McLarenblog

Troubleshooting the obvious and less obvious:

Camera will not run.

• Check to make sure the motor clamp is snug. The camera motor body is the return electrical path and must be touching the motor housing clamp tight enough for a good electrical contact.

• The film buckle switch might not have been set properly. Open the sprocket wheel mechanism and then close. You don’t see it but a little plunger resets the film buckle switch to the “ON” position by open and closing the thread mechanism.

There are times when the film buckle switch just will not set properly. There is a small pin that is the film buckle switch over ride. This is another switch that bypasses the film buckle switch to allow the camera motor to run. In theory the film buckle switch will shut down the camera when a film frame is not advanced but the internal sprocket wheel continues to pull film out of the film pressure plate. When a couple of frames are not moved forward out of the aperture then the bottom or take up side film loop will diminish thus putting pressure upon the pressure plate. Inside the camera is a small roller that is located below the sprocket wheel and in the path of the bottom film loop. When that loop shrinks in size due to missing film frames, this roller will be pulled upward and trigger the film buckle switch thus shutting down the camera. Some times it is imperative that the last take be protected and the camera operator needs to wind a turn of film forward to protect the last shot. The film buckle over ride switch will allow you to do this. Just press in on the little pin near the on/off switch and then turn the camera on. Note: The film buckle over ride switch allows you to determine if the film buckle switch remains off even when you reset it.

• The original Arri S power cable typically breaks an internal wire within a very close distance from the camera. With no film loaded, press down on the power switch and try to move the power cable up toward the camera or if that fails any direction. If you discover that the camera power cable in intermittent and you have to use the camera in the field, determine the best means of taping the cable so it will run. Note: Some institutions and rental houses have modified their cameras to avoid using the original Arri power cable as they are exceedingly hard to find and if you find one are usually over priced.

You can not see an image.

• Obviously, there is a lens cap and I would hope that that cap is not on the front of the lens.

• The viewfinder might have a cap over it. Swing the cap out of the way. Some cameras have an automatic iris that closes out the light from the viewfinder unless the operator places his or her eye up to the viewfinder and presses against the eye cup. The pressure opens the iris and allows the operator to view and image.

• Each lens has a iris adjustment. Rotate the iris ring to full open.

• The viewing mechanism employs a front surfaced mirror to direct the lens image to the viewfinder while the film is being pulled down inside the camera. It is a 50/50 percent chance that when the camera is stopped that the shutter is open allowing the lens light to the film but denying you the ability to see anything from the camera viewfinder. The solution is simple. Just rotate the camera motor shaft a bit, that is the little knob at the rear of the motor until you see the image.

• Are you using a telephoto lens or zoom in full zoom in setting? It is quite possible to be so closely zoomed into a blank wall or other surface that nothing will appear in the viewfinder. Pan or choose a wide angle lens.

• The camera has three lens mounts. Make sure that you do not have the lens turret set between lenses. If you are not using all of the lens cavities, you are expected to put in a lens cap type of plug to block light and dust from entering the camera. Make sure you have not turned the lens turret to where there is no lens but a plug.

Image is out of focus.

• Did you set the diopter first? Setting the diopter is the first step you should complete before thinking about using any lens. Just take the camera with or without a taking lens and shoot something blank like a white wall, the north sky if outside, or the sidewalk. Concentrate on a ground glass image in the viewfinder. Make darn sure that that ground glass is as sharp as you can make it for your eye by rotating the diopter ring close to the eye cup. Most Arri S cameras come with a target on the ground glass which makes finding ground glass focus pretty easy. It is possible to come across a camera without a target scribed into the ground glass surface. Just concentrate on the ground glass grain until it looks as sharp as you can get it. Whenever any camera person uses the camera, that person and only that person must reset the diopter. Never set the diopter for another camera person!

• Now that the diopter is properly set, do not change it but lock it in place using the viewfinder lock ring.

• Take the lens you intend to use and set it to infinity focus. The infinity marking on a lens is a figure “8” laid on its side. Infinity is a fantastic way to calibrate a lens or check its calibration.

• Take the iris ring found on the lens and open it ALL the way. Do not stop it down one little bit. It must we wide open to remove any depth of field. [Dept of field is the area between a near and far point from the lens that shows acceptable focus.]

• Through the viewfinder, look at an object with fine thin lines at infinity. Now lets get real here. Just pick an object at least a quarter a mile away. Power poles, power lines, high rise buildings with windows, edge of a tall building, tall trees, etc are really good objects to pick. Now we are going to concentrate on the fine lines of one of the far distant objects. Rotate the lens focus ring and rock the ring back and forth until you get the best focus.

• Is the image sharp? Take into consideration that the image is composed on to a ground glass and the image by definition can not achieve any fantastic detail with this method but it should look sharp.

• Look at the setting of the lens focus ring. Is it right on the infinity mark? If it is not, either you did the diopter adjustment wrong or the lens is out of calibration.

Image seems out of focus (more rigorous check).

• Obtain a Siemens star target and place it at a convenient distance from the lens. This will require that you also have a tape measure. Look at the lens and look at the lens markings for distance. Choose a distance from the camera corresponding to a mark found on the lens. For example a lens mark might show 10 feet. If a lens is set to be in best focus at 10 feet but is not when we look though the viewfinder, then there is an error. If we choose 10 feet for the Siemens star then place that star image 10 feet from the camera. Most cameras have a film plane marking to indicate distance measurements. On the Arri S is on the opposite side of the operator close to the matt box attachment. The mark looks like a circle with a line running through it. One of the tape measure should be placed at that mark. Place the target Siemens star at a precise distance from the camera which is the
  SAME as the distance you set on the lens.

• Perform the viewfinder ground glass focus as described above. Make darn sure this is as precise as you can get. If you get the ground glass calibration wrong this whole method falls apart.

• Now open the lens all the way. We want minimal depth of field.

• Rotate the focus lens ring back and forth to make the Siemens star appear as sharp focus as you can get. If you had chosen 10 feet, you will be rocking the focus ring closer than 10 feet and further than 10 feet to find the best, sharpest Siemens Star Chart image. Please remember that ground glass focus method is not going to be immaculate because the ground glass will soften any image. Just concentrate on the lines you see in the lens of the Star Chart and stop when the target gets sharp. The beauty of the Siemens Star Chart is that the center of the target goes out of focus in a hurry with any small deviation from perfect focus.

• Now with the lens left where you found the best focus, compare the lens focus ring reading to the measured tape distance of the Siemens star to camera film plane distance. The two distances should be within four inches of each other. It they are not then a problem exists with the camera or the lens. Do not use the camera but return it to checkout or rental house and tell them that the tape vs eye measurements do not coincide.

Tip: Perform this procedure a few times and to see that you get the same results.

Obtain Siemens Star Chart   It is a good idea to take the printed Star Chart and glue it to a flat surface that you can carry around with you.

NOTE: Lens back focus is different with each model camera. Lens back focus is the distance behind the lens where the real sharp focus occurs. This sharp focus must occur on the film emulsion as it sits in the film camera aperture. Occasionally we send in our zoom lenses for collimating. We provide a camera with the lens. Some zoom lenses are matched for a particular camera. In addition, an exact lens opening on the turret is optimum and sometime comes with a special marking. For most student projects you should not care which zoom lens goes with which camera. In the professional field you will take great care that the lens properly matches the correct camera. In any case, do not use lenses intended for another camera as the back focus might and probably will be wrong.

The information here is for educational and reference use only. Decide on your own how to proceed in performing any repair you face. We do not accept any responsibility for this information being entirely accurate. We hope it is accurate. Most of the information posed here has been noted to be significant, used in the repair process, and to some extent tested for accuracy through the actual discovery and recording of performing a repair. If you decide to use any of the information here, try to keep in mind that a number of factors may change when you attempt the “same” repair. Models do change from apparently being same units. Their are definitely different methods of making a repair. The steps that you should use to achieve a successful and expedient repair might be different. The problem you face with a piece of equipment might be similar but not an exact match to what we faced. Just use common sense and always be a bit skeptical of following our methodology until you feel that you and we share the same viewpoint and tactics.