of the eyepiece and gives priority to the central area, though the F-1 body adopts central area metering method. The Metering range is from EV 15 to EV–3.5, the exposure range being from 1/60 second at F 22 to 15 seconds at F 1.2 using ASA 100 film. The metering automatically switches between the camera and the Booster T Finder. The camera covers from EV 15 to EV 3, and the Booster covers from EV 10 to EV–3.5. This results in the overlapping of some areas which makes it more convenient. Light metering by the camera for bright areas is the same as in the ordinary full aperture metering system with aperture fully opened for the FD lenses and stopped down for the FL lenses.

Frontview.jpg BackView.jpg
When light metering is conducted by the Booster side, the aperture must be stopped down to maintain the quality of operation, and to preserve the characteristics of the CdS. The window for reading the outside meter is used with the zero speed.
When metering is conducted by the Booster, the electronic timer, considered as the main feature, functions to lock long-time exposures from 3 to 60 seconds in the low light range. While the timer is operating, a small lamp blinks at intervals of 1 second until exposure ends. This long-time exposure setting will control the Booster when the shutter dial on the camera body side is set at B. The eyepiece shutter is provided to prevent light coming through the eyepiece from affecting the meter. When this shutter is opened, the Booster T meter will not function.

Viewfinder Information This viewfinder has a pentagonal prism, the same as the eye-level viewfinder, and its field of view and magnification are also the same as those of the eye-level viewfinder. However, the light metering mechanism is designed to work either from the camera body or from the Booster T Finder according to which way it is switched. The contents of the viewfinder information will vary depending on where the light metering is performed. In light metering from the camera body, as it is the ordinary full aperture metering, meter information built in the F-1 body is designed to be read off with illumination provided by a lamp built in the Booster T Finder. When switched to light metering from the Booster T Finder, the meter information window will not be visible without the lamp which stops illuminating because the camera meter is not needed. On the other hand, a different lamp, located at the top of the pentagonal viewfinder, to read information for light metering from the Booster lights up.

Power Source * More detailed Instructions/Handling with the Booster T Finder | At normal temperatures, the Booster T Finder works continuously for some four hours with the No. 544 6V silver oxide battery. However, at low temperatures power will decrease, and as an external electric source is needed, the battery case which contains the Battery Magazine 12V, the exclusive 6V 2B Cord, is provided. When using the Booster T Finder for a long time in cold climates, these batteries are highly recommended.

Note: AS these finders are quite "Technical" in handling, please use the comprehensive sites we provide here for detailing of how to use these finders and its accessories within the Canon F-1 system.

Also check: The Servo EE Finder | Speed & Waist Level Finder |

Concept | Reliability Issue | Motor Drive Units | Macro | EE Servo / Booster Finder | Bulk Film Back | CAT (Flash System | F1 High Speed | ODF-1 | Placid | Assembling Diaphragm | Canon FD & FDn lenses

| Back | to Main Index Page of Canon F-1(n)

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| Message Board | Specifically for Dispose or Looking for Canon Photographic equipment

Other Canon Resources: If you have a New Canon F-1...
Canon FD Lenses Site | Canon A and T Series SLR models


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