Amateur Photographer & Cinematographer (1933)

November ist, 1933 The AMATEUR PHOTOGRAPHER p 6 CINEMATOGRAPHER a \ elective ^ Focussing Enlarging in By R. LLUELLYN. MOST methods of introducing diffusion in enlarging suffer from a common defect, namely : that the diffusion of definition is uniform. To secure diffusion of part of a picture only while another part remains sharp is the object of the following method. In the example chosen the definition of the negative used was bitingly clear, so every bit of the crepe hair in the beard (the portrait is of a stage " character ”) stood out as a separate fibre, also the texture of the coat was very marked and distracting. Any attempt to soften this by bolting silk or the usual methods produced merely an all-over fuzzy result. The following plan was therefore tried : A cardboard holder was employed, a book-form arrangement with an opening, rather smaller than the paper in use, cut out of the hinged front part so as to form a frame. This holder was laid on the easel of a vertical enlarger and the image focussed on the white surface of the back half. Now, if on the top of this a piece of ground glass, rough side down, had been laid before exposure, diffusion would of course have resulted, in consequence of the ground surface being separated from the bromide paper „by the thickness of the frame. If the ground "surface had been in contact with the paper, the image, though perhaps slightly granular, would still have been sharp. Obviously, then, what was needed was to bring paper and glass into ’contact where critical definition was wanted, * and to leave them apart where diffusion was required. All that was necessary for this purpose was to “ pack ” the framed bromide paper at the required point, much as an etching plate is packed where emphasis is desired. In practice, a slip of cardboard is placed under that area of the paper to be emphasised — in this case the eyes — and that is all ! The arrangement is shown in the diagram in vertical section, but much exaggerated for clearness. The maximum amount of diffusion will depend upon the thickness of the frame ; if this is insufficient, it can be increased by strips of cardboard, which need not extend over the whole frame, A . Back of frame. B.B. Hinged front of frame. C.C. Sup¬ ports of ground glass. D. Ground glass. E.E. Bromide paper. F. Backing slip. Enlargement made with selective focussing. as the}' serve only to support the glass. The elasticity of even heavy bromide paper is quite enough to allow of very considerable differences in level without cockling. In the present case, where only slight diffusion was required, the frame was no more than i/6th-in. thick for a 10x8 print. The packing slip was very slightly thicker so as to make sure of good contact with the glass. Placing it in position was, of course, quite easy, as it needed only to be laid on the eyes as projected. Final focussing was done on the surface of the packing slip (which for that reason was white), the bromide paper laid in position over the packing slip, the frame closed, the glass laid on it and the exposure made. In the stereotyped phrase, it was much easier to do than to describe. In the case of a landscape, with a clearly defined foreground and without a foreground object, such as a tree projecting into the sky portion, the same plan can be applied, with the result that the foreground can remain clear and sharp while the middle distance and distance are progressively diffused. This method is particularly useful for enlargements from negatives made with the modern miniature camera, in which all planes are rendered with equal sharpness. negative. 400 1 1