SCIENCE- GOSSIP. 



TILE PIIOTOGKAIMIY OF COLOUR. 



"By E. Sanger Shepherd* 



THE term "photography of colour'' is a wide 

 one, and in this article I propose to deal 

 with only two of its many branches, (a) the photo- 

 graphy of a coloured object in its natural colours, 

 and (I) the representation of a coloured object in 

 a monochromatic print — work somewhat unhappily 



sent the lights and shades of the object photo- 

 graphed as seen by the normal human eye. For 

 instance, blues apparently dark to the eye 

 photograph as white, and bright yellows are repre- 

 sented in the print as black. The object of ortho- 

 chromatic photography is to obtain in a moim- 



Itvv i.s a.ULe 

 UUra.Vi.olet: 



Violet 



Gveeu 



YelLc 



Orzuiqe 



RecL 



Fig. 3. 



Fie. 1. SrECTiiu.M of White Light (Solar Spectrum'*, Pig. 2. Visual Luminosity of Spectrum (expressed by a curve). 

 Fig. 3. Spectrum Sensitiveness of an Obdixary Dkyplate. 



known as orthochromatic or isochromatic photo- 

 graphy. 



The second of these divisions, the representation 

 of a coloured object in a monochromatic print, is 

 perhaps the more simple problem of the two,' and 

 may be dealt with first with advantage. 



It is well known that when we photograph 

 brightly coloured objects upon the ordinary photo- 

 graphic dry -plate or film, our print does not repre- 

 A.UG. 1900.— No. 75, Vol. VII. 



chrome print a rendering of all colours more in 

 accordance with the visual impression. 



Let us think for one moment of what we are 

 trying to do. It is obvious that in photographing 

 a coloured object we have two scales of contrast — 

 firstly, " contrasts of colour," and, secondly, " con- 

 tacts of light aud shade," but obviously we cannot 

 represent contrasts of colour in black and white, so 

 that our inquiry is really narrowed down to obtain- 



i) 



