Page:Popular Science Monthly Volume 89.djvu/475

 Pnpiihir Science Monthly

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���When the plunger is pressed the action opens the shutter, and when the plunger is re- leased blade returns to its former position

Home-Made Camera Shutter

A SHUTTER, which is suitable for a small hand-camera, can be made from odds and ends, and occupies a space 23^"xiK"xK'"- The blade, A, is made of thin hard brass, painted dead black, loosely pivoted at the center by a small screw.

It is ij/g" in diameter, and it has a circular opening, B, for the exposure, %" in diameter. A narrow piece is removed at C, the corners coming into contact with the stop, D, consisting of a small screw. A lever, E, is pivoted to the circular blade at one end and to a second lever, F, at the other, the fulcrum of the latter being a screw, G. The shutter is operated by pressing the little plunger, //, and re- mains open until the plunger is released, when the spring, J, returns the blade to its former position.

A Useful Trimming Board

A USEFUL cutting board for trimming photographic prints can be made from a scissors blade and a few odds and ends. The illustration shows the trim- mer complete. The board is i}4" thick and of any convenient area, with part of a flat rule B screwed along the top edge. A strip of steel is screwed along the right hand side, flush with the sur- face. An old scissors blade is secured by means of a screw which forms a pivot

��or fulcrum, the necessary hole having been drill- ed through the end of the blade. It will be seen that the end of the blade has bcenground blunt and the cutting edge straight. When cutting, the blade should be pressed towards

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��The complete trim- ming board for pho- tographic prints made from a scissors blade

the Steel strip.

��Simple Test of Shutter Speed

THE following method of testing the speed of a camera shutter may be of interest to photographers who possess a bicycle. Invert the bicycle upon a suit- able support in bright sunshine, and glue a small square of tinfoil to the side rim of one of the wheels. Set up the camera in a convenient position and focus this wheel sharply. Then open the dia- phragm to its largest stop and set the shutter at its lowest speed. The wheel must be revolved at the rate of one revo- lution per second and a shutter exposure should be made while it revolves at that speed.

The wheel should then be brought to rest and a time exposure given on a second plate. This constitutes a check in the alleged speed of a shutter.

���Using a bicycle, set upside down, to measure shutter speed

A test can be made several times, and the final results carefully compared and noted. It is necessar\- in all cases to make two exposures to determine the shutter speed. The method is sufficiently accurate for all ordinary purposes and with a pair of dividers to measure the width of the image, there is little oppor- tunity to error.

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