. The book of photography; practical, theoretical and applied. i 22 i 1-2 ill. 4 S 12 1(1 20 24 28 1 32 30 40 15 ill. 0 12 IH 24 30 3(5 42 1 48 54 00 IS in. 9 IS 27 3(1 4o .?)4 63 ! 72 81 90- 24 in. IG 32 48 (i4 HO 90 112 128 144 160 To use the above table, the exposure mustbe ascertained at the given distance, say18 in. Suppose this to be 72 table at once indicates how muchnearer the light the frame must be placedto bring the exposure within more reason-able limits. On a large run, this method 224 THE BOOK OF PHOTOGRAPHY. will save a considerable amount of example, at 6 i
. The book of photography; practical, theoretical and applied. i 22 i 1-2 ill. 4 S 12 1(1 20 24 28 1 32 30 40 15 ill. 0 12 IH 24 30 3(5 42 1 48 54 00 IS in. 9 IS 27 3(1 4o .?)4 63 ! 72 81 90- 24 in. IG 32 48 (i4 HO 90 112 128 144 160 To use the above table, the exposure mustbe ascertained at the given distance, say18 in. Suppose this to be 72 table at once indicates how muchnearer the light the frame must be placedto bring the exposure within more reason-able limits. On a large run, this method 224 THE BOOK OF PHOTOGRAPHY. will save a considerable amount of example, at 6 in. it will only requirean exposure of eight seconds. It mayhappen, however, that this is too near thelight to give even illumination, for theframe should never be placed at a distanceless than the diagonal of the negativebeing printed from. Duration of Exposure. A print from an average negative, uponElliotts Platino - Matt bromide paper,which is a very suitable one for a beginner,should have an exposure of about sixseconds ; using a No. 5 Brays gas Fig. 327.—Sectional Exposuke. This is merely intended as a roughguide ; the exact exposure being onlyfound by experiment. The best plan isto make an exposure in three sections,behind the negative, giving each one twicethe exposure of the preceding one; orassuming first an exposure as correct, andgiving that to the centre portion, withhalf that and double that to the outsideparts. This may be effected without anyspecial frame, by just covering up partsof the negative with a card, and givingthe assumed exposure to the first third,half this to the second third, and the sameto the la^^t third. For example, supposea negative is to be tested ; fill in paperand cover up two-thirds, as in Fig. assume any exposure to be correct,say six seconds. Give this exposure, thenturn off the light or shut off with shutter,and move the card, as shown in Fig. 329,giving half the assumed exposure, or threeseconds ; then shut off light on
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