. The book of photography; practical, theoretical and applied. ount of silver from all the differ-ent gradations of the negative. Fig. 219is intended to represent the various de-grees of light and shade in a negativewhich is slightly too dense all over. As amatter of fact, this is a condition whichrarely obtains, the lights always fendingto be denser in proportion than theshadows ; but the example will serve forthe purposes of illustration. The action ofsuch a reducer, then, should be equal on allparts of the negative, producing the resultshown by Fig. 220, where the portions 142 THE BOOK OF P
. The book of photography; practical, theoretical and applied. ount of silver from all the differ-ent gradations of the negative. Fig. 219is intended to represent the various de-grees of light and shade in a negativewhich is slightly too dense all over. As amatter of fact, this is a condition whichrarely obtains, the lights always fendingto be denser in proportion than theshadows ; but the example will serve forthe purposes of illustration. The action ofsuch a reducer, then, should be equal on allparts of the negative, producing the resultshown by Fig. 220, where the portions 142 THE BOOK OF PHOTOGRAPHY. removed are indicated by dotted lines. Itwill be interesting, therefore, to comparethe action of two reducing agents of oppo-site properties in the same manner. Action of Ferricyanide and Per-sulphate Compared. The ferricyanide reducer and ammoniumpersulphate are chosen for the purpose ofthis comparison, as presenting the mostinstructive differences. A negative ofgreater contrast than Fig. 219 will be moresuitable, such as that shown by Fig. 221,—Negative of Steep Gradation. As already noted, the ferricyanide reducerattacks the shadows in greater degree thanthe lights. The result is shown in Fig. 222,where the contrast of the negative has sim-ply been increased, although the generaldensity has been reduced. It is thisproperty of attacking the shadows mostwhich makes the ferricyanide reducer ofgreat value for the improvement of nega-tives which are both dense and lacking in 1 W/i/M 1 » WM///, \/////////////// //////////////////// nniiinnniniiinniniiiiiDDnmin/niiiiiiiDiiim))/////////////// mmm 222.—Action op Feebicyanide Eeducek. contrast. Ammonium persulphate, on theother hand, has a directly opposite reduces the lights or denser parts ofthe negative much more than the shadows,having a flattening effect on the contrast(see Fig. 223). It should therefore be usedfor hard, chalky negatives, and in any casewhere the light and shade require soften-ing
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