DOI Page / Citation link:
https://doi.org/10.11588/diglit.62828#0360
There is a certain diftance fhorter than which the eye can-
not eaiily fee a picture; and therefore if an object be delineated
by fuch a diftance, it will appear unnatural.
In Plate XIV. Fig. i, let BD be the length of the picture,
and Z the place of the fpedator’s eye, and e the center of the
pidt ire, then will Z e be the diftance of the picture; but as Z e
is very little more than half the length of the picture B D,
therefore the angle under which the whole picture would be
feen at Z, is almoft ninety degrees.
This is an angle which the eye cannot eaiily take in, be-
caufe the ray Z B is in a hate too diverging to the pupil of the
eye, and therefore the fpedator muff twift and ftrain his eye,
before he could fee the whole extent B D.
The optical reafon of this is as follows:
Produce the vifual rays LP, K P. Now, it is evident, from
the fcale on the arch, that thefe rays fubtend an angle of more
than ninety degrees. Therefore iince, according to optical laws,
rays will not unite in a point on the retina at a greater obliquity
than an angle of forty-five degrees, confequently the points K L
will not appear to the eye. This is probable enough from the
figure
not eaiily fee a picture; and therefore if an object be delineated
by fuch a diftance, it will appear unnatural.
In Plate XIV. Fig. i, let BD be the length of the picture,
and Z the place of the fpedator’s eye, and e the center of the
pidt ire, then will Z e be the diftance of the picture; but as Z e
is very little more than half the length of the picture B D,
therefore the angle under which the whole picture would be
feen at Z, is almoft ninety degrees.
This is an angle which the eye cannot eaiily take in, be-
caufe the ray Z B is in a hate too diverging to the pupil of the
eye, and therefore the fpedator muff twift and ftrain his eye,
before he could fee the whole extent B D.
The optical reafon of this is as follows:
Produce the vifual rays LP, K P. Now, it is evident, from
the fcale on the arch, that thefe rays fubtend an angle of more
than ninety degrees. Therefore iince, according to optical laws,
rays will not unite in a point on the retina at a greater obliquity
than an angle of forty-five degrees, confequently the points K L
will not appear to the eye. This is probable enough from the
figure