Page Two
THE MICHIGAN DAILY
-
Friday, October 22, 1971
U-
IN FOCUS
Fine points of filters
Al
.t
coming . . . for HALLOWEEN
sensational
black & white
.--3D--
I
spectacular
COLOR
by Richard Lee
Q. What are the most useful
filters? - Steve T.
A. Depends on what your ob-
jective is.
It might be simpler if this
column first attempts to explain
abot light and filters in gen-
gral.
When white light falls on an
object, the object first changes
the structure of the light by
absorbing all colors but its own,
and then reflects back its own
color. Subtraction is the key.
A red apple, for example, re-
flects back red, therefore by
subtraction blue and green are
absorbed.
Breaking white light into its
three primary colors of red, blue,
and green, the yellow that the
eye perceives is usually formed
by a combination of red and
green light. For example, a yel-
CORRECTION
In Tuesday morning's paper,
The Daily reported that tic-
kets for the homecoming con-
certs were sold out. This is not
true, and tickets are still on
sale in the Union and at Sal-
vation records. The Daily re-
grets the error.
low flower reflects back red and
green, but absorbs blue.
Filters operate in a very sim-
ilar fashion.
The color of the glass indi-
cates which colors pass through
to the film. And the principle of
subtraction indicates w h i c h
colorsare partially or totally
held; back.
A simple rule to remember is
that filters transmit (or pass)
their own color, absorb (or hold
back) part or all of other colors.
A RED filter transmits red,
but absorbs blue and green.
A GREEN filter transmits
green,.but absorbs red and blue.
A YELLOW filter (red p u s
green) transmits red and green,
but absorbs blue.
The strength of the filter in-
dicates how much of a particular
color or set of colors is absorbed.
There are two main reasons
for the use of color filters for
black and white filming.
One of them is to correct the
imperfect color sensitivity of the
film, and make it translate the
subject into tones of gray of
more or less the same bright-
ness as the colors appears to the
eyes. Such filters are called cor-
rection filters .
The other reason is to distort
(brighten or darken) the repro-
duction of certain colors for
special effects by using filters of
deeper colors than for tonal cor-
rection.
Nearly all the black and white
film generally used is panchro-
matic innature indicating that
the. film is sensitive to all visi-
ble light, as well as to invisible
ultra-violet radiation.
The human brain perceives a
yellowish-green color as t h e
greatest visual stimulation in
daylight. Pan film, on the other
hand, is comparatively more sen-
sitive in the blue-violet region.
Hence, a yelow filter that will
absorb blue, but transmit the
red and ,green of the spectrum
will be the filter to use for cor-
recting colors to their p r o p e r
gray scale tonal relationship.
This is true only of outdoor
scenes though, because then the
source of illumination, usually
the sun, is white light.
.When you shoot indoors, the
source of illumination is in all
probability a tungsten light
bulb, which emits a much warm-
er light than the midday sun.
The correction filter here is a
light green filter.
Apart from acting as a cor-
rection filter for proper gray
tonal reproduction of outdoor
scenes, a yellow filter is most
often used because it absorbs
the blue of the sky, darkening
it, thereby causing a greater se-
paration of the white clouds,
while still retaining the proper
tone of faces.
For a stronger effect, a deeper
yellow or orange filter has to
be used. This of course, should
be used only for special effects
as it distorts face tone, render-
ing it chalky white. Using a red
filter would make the sky ap-
pear almost black, but face tone
would be washed out, almost
pale. Red lips in this case would
be deathly white/ Most undesir-
able, if the scene includes peo-
ple, but for a stunning pictorial
landscape, the red filter is very
essential. Combined with a pol-
arzing filter, you might e v e n
create a prize winning landscape
photo.
Using a filter requires an in-
crease in exposure time or f-
stop. If you have a built in
through the lens light meter, the
exposure correction will be tak-
en care of automatically, in
most cases.
If you're using a separate hand
held exposure meter, you'll have
to adjust for the filter being
used.
All filters have a filter factor
engraved on the rim. This fac-
tor is usually expressed as 2x,
3x, or whatever-x. A 2x factor
means you divide your film's
ASA number, for example Tri-X
at 400, by 2. The quotient is 200.
This number then is the ASA
you get when using Tri-X rated
normally with a 2x filter. So
you now set your hand held me-
ter to read exposures with a ASA
film rating of 200.
As previously noted, do not do
this if your meter is a through
the lens type. Just set it at the
regular ASA 400, or whatever
the film's normal rating is, and
the meter will automatically
compensate for the reduced
amount of light reaching it af-
ter passing through the filter.
Q. How about a UV or Sky-
light filter for use with black
and white as well as color film?
A. Most photographers look
upon these type of filters as a
cheap way of protecting their
precious and expensive lenses
from getting dusty, and heavens
forbid, scratched!
Because a UV or Skylight fil-
ter is colorless, it requires no
increase in exposure - o n c e
screwed into the lens, you can
practically forget its presence
and sleep more peacefully.
Q. What's the difference be-
tween a UV and a Skylight fil-
ter?
A. Both absorb ultra-violet
radiation but the skylight filter
will also absorb a bit of the blue
and green while the UV filter
will only absorb the blue with
little effect on the green.
Both filters are recommended
when shooting color portraits in
open shade, and the use of
either filter will add warmth to
the scene. The UV filter, being
a very very pale yellow in color
warms the scene by throwing a
very pale yellow cast.
The Skylight filter on the
other hand is very pale pink in
color, so the very slight color
cast is pinkish.
Does that mean if you use it
with color film, people will turn
out with yellow or reddish faces?
No. Because most color films,
especially Kodak's Ektachrome
is sort of biased towards blue,
so the use of either of these
filters will just correct or add
warmth back to the scene.
Also as mentioned, light in the
open shade, in high altitudes or
snow scenes, is excessively blue,
so the use of these filters once
again just corrects for the blue-
ness.
If you shoot in normal sun-
light, it will add warmth to the
scene. Complexions will come out
looking healthy.
It is also recommended for use
with color film when shooting
with electronic flash, because
most strobe lights are cold, i.e.,
biased towards the blue. How-
ever, a few of the newer strobes
have a yellow-pink cast so as to
warm the inherently cold quality
of electronic lights. If a UV
or Skylight filter is used in com-
bination with this type of flash,
the result might be a bit warm-
er than desired. But it's all a
matter of taste.
Obviously there are more filt-
ers made than can be described
in this column; like color con-
version filter, color balancing
filters, contrast blue filters, po-
larizers, diffusers, split focus,
close-ups etc. For further in-
formation on the subject, con-
sult Kodak's "Filters for Black-
and-White and Color Pictures".
Here's some information on the
UAC sponsored Photography
Contest.
There will be two categories,
one for black and white, the
other for color. Minimum print
size is 5x7, while the maximum
size is 20x24. All prints must
be mounted.
Entries can be submitted to
the UAC office in the Union
from Nov. 8-11. Photographs
will be displayed in the Graduate
Library from Nov. 15th to Dec.
3rd.
Total prizes amounting to
$100 are being donated by UAC
and Purchase Camera Shop.
Entry forms may be picked up
from the UAC office beginning
Oct. 27th For further informa-
tion, call 763-1107.
eyes of hell
"In the gruesome division, this one is really very
good."-L.A. TIMES
fri.-sat., oct. 29-30
Natural Science Aud.
7:30-9-10:30
ARM 761-7849
G.B. SHAW
Caesar an
Cleopatra
OCTOBER 20-23; Curtain at 8 P.M.!
Box Office opens at 12:30
UNIVERSITY PLAYERS-POWER CENTER
U
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AUDITIONS
FOR ANN ARBOR CIVIC THEATER PRESENTATION
OFJ
FIDDLER ON THE ROOF
will be held from 1-5 p.m. for characters
from 7-10 p.m. for ensemblej
SUNDAY, OCT. 24-201 Mulholland Dr.
' t (Ensemble call-backs 7-10 p.m. Oct. 26)
( C(C haracter ca ll-backs 1-5 p .m . O ct. 30 )
Friday and Saturday
GRAPES OF WRATH
(1940) based on JOHN STEINBECK'S
novel, directed by JOHN FORD
with HENRY FONDA, JANE
DARWELL and JOHN CARRADINE
Merle Haggard's favorite movie
SHOWN AT 7 & 9
Aud. A, Angell Hall
x
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We Service all makes and models--Cameras and Projectors
//upot Caftin 4a en'ice, S..
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SENSES.A TURBULENT MOVIE
ONSLAUGHT!" -CUE MAGAZINE
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E
VANESSA
REDGRAVE
FINAL
DAYS
OLIVER
REED
Miss J glories in the
softness of our Lanz dress
for big doings this fall.
It's cream cotton velour
and brown cotton
suedecloth with an
embroidered midriff
between. . .very soft
and pretty. 5-13 sizes.
A'
in Ken Russell's Controversial Masterpiece
Tc~i
14 't
$38.
Y
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III
(FiF(O1'"H Forum
FIFTHAVNUE AT LIBERTY
liii pOWNTOWN ANN ABOR
LJLJ INFORMATION 761.9700
FRI. 7-9-11
SAT. 5-7-9-11
V
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