The outfit of the retoucher should also include a good lens, and in order to avoid the fatigue resulting from the unequal use of the eyes with ordinary lenses, we cannot too strongly recom mend the use of binocular lenses making use of both eyes ; these lenses are generally fixed to the head by means of a ribbon, or by side pieces as in the case of spectacles, thus leaving both hands free.
475. Technique of Retouching. Work with the scraper should always precede that with the pencil' and it must nut be lost sight of that the retoucher should always restrict his work to what is absolutely necessary, being guided by a good print from the negative.' The scraper is used by its point or its edge, according to the extent of the marks which have to be erased or the outlines to be modified ; it must be handled very lightly in the same way that it would be used to remove an ink mark on paper ; avoid any heavy cuts which would pierce the gelatine. It must always be remem bered that the pencil must be used on the scraped parts in order to finish the work and to equalize the density on the scraped parts with those of the surrounding areas.
Before proceeding to retouch with the pencil it will be necessary to cover the portions to be worked on with a very light coat of medium.' For this purpose, a very small wad of cotton wrapped neatly in linen is used with a drop of the medium on it, or the end of the finger may be used. The excess may be removed by rubbing with the palm of the hand.
For preference, the hardest pencil capable or giving the desired effect will be used ; thus the B pencil will be kept for those parts of which the density is to be considerably increased. The pencil should be applied very lightly in dots of fine hatching, straight or curved, or in over lapping circles. Each mark should be so light as to be hardly visible by itself ; the direction of the marks should follow the general lines of the subject. Fig. 177 shows on an enlarged scale some of the styles commonly adopted for re touching. The pencil should always be applied
very lightly, the pressure being slightly greater in the middle of each mark than at the extremi ties. If it is required to darken certain parts of the image considerably, they must be worked over several times, each time putting on the marks at 45° to their preceding direction. Any retouching work which is too heavy may be lessened by scraping ; moreover, at any time work may be entirely removed with a little turpentine or matolin.
During the process of retouching, it is well to examine the negative from time to time by turning it gelatine side downwards on the desk in order to judge the effect better.
Parts which are not dark enough, due to insufficient pencil work, may also be treated by stippling them with a fine brush moistened with crimson lake (water-colour).
After the retouching has been finished a trial print is made and is carefully compared with the original print.
476. Added Backgrounds. Some photo graphers occasionally pose their models in front of a black background, filling in a background to the negative by subsequent work on the glass side. One of the methods used for this purpose is very old (La Blanchere, 1863), and has even been used by some celebrated painters to make " negative drawings " of pictures and so to furnish an infinite number of prints by means of photographic printing. The negative (or plain glass) is placed on a black ground (velvet, cloth, paper) and the desired design is drawn on the glass by painting with white body-colour ; it thus appears as a positive by reflection and a negative by transmitted light.
For very simple backgrounds (draperies, clouds, etc.), a very light and uniform layer of finely-powdered red chalk may also be deposited on the glass ; this is worked on by wiping off with a cloth or stump. In this way only very feeble contrasts can be obtained, but the effect may be very agreeable. The work is protected by spraying a fixative or by covering with another glass.