Page 493 
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6. Focal-plane shutters, because of 
their higher efficiency, need only one- 
half the exposure which is required 
when using a between-the-lens shutter. 
The correct exposure may be arrived 
at by various methods 
1. Experience. 
The experienced 
photographer 
knows with a fair 
degree of accuracy 
what exposures to 
give under most 
conditions. He may 
seem to arrive at 
his exposure by in¬ 
tuition, but as a 
matter of fact his 
decision, though 
apparently made 
instantly, is made 
with a full knowl¬ 
edge of the factors 
involved, and with 
previous successes 
and failures in 
mind. This method 
is the only prac¬ 
tical one in speed 
work with the re¬ 
flex where no time 
can be given to cal¬ 
culating exposures. 
It is, however of 
little use in photo¬ 
graphing insects, 
plants, and other 
subjects at very 
close range. 
2. Exposure 
tables. There are 
many sets of ex¬ 
posure tables avail¬ 
able, and while 
they are an aid to 
an understanding 
of the matter of 
exposure they are 
not so well adapted 
to the needs of the 
wild life photo¬ 
grapher as calcu¬ 
lators or meters. 
3. Exposure 
calculators. These 
indicate the expo¬ 
sure by correlating the factors in a 
mechanical manner. Several types can 
be obtained, one of the most efficient 
being the Wellcome. 
4. Exposure Meters. Meters are of 
two types: 
A. Those which measure the light in¬ 
tensity by means of sensitive paper 
and correlate this with the stop and 
plate speed by the turning of a dial. 
They are very efficient instruments. 
Reliable meters of this type are the 
Wynne and the Watkins. 
IN NATURE'S GARDEN—LADY SLIPPER, A WOODLAND CLASSIC 
Heyde Aktinophotometer is a good 
meter of this type. 
While it is important for the nature 
photographer to know the correct ex¬ 
posure it is not by any means always 
the case that he can give this expo¬ 
sure, because many exposures are 
bound to be a compromise between full 
exposure and the maximum exposure 
which can be given without danger of 
blur due to the movement of the sub¬ 
ject. Wild life photography, especially 
pictures of birds and mammals, often 
4 t r a y s a little 
larger than the 
plates used. 
2 large trays 
(each holding 4 
plates laid flat). 
1 plate-washer. 
1 plate drying 
rack. 
1 centigrade chem¬ 
ical thermo m- 
eter. 
1 balance, prefer¬ 
ably with metric 
weights and 
weighing at least 
to decigrammes. 
1 250 cc. gradu¬ 
ate. 
A supply of the 
following chem¬ 
icals : Sodium 
thiosu1p h a t e 
(Hypo), An¬ 
hydrous Sodium 
sulphite, Anhy¬ 
drous Sodium 
carbonate, An¬ 
hydrous Sodium 
bisulphite, Po¬ 
tassium bromide, 
Chrome alum 
(powdered), Hy- 
droquinone, Me- 
tol (or Mono- 
met, or Elon). 
The balance, 
thermometer and 
graduate may be 
obtained from any 
dealer in scientific 
apparatus. 
The most satis¬ 
factory method of 
development is the 
Time and Temper¬ 
ature System, be¬ 
cause it eliminates all guesswork and 
yields the best negative which can be 
obtained from every exposure. It is 
the only system that can be used with 
panchromatic plates. 
A table of temperatures and their 
corresponding times can be constructed, 
by careful experimental work (for di¬ 
rections see The Dictionary of Photog¬ 
raphy, by E. J. Wall, p. 216), for any 
developer. The following developer is 
thoroughly satisfactory: 
(Continued on page 510) 
B. Those which measure the light 
intensity optically by means of a ro¬ 
tating wedge of colored glass, and in¬ 
dicate the exposure on a dial by means 
of a pointer moving with the glass 
wedge. These instruments are accu¬ 
rate and quick in operation. The 
calls for three things which unfortu¬ 
nately are incompatible—depth of field, 
quick shutter-speeds, and full exposure 
and a large part of the art of the sport 
lies in balancing these three factors so 
as to obtain the best possible negative 
under the conditions presented. 
The equipment 
needed for devel- 
