Canon AT-1

I have a current Canon EOS Digital camera and a few Canon EOS film cameras (EOS 5,  EOS 50, EOS 650) but they are all a bit too modern and plasticky for my taste. I have been on the look-out for one of the Canon FD mount cameras for a few years but they are either too expensive or have not aged well. When this camera came along, I was not sure what it was – I had never heard of the AT-1. It turns out that it is a Canon AE-1 without the automatic exposure system. As I do not like automatic exposure, this made the camera ideal for me.

• lens: Tefnon by Kobori
• focal length: 35-200 mm
• apertures: ƒ/3.5 to ƒ/22
• focus range: 1.7 m to infinity
• lens fitting: Canon FD breech-lock bayonet mount
• shutter: cloth focal plane
• speeds: 2 seconds to 1/1000
• flash: hot shoe plus PC socket
• film size: 35 mm

 This camera was advertised on that auction site for parts or spares. The seller stated that the camera was completely untested. The camera also came with a lens so if the camera was completely U/S I would still have a FD mount lens and could then take a punt on one of the many FD mount cameras around with no lens. Well, the camera is in excellent condition and works just fine. The only fault is that the foam light seals have expired and need replacing. As the camera is forty three years old, I had taken this as read! I also have the original manual which is a rare bonus.

At first glance, this is a very standard Japanese SLR. It is a similar size and shape to the Asahi Pentax Spotmatic series and slightly bigger than the (then) current Pentax ME Super or Olympus OM1n. The general lines of the camera are significantly cleaner than either the Spotmatic, ME Super or OM1 models. I like uncluttered so this appeals to me.

The top plate feels like metalised plastic. On the far right of the top plate is the film advance lever. This is anodised metal with a black plastic end. The lever is on a ratchet so the film can be advanced by a series of short movements. When not in use, the film advance lever sits over the top plate out of the way but when using the camera, the lever sits proud by 30º. The lever moves through 120º to advance the film one frame. This is both easy and fast.

Under the film advance lever is the shutter speed dial. This runs from two seconds to 1/1000 seconds plus B. 1/60 seconds is marked with a lightning flash to indicate that it is the flash synchronising speed. Beneath the shutter speed dial is the film speed dial. The is accessed by slightly lifting the shutter speed dial and turning. This is a bit awkward but doable with my large fingers. Film speeds are in ASA (which is effectively the same as ISO speeds)  and run from 25 ASA to 3200 ASA. This was a normal speed range in the mid 1970s and reflected the speeds of films in normal use. It is also a very usable range today.

To the left of the film advance lever is the shutter release button. According to the manual, this is a magnetic release so there is no mechanical link to the shutter mechanism (which is entirely electronic) so there should be less camera shake compared to those cameras with mechanically linked buttons. This button is a fairly large, black, metal button which is threaded for a standard cable release. This is showing some signs of wear as at times it does not work and sometimes it needs a very definite press. It has slightly improved with me dry-firing the shutter over the last few days.

Around the shutter release button is a three-position switch. In the A position, the camera is in its standard mode. In the L position, the shutter release button is locked so you cannot accidentally trip the shutter (this is more useful than you might think). There is also an S position. In the S position, the delay timer is activated. A red LED is exposed. When the shutter release button is pressed while in the S position, the red LED flashes for ten seconds before the shutter fires.

Behind this switch is the window for the frame counter. This counter resets to zero when the camera back is opened. It starts as S and when you have wound on the fogged part of the new film it will be at zero which is in red – all other numbers (just even numbers are displayed) are white apart from 20 and 36 which are also red. These (20 and 36) were the most common film sizes in the 1970s.

As is usual, the centre of the top plate is dominated by the pentaprism hump. On top of this is the accessory shoe. This is a hot shoe with an ISO standard central contact plus a single auxiliary contract specific to Canon’s range of speed light flashguns.

On the back of the pentaprism hump is the viewfinder eyepiece. This is rectangular, 16 by 10 mm, and has a grove on the outside which can accept an eyecup or auxiliary lenses for glasses wearers. Inside the viewfinder is the matt focus screen. In the centre is a ring of micro-prisms to aid focusing. In the middle of the micro-prisms is a split-image spot. These work by splitting vertical lines in the image. The more out of focus the image, the further apart the parts of the split image. As you focus, the parts come together and when the two parts are fully aligned the image is in focus. If there are no strong vertical lines in the image, that is when you use the micro-prisms.

On the right hand edge of the focus screen is the light meter readout. This is coupled to both shutter speed and aperture. The meter needle is a straight line and there is also  another needle which has a ring on top. To use the meter, you adjust the shutter speed and/or aperture until the meter needle is in the centre of the ring. There is no indication in the viewfinder of either shutter speed nor aperture.

Left of the pentaprism hump is the film rewind crank. This is a standard small folding crank. Around the rewind crank is the on/off switch. This has three positions – on, off and C. The first two are self-explanatory  – C is the battery check position. In this position, the meter needle in the viewfinder should be right at the top of its travel. If it is not, you need to replace the battery. The shutter is electronic so will not work without battery power.

In the middle of the front of the camera is the lens mount. This lens mount is the Canon FD mount. This is a three flange bayonet mount. It is unusual in that the flanges are outside the mount throat. The only other mount that I have seen like this is the Ihagee Exakta mount which has both internal and external flanges. The big advantage of external flanges is that it allows larger apertures for a given throat diameter. At the time that this camera was made, the FD mount was a breech-lock mount. What this means is that you place the lens in the mount and turn a locking ring to fix the lens in place. With most lens mounts, you turn the lens to lock it, rather than just a locking ring. Not turning the lens means that there is less (or no) wear on the linkages. Later on, Canon changed the mount so that there was no longer a locking ring and the lens turned instead as on other cameras.

The lens mount has to transmit information from the lens to the camera – and actions from the camera to the lens. At this age, the information is transmitted by levers and pins. What follows here comes from the AT-1 manual.

1. there is a screw which does nothing but is reserved for use in future developments.
2. a lever on the lens which transmits the set aperture to the light meter – this is mechanically connected to the lens aperture ring.
3. a pin on the lens which transmits the lens’ maximum aperture to the light meter.
4. a lever on the lens that closes the aperture when the shutter is fired. This is matched by a lever on the camera side of the mount which doubles as a depth of field preview.

The camera lever in 4 above can also be used with older lenses (FL series lenses which also fit this camera) or with close-up bellows or lens reversal rings. For these the meter cannot be used as intended  and using this sliding lever enables you to use stop-down metering.

Also on the right of the lens mount is a PC socket for flash. This enables you to use off-camera flash if you want to. On the left of the lens mount is the battery compartment. Opening this requires you to press a very small button recessed on the left of the battery compartment cover. This is quite awkward to do which is a fault on the good side. On either side of the camera, on the top plate, are strap lugs.

The rear of the camera has the opening back. The catch for this is released by pulling up the rewind crank. In the centre of the back, on the outside, is a holder for the end of the film carton so you can remember which type of film is in the camera. I do not understand why all film cameras did not do this. Also on the base is the button to allow the film to be rewound. This only needs to be pressed in as you start to rewind – there is no need to keep pressing it in. Also here is the tripod socket – 1/4 inch – either Whitworth or UNC, I am not sure of which was current in 1977.

The lens.

This camera did not came with the original Canon kit lens. Instead, the previous owner had replaced the kit lens with a zoom lens. This lens is marked as being a Tefnon lens. This is one of the brand names used by the lens maker Kobori. They are a mature Japanese company, founded in 1923 and still going in 2020. They have made lenses for Minolta, Sanyo, Nikon and Vivitar – that is, made the lenses for those companies, not lenses to fit their cameras. If the likes of Nikon are happy for Kobori to make Nikon brand lenses, they must be a good manufacturer.

The use of Tefnon as a lens brand dates from 1982 and, although Kobori are still making SLR camera lenses, the name Tefnon is now redundant. The serial number of my lens is 100785.

This lens is 35 to 200 mm zoom. with a maximum aperture at 35 mm of ƒ/3.5 and at 200 mm of ƒ/4.8. The minimum aperture if ƒ/22. The iris diaphragm has six blades giving a hexagonal aperture. The is a small button at the end of the aperture scale – pressing this allows you to turn the aperture ring a bit further to engage the auto-exposure setting. On a Canon AE-1 camera, this setting will allow the camera to select the aperture rather than just stop down to the user set aperture. As the AT-1 does not have any auto-exposure ability, it is not possible to set this lens to the automatic aperture setting.

The lens is multicoated and has a ‘macro’ ability. This ‘macro’ ability offers a 1:5 reproduction ratio so an object that is 25 mm across will for an image that is 5 mm across. This is far from real macro – purists would expect a 1:1 reproduction ratio – but the lens does focus down to around 600 mm.

At the moment, the camera is not useable as I need to replace the foam light seals (not a hard job) but when I have have done so, I shall be testing this camera and lens and reporting the results here.

First Film Test.

Above, I stated that the foam light seals need replacing. In an ideal world, I would have replaced these before testing the camera with film. I got impatient and tried the camera with the old, sticky, foam seals in place. On some cameras this does work well, but not on this one. There are rampant light leaks and on a roll of 24 exposures, only three were any good. I am displaying a selection of these below. It would seem that the main light leak comes from the hinge of the back – the foam here has degenerated to virtually nothing. The evidence for this is that the light flare on the film extends vertically from one edge of the film to the other. If the light was leaking from the top or bottom edges of the back, the light flare would be horizontal.

What I can say at this point is that the lens works well, the light meter is at least reasonably accurate, the shutter moves smoothly with no sticking or juddering and, in general, all seems to be well apart from the light seals. My next job is to actually replace the seals with the foam I have on hand (it is readily available on the auction site and probably elsewhere) and test the camera again.

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I have now replaced the light seals and run a second film through the camera. Everything is now working well. Here are a few of the test pictures with good light seals.