SCREEN-PLATE COLOUR PHOTOMICROGRAPHY 



213 



All the screen plates have the disadvantage of a grain 

 of the coloured elements over the surface, which prevents 

 the reproduction of fine detail, and may on close inspec- 

 tion or projection be troublesome. 



The Duf ay and Paget plates give positives that are con- 

 siderably more transparent than the Autochrome, and can 

 be projected more easily in a lantern. It is also possible 

 to wash the emulsion from spoilt plates of these makes, 

 leaving a serviceable screen for the duplicating process. 



The screen plates require rather long exposures, which 

 in certain cases is a drawback. Messrs. Lumiere now 

 make a special sensitising bath by which the speed of 

 their plates can be increased 4 or 5 times, and supply a 

 screen suitable for use with the extra-sensitised plates. 



