Page 33 - The Wellington photographic handbook

It is sometimes asked whether a light filter can be used to
advantage with ordinary plates. It certainly slightly improves
the colour rendering, but since it cuts off most of the light except
the yellow and green, to which ordinary plates are only slightly
sensitive, it prolongs exposure to such an extent as to make its use
prohibitive. A WELLINGTON Light Filter, for example,
which with a WELLINGTON Iso-Speedy plate necessitates
only five times the exposure, with a WELLINGTON 'Xtra
Speedy might require as much as several hundred times the ex-
posure. So that a light filter can only be used to advantage with
an Iso plate.
Moreover, if the advantage is to be secured with as little
prolongation of the exposure as possible, the light filter employed
—
"
must be adjusted to the plate itself, and its strength " five times
or what not—only holds good for that particular plate. A " five
times " light filter with one plate may very well become a "ten
times " light filter with another. An Isochromatic plate will give
a better rendering with any commercial yellow colour screen than
without it, but to get that improvement without the exposure
being needlessly long, the colour screen must be adjusted to the
plate.
It is a moot point with photographers whether a light filter
should always be used with an Iso plate or not. Some say that
there is little or no advantage in using an Iso plate at all, unless
a light filter is also used. Others hold that even without a light
filter, the improvement is sufficiently marked in almost all cases to
justify the use of Iso plates. Again, personal taste must decide.
Good advice to the photographer is to start with ordinary
plates, since not being so sensitive to the light they are more easily
handled in the dark-room. Then, when he feels fairly familiar
with them, let him pass to the use of Iso plates and of the light
filter, and decide for himself whether the more faithful colour
rendering pleases him better.
There can be no question about the alteration when the light
filter is employed ; but in many cases it lengthens the exposure
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