204 Botanical Microtechnique 



Attachment Cameras 



In view oi the iact that most photomicrography is done with a 

 standard microscope used in conjunction with some form of accessory 

 camera, this type of apparatus will be discussed first. A highly satis- 

 factory type of attachment camera consists of a lightweight metal 

 camera which is fastened to the ocular tube and is carried by the 

 microscope tube without additional support. The microscope may 

 be used for visual study in its normal position, and, when a field 

 of view is to be photographed, the camera can be placed into position 

 without disturbing the microscope. These cameras do not have a 

 bellows or an extendable body and the projection distance therefore 

 is fixed. Magnification is varied by changing objectives and oculars. 

 The largest camera of this type takes negatives 9 by 12 cm., or 31/4 by 

 41/^ in. The projection distance is such that the magnification factor 

 is IX- Therefore, the image magnification is equal to the product 

 of objective and ocular magnifications. Smaller models take negatives 

 414 by 6 cm., 6.5 by 9 cm., and 35 mm. respectively, and have a 

 lower magnification ratio, in accordance with the shorter projection 

 distance. 



Focusing is accomplished in some models by an observation lube 

 having either a telescopic ocular or a ground-glass screen. A prism 

 within the camera diverts all or part of the image-forming rays into 

 the observation tube. When the image is in focus in the observation 

 tid)e or screen, it also is in focus in the plane of the negative. The 

 eyepiece observation tid^e may not give precise focus with objectives 

 of less than lOX. in which case the ground-glass screen in the plane 

 of the cnuilsion nuist be used. 



The camera fastens to the microscope by a clamping collar. A 

 fixed ocular tube gives greater rigidity than a drawlube, unless the 

 diawtiibc lias a positive locking device. A further aid to rigidity con- 

 sists of a biass sleeve pressed around the upper end of the ocular 

 liil)c and tinned on a lathe luitil the slee^•e makes a tight fit into 

 the (lamp (ollar of the camera. The camera can be re\()l\cd to orient 

 the image — thus a revolving stage is not necessary. 



Exam))les of such cameras are the Zeiss I'liokii. the Leit/ Makani, 

 and the Erb and Gray Visicam (Fig. 17.1) . 



In the Zeiss and Leitz, the e\pensi\e local plane shutter, range 

 finder and other devices are a total waste if the camera is to be used 

 oidy foi photomicrography. Ihe Visicam and Histoslide use a simj)le 

 35-nmi. canieia body, the sole f miction ol which is to hold the spool 

 of film. 



