Evening star. [volume] (Washington, D.C.) 1854-1972, 1900-01-20
largements are made by the utilization OF
this principle.
Mag nfhes With Low Power Lens.

oS"iHes Win Low ROVER Lens.
From this explanation 1T will be plain to
All possessing even slight knowledge OF
photography that pictures showing high
magnihcation OF minute objects can be
readily taken with lens Of comparatiyely
low power. The chief difference between
protective Photography and ordinary en-
Idrsement work is this: In the latter the
enlarged negative or print is produced nv
passing the light rays through a glass posi-
. - or negative exactly as they are passed
thLoush the slide in magic lantern and
thrown up on a sensitive plate or s,nsi-
lHeu paper, while IN protective photogra-
phS the image OF the object To be pho
tosraphed Is itself thrown up''
III the object be Transparent. as n saction
OF the pla mater-the covering OF the brstn
or otner transparent tissue the light may
De passed through 1t to show its struc-
the night is allowed TO fall upon n eYactIv
as IN ordinary photography. The form 81
camera used virtually differs from Tho ar
uihary camera, only in being deeper, so
the lens ''u II 'ti
objects of much greater size may be mag
,iiii.'l photoGraphically by protective than
- ,tiicrosSopic photography. A protective
photograph" magnifying 300 times has been
taken OF the toes OF a mouse in which
every detail. even 10 the structure of each
i hair' rs clearly shown. The field of the
Iens with which the mousa's toes u.ra
taken Is almost a square inch at the close
range required, and the toes might haye
Dten enlarged COO times as readily as :no
,Iia :, MICROSCOPIC lens magnifying only -
uldiheters covers a field only one-fifth ~ A
square inch In extent. while a Ions mar
wiz magnify lWn times covers only about
l-2W Of square inch.
High and Low Power Lenses.
The accompanying diagrams will make
the difference between the high power and
the low power lens clear. FislIr. l indt-
Gates the passage of The rays from an OBJ
Ject photographed by a low power lens To-
the plate Figure shows the path Of the
rays when lens Of high power is used
The size of the object and of the irnag.. Is
assumed To be the same In both cases The
image produced by the low power glass
VIII show less detailed definition hut much
greater penetration or depth of focus while
the image thrown by the lens of bi,,b
Power Will present more details more def
milton, but less depth of focuS The mag
hllSihs lens gets the details at the expense
OF depth or perspective. while the other
lens. htted in deeper camera. allowing
greater distance between lens and plate
VIII produce equal magnification. while the
image Will possess the plastic uualifv
so called, in much greater degree. ana
therefore will Resemble the object far more
closely.
To explain a little further; Sunnosa n
round body. pearl. for instance is To br
photographed. Figure ; shows how m.
light rays would pass from the object TO
the plate through A low power lens Only
small portion of the pearl would be shown
IN the hgure-about Ii dcgreeS-but it would
appear as curved surface. though with
comparatively few details Figure shows
the path of the light rays through a high
power lens. In the figure about lnn do
SreeS are taken in. but only a very small
part of the pearl would bo photographed
though every minut"st spcck and flaw
would be clearly apparent. and the picture
would apparently Toe Of Il perfectly fiat sur
race. II this lens Wrr ha
'aN1al point Of III" pearls surface a small
circle would show sharply: If focused on
a point further away. a ring would be de-
lined. since all the nearer and farther parts
of the pearl would he either b-fnr, or be-
mind the focal plane. and hence so blurred
AS not to be- recognizable Any one look
ing at a picture of pearl taken lay mag
nihcatlon would suppose he WAS looking at
the pictur" of ring. and the true appear
ance of the object would be entirely lost.
An Art to study
The microscopical photograph is of use
only in studying surfaces, the pores Of the
skin, for instance. or any object that has
no thickness. This will be plain from the
statement that a lens magnifying loo
times has a depth Of focus of only
1-25oths of an inch. 1t will therefore show
an almost unappreciable amount of per
Spective. This is why insects when viewed
under microscope look like Silhouatfas
Insects should be studied microscopicaIIv
II proper perception of their true appear
ance is desired by procuring camera
of extra depth and slightly stronger lens
than IL commonly used the comparatively
unskilled amateur may produce magniiied
of insects and other small OBJ
jects that will surprise him. The time of
need not necessarily be great. On
u good bright day thirty seconds is gcncr-
ally sufficient for excellent results but. of
course. individual experiment is the best
teacher. Teachers may find in protective
a long desired aid in the
teaching of natural history, physiology and
chemistry