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I have two Polaroid Land Automatic cameras (a 360 and a 250).  Although the 360 works pretty well, there is no easy way to connect it to a flash.  On the other hand, the 250 has a nice, standard PC port, but has exposure problems.  Specifically, when the camera is used in very bright environs, the images come out completely black.  I figured this must be a problem with the exposure meter, since the autoexposure system is pretty old and can probably no longer be trusted.

There are two possible causes for erroneous exposure calculation.  In the first, the photocell may be too old, and exhausted, and needs to be replaced.  This may true for my 250, but there is little I can do about it, so I decided to ignore that possibility.  The other possible cause is that there is something wrong with the timing of the shutter curtains (or blades, in this case) which can result in the exposure values being off.  I tried to fire the camera while shining a flashlight directly into the photocell to simulate the brightest exposure, and found that the aperture does not open at all.  Since the first curtain is released mechanically, and appears to move freely, it became apparent that the second curtain, which is released when the electromagnet (circled in blue below) is demagnetized, is the source of error.  I fired the shutter many times, and realized that under the brightest conditions the electromagnet does not seem to be magnetized at all, and the two curtains are released simultaneously.

Adjustment screw (red circle) and electromagnetic shutter control (blue circle)

I know that these cameras usually come with ways for the technicians to adjust the shutter speeds, since no photocell is ever made perfect.  There was only one set screw (circled in red) that was visible.  Not wanting to tear down the camera any more, I tried adjusting the screw to see what it would do.  Turns out that turning the screw clockwise slows down the second shutter.  Having adjusted the screw about 1.5 turns, the camera is now able to open the aperture under all conditions.  I am not sure how that affects the other shutter speeds, though it seems to work okay based on the couple of shots I took (maybe underexposing a tad, which does not actually make much sense.  Must be the lighting conditions I used.).  Now, to be clear, I may have lowered the shutter speeds of the camera at all settings.  The problem is that the fastest shutter speed of the camera is 1/1200 sec, which is too fast for me to ascertain.  Nevertheless, a little exposure compensation will presumably go a long way towards fixing that.

 

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