DISTANCE FROM CAMERA.
At first thought it might appear that the farther the object is from the the greater the exposure required, but in actual practice the reverse is found to be the case, for the particles of matter sus pended in the air cause the light to be independently reflected, and throw a luminous veil between the image and the camera, allowing a shorter exposure by the flattening influence it exerts upon the contrast. Again, an object at a con siderable distance from the lens receives, generally speaking, the unobstructed light from the sun, and is therefore capable of reflecting a full quantity. It only needs to take an exposure including some near fore ground objects and some distant objects, especially if the latter consists of sea and sky, to see how greatly the required ex posures will differ. Roughly, about sixteen times the exposure will be required for the near view with shadows in the foreground as is required for sea or sky, supposing light, stop, plates, etc., are the same in
each case.
These tables—also the work of Prof. ri Scott—were compiled for use with the Ilford exposure meter, and are reproduced by kind permission of Ilford, Ltd. It will ?be noted that the tables for northern ;latitudes read June to December, whilst 'those for southern latitudes read Decem ber to June, December in these countries being the summer month.
Loss OF ULTRA VIOLET RAYS.
Even when the glass of the lens is not tinted, there may be a decided loss of ultra violet rays. With glass (such as is used usually in making lenses) half an inch thickness permits only 55 per cent. of the ultra violet rays to pass. Seeing, however, that in this country the ultra violet rays arc, as a rule, generally extracted before