The American annual of photography . i ins. 216 Precisely the same method may be employed in we have a lens with the node marked, and wish touse it on an enlarger. Having screwed it on the front ofthe latter, we rack the front in or out until the distance fromthe negative to the node is exactly equal to the focal length, asin Figure 4. To do this, we must place a negative in thecarrier, and with a piece of card ascertain carefully how farthe gelatine surface is from the edge of the frame. This isthen marked outside the carrier. Next, by measuring- fromthe mark to the outer si
The American annual of photography . i ins. 216 Precisely the same method may be employed in we have a lens with the node marked, and wish touse it on an enlarger. Having screwed it on the front ofthe latter, we rack the front in or out until the distance fromthe negative to the node is exactly equal to the focal length, asin Figure 4. To do this, we must place a negative in thecarrier, and with a piece of card ascertain carefully how farthe gelatine surface is from the edge of the frame. This isthen marked outside the carrier. Next, by measuring- fromthe mark to the outer side of the lens-board, and from that. /KONT rose --9/4-. ^ew OH p,^^^ Figure 3. ~ 2 - ^ NOOF TO • to the nodal mark on the lens, it is quite easy with a few ad-justments to get the latter at its principal focus from thenegative. Now, without moving the front, indicate the posi-tion of the fixed base-board of the enlarger by a mark onthe sliding extension frame carrying the lens, as shown bythe arrow. Having done this, we have the same state ofthings as originally existed with the camera. If, for in-stance, we make a second mark on the sliding extension frameone-fourth of the focal length behind the first mark, andmove the extension frame forward till the mark corresponds 217 with the edge of the base-board, the apparatus is accuratelyfocused for a four-diameter enlargement, and one need onlymove the easel, without any other adjustment, till the imageis seen to be sharply focused. A scale, also, may be pre-pared and fixed to the extension frame for obtaining enlarge-ments to any other desired size, and this scale will ha
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyorktennantandw
