humanfaculty4 - page 263 of 305

Composite Portraiture

order of exposure. Let us call the four component wafers A, B, C, D, respectively, and the

four composite wafers 1, 2, 3, 4 then we see, by the diagram, that the order of exposure

has differed in each case.

Successive places of the Components.

yet the result is identical. Therefore the order of exposure has no effect on the result.

I will next show a series consisting of two portraits considerably unlike to one another,

and yet not so very discordant as to refuse to conform, and of two intermediate

composites. In making one of the composites I gave two-thirds of the total time of

exposure to the first portrait, and one-third to the second portrait. In making the other

composite, I did the converse. It will be seen how good is the result in both cases, and how

the likeness of the longest exposed portrait always predominates.

The next is a series of four composites. The first consists of 57 hospital patients

suffering under one or other of the many forms of consumption. I may say that, with the

aid of Dr. Mahomed, I am endeavouring to utilise this process to elicit the physiognomy of

disease. The composite I now show is what I call a hotch-pot composite; its use is to form

a standard whence deviations towards any particular sub-type may be conveniently

gauged. It will be observed that the face is strongly marked, and that it - is quite idealised.

I claim for composite portraiture, that it affords a method of obtaining pictorial averages,

which effects simultaneously for every point in a picture what a method of numerical

averages would do for each point in the picture separately. It gives, in short, the average

tint of every unit of area in the picture, measured from the fiducial lines as co-ordinates.

Now every statistician knows, by experience, that numerical averages usually begin to

agree pretty fairly when we deal with even twenty or thirty cases. Therefore we should