. The microscope; a simple handbook. Microscopes. 74 THE MICROSCOPE Vertical photo- micro- graphio camera. tte stage of tte instrument, and tlie slide of the plate-holder is drawn. The exposure may now be made by withdrawing the card, replacing it and closing the plate-holder. The use of colour screens (see page 42) is of great service in_ photography to increase contrasts, but the student is referred to books on this subject for detailed information as to photo- graphing difficult objects. At the same time, the photography of most microscopic objects is so simple that the ordinary observer ne
. The microscope; a simple handbook. Microscopes. 74 THE MICROSCOPE Vertical photo- micro- graphio camera. tte stage of tte instrument, and tlie slide of the plate-holder is drawn. The exposure may now be made by withdrawing the card, replacing it and closing the plate-holder. The use of colour screens (see page 42) is of great service in_ photography to increase contrasts, but the student is referred to books on this subject for detailed information as to photo- graphing difficult objects. At the same time, the photography of most microscopic objects is so simple that the ordinary observer need not be deterred by the complexity of the instruction given for the most advanced work. There are two general forms of photomicro- graphic cameras. One is vertical and is used with the microscope in a ver- tical position. The other requires the microscope to be placed in a hori- zontal position, and con- sists of a metal bar on raising and lowering screws which carries a camera with a variable extension adjusted by means of bellows. The vertical camera consists of a frame stand- ing on three strong legs splayed out to give sta- bility. It has a slide FiQ. 86.—No. 3342, Vertical Photomioro- on its upper surface into graphic Camera. which either a ground glass screen or a double plate-holder is inserted. Below this frame is a flexible bag which fits over the upper end of the drawtube of the microscope and can be attached by a cord. The size of plate used is 4J X 3J- inches (quarter-plate), and the distance from the upper end of the standard microscope is such that, with the 30-mm. compen- sating eyepiece, it gives a circular picture of about 3 inches. It is rigid, and Ught, and extremely convenient. When the micro- scope is adjusted with all the care required to obtain the best image the camera is placed over it, attached to the tube by means of the bag, and a touch of the fine adjustment is aU that is neces- sary. In order to focus the imageon the ground glass accurately,. P
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