Evening star., 1951-06-03


the jargon of the trade that some
times We are apt to forget the be-
ginner may become bewildered by
some of the terms and phrases that
we so casually use during the
course of an article. In Difference
to these embryo camera fans we
present another section of our
glossary of Photographic termi-
nology.
A large bellows extension is Of
ten needed when making copies or
when shooting extreme close-upS
to produce an image of desired
size. In such a case the bellows
factor" must be taken into con-
sideration when computing the ex-
posure. An increase in exposure
is called for because the increase
of the distance between the film
and lens reduces the image bright
ness for. given aperture. To de-
termine the bellows factor, meas
ure the distance from the lens dia-
phragm to the film and divide this
figure by the focal length OF the
lens-then square the result. The
correct exposure may then be easily
determined by multiplying your
meter indicated exposure by this
factor.
All cameras, by the way. do not
have a bellows" This is a square
shaped tapering accordion-llKe
connection between the lens and
the back of the camera which Is
light tight and permits the
photographer to change the dis
tance from the lens to the film to
focus the image correctly. II your
camera has a bellows it should be
kept free of all dust or grit in the
folds. Otherwise abrasive action OF
this material will eventually wear
holes in the bellows, allow lgnt
to leak into the camera ana your
films will be ruined.
Use of Safelights.
A darkroom" is a light-eight
room, where the cameraman de-
velops his Aim and prints. 1t IS
usually furnished with "satel
light" which permits the handing
of sensitized material without the
danger of Jogging. The rays OF
the safelight, if used within pre-
scribed limits, will not affect
Photographic papers. A red safe
light may be used for brief IN
spections of orthochromatic films,
but should not be left on under
any circumstances when panchro-
matte film is unprotected. Any
room may be used as darkroom
If all outside light is excluded.
The diaphragm" or stop" OF
a lens is a device usually found
between the elements Of the lens
which admits light through the
center of the lens while cutting
off the marginal rays OF light. In
some cameras the device will be
found in front of the lens, while
in others it is placed behind the
lens. Most cameras in the medium
price field have an iris" dla-
phragm. This consists OF series
of thin overlapping metal leaves
which are operated by manual
control to vary the size OF the
opening and regulate the amount
of light passing through the lens.
You will notice that the lens
housing will have a series of cali
brations. These will regulate the
exact amount of light that will
be admitted through the lens at
a given setting. Such numbers as
f:8. fill, etc., will be noted.
It is important to know that in
changing the aperture from one of
these numbers to the next num-
Der will either double or halve
the exposure at given shutter
speed. depending upon whether
the aperture is opened or closed.
For example, if you are shooting
at a constant speed of 1/100th of
a second and make one exposure
with a diaphragm setting Of f:S
you will cut that exposure in half
by stopping the aperture down to
3:11. The advantage of using the
aperture control is apparent when
you consider that shutter speeds
vary from the indicated rating.
Haze Filters.
When shooting aerial pictures
or distant landscapes you will
often encounter a condition known
as aerial haze. The unaided lens
will not penetrate this haze anc
the "haze filter" is applied ovel
the lens to allow it to see through
and record scenes that would 9th
erwise appear dim and cloudy Fol
ordinary purposes an orange G
filter will prove satisfactory with
black-and- white film. A special
haze filter is required for color
film.
A film hanger" is a rectangu-
lar metal or plastic frame which
is used to hold cut film while il
is being processed through the de-
veloper, short stop, fixing bath
and washing and drying phases o.
the operation. Projecting edge
of the upper section of the hanger
rest on the edges of the tanks ane
allow the film to remain suspend
ed in the solutions. Roll films arr
usually processed in a film tank
which is fitted with a reel upor
which the film is wound. Thi
type film tank is light-tight ant
the film is processed in the single
vessel, one solution at time be-
.rg poured in through a baff1et
opening and then poured of again
after serving its purpose,
"ens Sap' is a snug-f1ttnl
cover made of plastic, metal O.
leather, which should always b.
placed over the lens Of your cam
era when it is not in use. Th'
lens cap will protect the mos
valuable part of your camera from
scratches, dust and dirt. But b.
sure to remove it before you com
mence shooting pictures; other
wise voll'll get blanks.