e. You can use a polarizing screen to reduce annoying reflections in
scenes that include water, glass, or other shiny surfaces. Look through the
polarizing screen while rotating it to see how you can control the
reflections when you are shooting through a car window, shop window, or
water. As you've read before, getting the maximum effect with a polarizing
screen depends on your angle to the subject as well as the rotation of the
If you can't remove the reflection completely, try changing your
angle to the subject. Don't expect to control reflections from bare metal
surfaces, because the light reflected from these surfaces is not polarized
and the screen will have no effect.
f. One last trick with a polarizing screen.
If you combine a red
filter, no. 25 or no. 29, with a polarizing screen and photograph a clear,
sunny scene with blue sky and no clouds, you can obtain a good simulation of
a moonlit night. This is admittedly a rather special effect, but it's fun
to try and sometimes will produce a surprisingly effective picture.
Learning Event 7:
USE A COMBINATION OF FILTERS
Don't forget that when you combine a neutral density filter or
polarizer with another filter, you must multiply the filter factors together
and then adjust your exposure according to this combined filter factor. It
isn't so easy when you combine two colored filters.
a. For example, if you were to combine a red and green filter (for some
unfathomable reason) you couldn't simply add the factors.
The red filter
will have already eliminated almost all the green light and the green filter
will eliminate almost all the red light. The combination of the two filters
blocks out nearly all light, and the resulting exposure adjustment may be
ten stops or more. (Ten stops is a filter factor of 1024, by the way.) This
is an extreme example, but the principle still holds for lighter colored
b. If you decide to use two filters in combination, hold the pair over
the sensor of your meter and note how much the meter changes.
This is a
"quick and dirty" way of getting an estimate of what the combined factors
are. Then, after you have seen the results in the developed negative, make
a note of whether you got a good exposure or not, and adjust accordingly.
At first glance, holding the filter over the meter sensor would seem to be a
reliable way of finding a filter factor. But in some cases, especially with
strongly colored filters, you can get misleading results.
sensitivity of some meter cells differs markedly from the sensitivity of
Red filters are notorious for this, because some older
meter sensors are highly sensitive to red - much more so than film.
meter responds strongly to light through the red filter and indicates a high
exposure value. But the film, less sensitive to red, will be underexposed.
Don't let this throw you. Using the meter to estimate a filter factor is
usually reliable; but not always.