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when the two portraits are taken on a quarter plate is and 
when done on a half-plate they may be -J the natural size 
To get this reduction the chair for the sitter should have 
a perfectly vertical back, and the seat should be 25 cm. 
square. On the seat place an upright of any kind of 
sufficient length that it may be seen conveniently through 
the camera. The surface of the upright facing the camera 
should be 19 cm. in front of the back of the chair for the 
full-face portrait, and 5 cm. nearer the camera than the 
centre of the back of the chair in the profile portrait. Paste 
or fix to the upright a strip of newspaper 28 cm. long, 
move the camera backwards or forwards till the image of 
the paper when focussed on the screen measures exactly 
4 cm. long. This will be a reduction to the natural size 
of the object. To get a reduction of focus a strip 30 cm. 
long so that it shows, when focussed on the screen, a length 
of 5 cm. Having fixed the distance of the camera from the 
chair, mark the exact positions of each so that at any time 
they may be replaced. When the native takes his seat on 
the chair, he will be in focus and his image on the screen 
reduced to the proper amount. Fine focussing should be 
done on the outer angle of the left eye in the full face and 
the coresponding point of the right eye in profile, but this 
is seldom required if care is taken to see that he sits upright. 
To determine whether the sitter is in full face, direct him 
to look at the lens and see that his ears project on the focus¬ 
sing screw exactly to the same extent from on each side of 
his head. It will assist very much in getting the true profile 
if a mirror be hung up with its surface exactly parallel to a line 
from the centre of the chair to the centre of the lens, by ad¬ 
justing his head till his ears appear exactly the same size in 
the mirror, his profile will then be at right angles to the 
camera, the centre of the mirror should be 4 feet from the 
ground, and should have a spot marked on it for the sitter to 
look at. As a tripod camera-stand will have generally to be 
used, it is well to be able to raise and lower to a given height. 
This can be done by attaching to a ring three strings or wires 
of exactly the same length, then having got the proper spread 
R 2 
