Testing the shutter and meter of a Canon F-1

by Tom Scott

The goal of the test is to check shutter operation and timing, and the meter. There are three objectives to the test:

1. Verify relative meter linkage for both reading accuracy and consistency from one shutter speed/aperture setting to the next. The meter itself is electrical and may be easily adjusted by a technician, but the mechanism that affects the ring and needle in the viewfinder is spring and cable operated. If any of this gets out of adjustment, your repair is more difficult and expensive, and should only be touched by a good technician with F-1 experience.
2. Relative shutter speed accuracy. The only way to precisely measure speed is in the shop with proper equipment, but this method will at least tell you if you are close and if the shutter mechanism is off from one speed setting to the next.
3. Proper shutter curtain operation. This is particularly important at shutter speeds of 1/60 and slower. You will see if either curtain is sticky or if you have any curtain bounce.

Do the following before you perform the test:

1. Your lens and aperture mechanism must be in good operating condition. With the lens on the camera, put it in stop-down mode and operate the lens aperture ring. It should move smoothly and the aperture blades should open and close. The blades should also be clean and free of oil. Take it out of stop-down, put the lens on its highest aperture setting, open the film cover and operate the shutter release at 1 second while looking through the back of the camera. Observe that the shutter curtains operate smoothly and the aperture stops down smoothly to a small hole. This is not a definitive test, but if you see any problems, then either the lens or the camera body has a problem that must be corrected before proceeding with the test.
2. Run through the following settings while looking through the viewfinder: 1/500@f5.6, 1/250@f8 1/125@f11, 1/60@f16, 1/30@f22. The needle and ring should stay in exactly the same position throughout the range of settings.

If you have any problems with the above, replace the lens for Step #1. If Step #2 shows variation, you will need to take it to an experienced F-1 technician to have the meter linkage repaired and adjusted.

Try to use a fixed focal length lens that has an aperture range of at least f2.8 to f22. Otherwise, you may not be able to adequately test slower shutter speeds.

Buy a 36 exposure roll of Ektachrome or any other good slide film. Try to find something around 50 asa and use a 36 exposure roll since you must run the entire test on only one roll. If possible, go to a professional camera or photo shop since the film will be fresh and handled properly. Do not use print film since it has much wider exposure latitude than slide film and will not show you small variations in exposure that you must be able to see.

I perform the exposure test outside on an overcast day and use the film box's exposure guide for initial settings. These are pretty accurate. Try to do it around noon, since that will be closer to the conditions the film guide is based upon and you will have less change in sun angle and intensity during the test. The subdued conditions will keep lighting and shadows consistent, and will give you a better setting range for your lens aperture. Choose a subject that is of uniform color and shade. I use an off white wall on the side of my garage. The idea is to see variations in exposure and across the photographed surfaces. The whole test shouldn't take more than 5 minutes once you have it set up.

The following assumes that exposure recommendation for 50 asa is f16 @ 1/60 second. Verify this and adjust the table and your test accordingly. This equates to f2.8 @ 1/500 sec., which is my starting place. I almost never shoot faster than that and I assume that moderate shutter timing error probably won't be significant.

I then make a chart as follows:

1. Set the camera on a tripod and use a shutter release cable to make exposures. It is important that you have sharp images at all settings.
2. Be sure that you have your film speed set correctly on the camera, your aperture is set at f5.6 + 1 stop (f8) and your shutter speed at 1/500.
3. Make exposures quickly and carefully in the order shown on the table.
4. Wait until you have lower lighting conditions, then make exposures at lower shutter speeds at the appropriate f-stop. It is assumed that your exposure settings will be close to correct. We are not worried about accurate exposure on these frames.
5. Send the film in for processing. Be sure that you tell them process only, do not cut and mount film.

When you get the film back, use a magnifying glass or film loupe to view the film. What you should see is a series of 4 complete and 1 incomplete series of frames, each going from underexposed to overexposed. It will be easier to view the results if you cut the film so that you have strips of frames 1-5, 6-10, 11-15, 16-20 and 21-23. It is not important how you cut the remaining film.

Viewing the results

Because you used slide film, you should be able to see a slight incremental, but visible, increase in exposure from 1 stop underexposed to 1 stop overexposed. The strips should appear exactly identical to one another. Line the strips up in a column with one above the next. The last series strip with only 3 exposures should on the bottom and right hand justified with the other strips. If everything is perfect, the center exposure on each strip should be right on the money, and form a column of exposures 3, 8, 13, 18 and 21 that are identical. The vertical column of frames 1, 6, 11, and 16 should also appear equally underexposed and so on.

If the center exposures on the strips are identical, but not properly exposed, you likely have a meter problem.

If there are any variations between center exposures, you probably have a shutter problem.

Carefully study the center exposure on all strips and also the other exposures taken at shutter speeds below 1/30 with a magnifying glass or loupe. What you are looking for is any variation from one side of the frame to the other. It may appear as a darkened vertical band at one side of the frame or the other. If you see that, or any other defect that is vertical and extends all the way from the top to the bottom of the exposure, then you have a shutter curtain problem. The defect will be more visible on speeds of 1/60 and slower. It is very unlikely that the camera can be economically repaired if this is the case. I had the problem and the camera shop had to find a complete, good used shutter mechanism to put in my camera. It did not cost me a fortune, but only because they mis-diagnosed the problem to begin with and stuck by their original repair quote.

Chances are, you will find what I did. Everything was uniform, but off by ½ stop. This was due to the meter and was never fully repaired. The ultimate solution was to simply take all of my ambient light photos at +½ stop. I eventually tired of that, plus I wanted a spot metering capability. I solved the whole thing by buying a T-90 on Ebay which gave me a camera with built in spot metering capability, motor drive, built like a tank and would take my FD lenses. It was the right move and I do not miss the F-1 at all.

The article above was written by Tom Scott in response to miscellaneous questions about the Canon F-1 posted in the Canon FD area of Photo.net by various people of whom Peter Evans was merely the most recent (December '01). That explains the references to the Canon F-1; perhaps with minor changes, the advice should prove equally useful for testing various other cameras. Tom kindly gave permission for it to appear at http://hoary.org/snaps/camtest.html (where it was first posted on 15 December 2001), but retains all rights to it. Questions about the page -- its content, or the possibility of reproducing it elsewhere -- should be mailed to Tom Scott. (Note to the litigious: Tom has provided the information free of charge and in good faith; if anything you read or imagine within it causes you to lose patience, hair or money, don't bother to contact an attorney; just sit back and relax with a beer.) None of the numerous photos on this website was taken with a Canon F-1, so don't blame that fine camera for the poor quality. Meanwhile, you can view Tom's work with his Canon T-90 at his Battleship Texas Photo Tour.