May 23, 1878] 



NATURE 



97 



COMPOSITE PORTRAITS^ 



T SUBMIT to the Anthropological Institute my first 

 ^ results in carrying out a process that I suggested last 

 August in my Presidential Address to the Anthropolo- 

 gical Subsection of the British Association at Plymouth, 

 in the following words : — 



" Having obtained drawings or photographs of several 

 persons alike in most respects, but differing in minor de- 

 tails, what sure method is there of extracting the typical 

 characteristics from them? I may mention a plan which 

 had occurred both to Mr. Herbert Spencer and myself, the 

 principle of which is to superimpose optically the various 

 drawings and to accept the aggregate result. Mr. Spencer 

 suggested to me in conversation that the drawings reduced 

 to the same scale might be traced on separate pieces of 

 transparent paper and secured one upon another, and 

 then held between the eye and the light. I have at- 

 tempted this with some success. My own idea was to 

 throw faint images of the several portraits, in succession, 

 upon the same sensitised photographic plate. I may add 

 that it is perfectly easy to superimpose optically two por- 

 traits by means of a stereoscope, and that a person who 

 is used to handle instruments will find a common double 

 eyeglass fitted with stereoscopic lenses to be almost as 

 effectual and far handier than the boxes sold in shops." 



Mr. Spencer, as he informed me, had actually devised 

 an instrument many years ago, for tracing mechanically, 

 longitudinal, transverse, and horizontal sections of heads 

 on transparent paper, intending to superimpose them and 

 to obtain an average result by transmitted light. 



Since my Address was published, I have caused trials 

 to be made, and have found as a matter of fact that the 

 photographic process of which I there spoke, enables 

 us to obtain with mechanical precision a generalised 

 picture ; one that represents no man in particular, but 

 portrays an imaginary figure, possessing the average 

 features of any given group of men. These ideal faces 

 have a surprising air of reality. Nobody who glanced at 

 one of them for the first time, would doubt its being the 

 likeness of a living person. Yet, as I have said, it is 

 no such thing ; it is the portrait of a type, and not of an 

 individual. 



I begin by collecting photographs of the persons with 

 whom I propose to deal. They must be similar in atti- 

 tude and size, but no exactness is necessary in either of 

 these respects. Then by a simple contrivance I make 

 two pin-holes in each of them, to enable me to hang 

 them up one in front of the other, like a pack of cards, 

 upon the same pair of pins, in such a way that the eyes 

 of all the portraits shall be as nearly as possible super- 

 imposed ; in which case the remainder of the features 

 will also be superimposed nearly enough. These pin- 

 holes correspond to what are technically known to printers 

 as "register marks." They are easily made ; a slip of 

 brass or card has an aperture cut out of its middle, and 



threads are stretched from opposite sides, making a cross. 

 Two small holes are drilled in the plate, one on either 



* Made by combinina: those of many different persons into a single re- 

 sultant figure. By Francis Galton, F.R.S. Paper read before the Anthro- 

 pological Institute, April 30. . . 



side of the aperture. The slip of brass is laid on the 

 portrait with the aperture over its face. It is turned 

 about until one of the cross threads cuts the pupils of 

 both the eyes, and it is further adjusted until the other 

 thread divides the interval between the pupils in two 

 equal parts. Then it is held firmly, and a prick is made 

 through each of the holes. The portraits being thus 

 arranged, a photographic camera is directed upon them. 

 Suppose there are eight portraits in the pack, and that 

 under existing circumstances it would require an exposure 

 of eighty seconds to give an exact photographic copy of 

 any one of them. The general principle of proceeding is 

 this, subject in practice to some variation of details, de- 

 pending on the different brightness of the several portraits. 

 We throw the image of each of the eight portraits in turn 

 upon the same part of the sensitised plate for ten seconds. 

 Thus, portrait No. i is in the front of the pack ; we take 



the cap off the object-glass of the camera for ten seconds, 

 and afterwards replace it. We then remove No. i from 

 the pins, and No. 2 appears in the front ; we take off the 

 cap a second time for ten seconds, and again replace it. 

 Next we remove No. 2, and No. 3 appears in the front, 

 which we treat as its predecessors, and so we go on to the 

 last of the pack. The sensitised plate will now have had 

 its total exposure of eighty seconds ; it is then developed, 

 and the print taken from it is the generalised picture of 

 which I speak. It is a composite of eight component 

 portraits. Those of its outlines are sharpest and darkest 

 that are common to the largest number of the com- 

 ponents ; the purely individual peculiarities leave little 

 or no visible trace. The latter being necessarily dis- 

 posed equally on both sides of the average, the outline 

 of the composite is the average of all the components. 

 It is a band, and not a fine line, because the outlines of 

 the components are seldom exactly superimposed. The 

 band will be darkest in its middle whenever the com- 

 ponent portraits have the same general type of features, 

 and its breadth or amount of blur will measure the ten- 

 dency of the components to deviate from the common 

 type. This is so for the very same reason that the shot- 

 marks on a target are more thickly disposed near the 

 bulls-eye than away from it, and in a greater degree as the 

 marksmen are more skilful. All that has been said of 

 the outlines is equally true as regards the shadows ; the 

 result being that the composite represents an averaged 

 figure, whose lineaments have been softly drawn. The 

 eyes come out with appropriate distinctness, owing to 

 the mechanical conditions under which the components 

 were hung. 



A composite portrait "represents the picture that would 

 rise before the mind's eye of a man who had the gift of 

 pictorial imagination in an exalted degree. But the 

 imaginative power even of the highest artists is far from 

 precise, and is so apt to be biased by special cases that 

 may have struck their fancies, that no two artists agree 

 in any of their typical forms. The merit of the photo- 

 graphic composite is its mechanical precision, being sub- 

 ject to no errors beyond those incidental to all photo- 

 graphic productions. 



I submit several composites made for me by Mr. H. 

 Reynolds. The first set of portraits are those of criminals 

 convicted of murder, manslaughter, or robbery accom- 

 panied with violence. It will be observed that the 

 features of the composites are much better looking than 

 those of the components. The special villainous irregu- 



