STEREOGRAPHIC TECHNIQUE 99It is not advisable to carry the use of these masks to the extreme.
A set of four or five negative window masks may be used nor-
mally, but the fancy shapes should be reserved as a kind of spice
Fig. 6-1. Masks (A). There is little value in a mask when the back-
ground of the picture and the mask haue similar tonal values. The
shape of the mask is lost. (The flower is a night-blooming cereus.)
Fig. 6-2. Masks (B). Fancy shapes may be used, but they are rarely
successful unless given a conspicuous position. This one places the
window in the plane of the stamen.
to the collection, and used sparingly to preserve the novelty ap-
peal (Figs. 6-2, 6-3 and 6-4).
FILING AND STORAGE.-Any collection of stereograms rapidly
grows to such an extent that no hit-or-miss filing system (or lack