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The Barnet Book of Photography A Collection of Practical Articles

The interposition of a small meniscus or plano convex lens


[Illustration:

Fig. 3.]

[Illustration: Fig. 4.]

The second method of enlarging by daylight is by employing an ordinary enlarging camera. The same conditions as to lighting, etc., should be sought for, and the most convenient way of working will be to tilt the camera at such an angle as that the negative receives unobstructed illumination from the sky. A reflector in this case will not be necessary, but a piece of very finely ground glass should be placed about an inch in front of the negative in order to soften and diffuse the light. This method of working is shown in Fig. 4.

ENLARGING BY ARTIFICIAL LIGHT.

Before describing the actual process of making an enlargement it will be well to deal with the alternative method of working, namely, by artificial light, as the manipulations of the sensitive material used are the same in either case. Practically the most satisfactory way of working by the latter method is to use an enlarging lantern properly fitted with a condenser. The general principles of such an apparatus are identical with those which obtain in an ordinary optical lantern. Methods which dispense with the use of a condenser are more or less unsatisfactory, and should be avoided. In the space at the disposal of the writer it is not possible to give directions for the construction of an enlarging lantern, but those who may desire to make their own,

will find full instructions and working drawings in "[6]Practical Enlarging."

[6] A Iliffe & Son.

[Illustration: Fig. 5.]

Enlarging lanterns of excellent quality are obtainable commercially, but for the guidance of the uninitiated it may be useful to refer a little in detail to one or two important points with regard to their construction. The condenser will first claim attention. The ordinary pattern consists of two plano-convex lenses mounted as shown in section at Fig. 5. This answers fairly well with the smaller sizes, but when the diameter of the condenser is large, a good deal of light may be lost. The interposition of a small meniscus or plano-convex lens, in the manner first suggested by the late J. Traill Taylor, and shown in Fig. 6, will be found a great improvement. Its proper position will be at the point where the divergent cone of rays proceeding from it just covers the large condenser. In our own practice we always place a diffusing screen of very finely-ground glass in front of the condenser at EE The diameter of the condenser is governed by the size of the negatives to be enlarged, it must be of sufficient size to include the longer sides of the plate within its circumference without cutting the corners. If it is much larger than this, an unnecessary loss of light will occur, because only that which passes through the negative can be utilized.

[Illustration: Fig. 6.]

THE ILLUMINANT.

The smaller and more intense the light, the nearer we approach to the ideal projection illuminant, and the better will be the definition of our enlargements. The arc light most nearly fulfils the desired conditions, and if it be available it should certainly be employed. Next in point of utility comes the limelight, preferably in the form of the mixed jet, and those who understand its manipulation are recommended to adopt it, but the majority of amateurs will probably find it more convenient to use either incandescent gaslight or an oil-lamp. Parallel wick-lamps should be avoided on account of the unequal illumination they produce, and if oil must be used a good circular wick burner will be found more suitable. Where house-gas is available the incandescent gaslight is however much to be preferred. The light is perhaps not so powerful as that given by a really good parallel wick-lamp, but it is far more actinic and penetrating. The writer has used this light with great satisfaction, and therefore has no hesitation in recommending it. Some workers have been troubled by the appearance of an image of the mantle on the screen, but this can usually be got rid of by a suitable adjustment of the lenses and the light, and in any case by the interposition of a piece of ground glass between condenser and negative.


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