For work abroad where extremes of temperature or excessive variations have to be contended with, a special tropical camera is supplied by most of the leading makers.  Its well-seasoned hard wood and metal-bound joints render it suitable for hard wear, and reduce the risk of leakage through warping or shrinkage.  The tripod stand should be of the so-called threefold variety, with sliding legs which can be adapted to broken ground.  If a loose screw is used for attaching the camera to the stand, a spare screw should be kept in reserve.  It is important that this stand should be strongly made, and light patterns subject to undue vibrations in the wind should be discarded.  For photographing small objects in the studio, a small table is more convenient than a tripod support.  If the camera will not sit flat on the table, a bed can easily be designed for it.  Better work will be done if this is prepared in advance than if an improvised support is used.  As regards the size of the outfit, quarter-plate (3 1/4 x 4 1/4 inches) will usually be found to be large enough for the traveller.  For anything in the nature of studio work in a museum or in connexion with an excavation a half-plate camera (6 1/2 x 4 3/4 inches) is more satisfactory.  Where a hand camera is preferred it should be one capable of adjustment of focus, and here again, strength and simplicity should be looked for.  It should be provided with effective tripod legs, for studied exposures.  Plates or flat films are preferable to roll fills [2] which are difficult to manipulate away from home.  Flat films are less bulky and less breakable than glass, and can be sent by post.  They are supplied by the makers in packs of 12 for daylight loading into a film-pack adapter, which must be provided to take the place of the ordinary dark slides for glass plates.  The lens should be a modern anastigmatic by a good maker.  A focal length of about six inches will be best for a quarter-plate camera.  A bad lens makes success impossible even by accident.

[2] Transcriber’s note:  ‘fills’ in the original text is possibly a misprint for ‘films’.

The stops will probably be of the Iris pattern, incorporated in the lens and so not likely to be lost, as often happens with loose stops.

A few words on the theory and use of the stops and on the F-notation may be of service.  The speed of a photographic lens depends on the ratio of the effective aperture to the focal length.  Thus any two lenses used at apertures of F/8, that is at apertures having diameters one-eighth of their respective focal lengths, should be of the same speed, though both lenses and apertures may be very different.  In a given lens, the speed varies directly with the area of the aperture admitting the light, that is with the square of the diameter of the aperture.  The series of stops usually employed is calculated so that each aperture is half the area of the preceding.  Stated in terms of the focal length they are known as F/5.6,