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التصوير الفوتوغرافي الحديث
التقاط الصور في 3 - د
عرض صور الاستريو، النظر من خلال العارض،
إسقاط شرائح ستيريو
VIEWING STEREO PICTURES
When you look at anything normally , your eyes do two things : they focus on the object , as does a camera lens , and they swing inward or converge , so each eye looks directly at the object . The eyes are parallel , or nearly parallel only when at rest or when viewing the most distant objects . Under normal circumstances they toe in or converge just the right amount to permit both eyes to look at the same spot on the object .
This convergence of the eyes is one of the important elements in enabling us to judge distance . Without this toeing in of the eyes , you would have difficulty telling whether you are looking at a small object close - up or a large object farther away . It accounts for the ability of people who have lost the sight of one eye to judge distance with a surprising degree of accuracy , even though they no longer have binocular vision . The remaining eye retains its ability to toe in , and thus continues to judge distance reasonably well .
LOOKING THROUGH THE VIEWER
When you look at stereo pictures through a viewer , you are not looking at these pictures in the normal manner . Your eyes focus on the actual slide in the viewer , but they converge on the apparent distance of the subject you have photographed . Bear in mind that this convergence is a necessary element in re - creating the effect of distance .
At your first viewing of stereo slides , your eyes not accustomed to focusing for one distance and converging for another . You may , therefore , have a little difficulty in seeing depth at first . However , the eyes soon accommodate themselves to this unusual situation if you adjust the focus and lens separation of the viewer for most comfortable use .
PROJECTING STEREO SLIDES
The essential condition for stereo viewing that each eye sees only its own picture . Because of this it is necessary , when projecting stereo slides , to do it in such a way that the left eye , for example , can see only the left picture of the stereo pair , and the right eye can see only the right picture . This can be done with the aid of polarized light .
Light , as you know , is a form of wave motion . When light is emitted by any source such as a lamp filament , it vibrates in all directions - vertically , horizontally , and all angles in between . It is possible to produce certain types of filters ( called polarizing filters ) which act somewhat like grates and pass only the light which vibrates in the same direction , or plane , as the grating .
You can demonstrate the polarization of light very easily . Obtain two pieces of polarizing film - two Polaroid filters or two pairs of Polaroid glasses . Hold one of the filters before your eyes and look at any bright object . The only effect as far as you can tell is some loss of light . Actually , however , the light you now see is polarized light , vibrating in one direction only . Now take the second filter and hold it in front of the first . Rotate it slowly while you look through both filters . At a certain angle , the light will be completely shut off . In this position , the two filters are at right angles to each other . The polarized light passed by the first filter is vibrating at right angles to the plane of polarization of the second filter , and so whatever light passes the first is blocked by the second . This is illustrated in Figure 5 .
The principle of polarization is used in the projection and viewing of stereo slides . Suppose we take a stereo slide and project it onto a screen with a suitably designed twin lens projector , one lens for each image , so that the two images are slightly separated on the screen . You would merely see a double image . Now let us place separate polarizing filters over each lens . We adjust the filters so that one ( let us assume it is the left eye image ) is polarized vertically . We then adjust the other filter so that the right eye image is polarized horizontally .
Figure 5 Polarizing filters act as grates to passage of light . First filter passes only light which is vibrating in same direction as its plane of polarization . If second filter is turned at right angle to first filter , it will block all light passed by first filter .
We will still see both images because both eyes can see polarized light . However , if we place a vertically polarized filter in front of the left eye , that eye will see only the left eye image because it is also polarized vertically . No light from the right eye image , which is polarized horizontally , can reach the left eye . If we place another filter in front of the right eye and rotate it until its polarizing axis is horizontal , the right eye will see only the right eye image .
We have here the necessary condition for true binocular vision - each eye sees only one slightly different image . The brain merges the two images and we see a natural three - dimensional picture .
There are , of course , many practical considerations in successful three - dimensional projection . The polarizing filters are usually set so the axis of one is 45 ° to the left of vertical , and the axis of the other is 45 ° to the right of vertical . The projection screen must have a metallic surface , since metal does not change the axis of polarization of light reflected from it as do non - metallic screens . The viewing filters are made up as inexpensive viewing glasses . ( Note : Polaroid sunglasses cannot be used for stereo viewing , since both filters in the sunglasses are set to give the same angle of polarization . )
To get the correct three - dimensional effect , the separation of the two projected images must be related to the screen size and the distance at which the screen is viewed . This relation imposes some limitations , but projectors are made so they can be adjusted as necessary for the most effective viewing .
التقاط الصور في 3 - د
عرض صور الاستريو، النظر من خلال العارض،
إسقاط شرائح ستيريو
VIEWING STEREO PICTURES
When you look at anything normally , your eyes do two things : they focus on the object , as does a camera lens , and they swing inward or converge , so each eye looks directly at the object . The eyes are parallel , or nearly parallel only when at rest or when viewing the most distant objects . Under normal circumstances they toe in or converge just the right amount to permit both eyes to look at the same spot on the object .
This convergence of the eyes is one of the important elements in enabling us to judge distance . Without this toeing in of the eyes , you would have difficulty telling whether you are looking at a small object close - up or a large object farther away . It accounts for the ability of people who have lost the sight of one eye to judge distance with a surprising degree of accuracy , even though they no longer have binocular vision . The remaining eye retains its ability to toe in , and thus continues to judge distance reasonably well .
LOOKING THROUGH THE VIEWER
When you look at stereo pictures through a viewer , you are not looking at these pictures in the normal manner . Your eyes focus on the actual slide in the viewer , but they converge on the apparent distance of the subject you have photographed . Bear in mind that this convergence is a necessary element in re - creating the effect of distance .
At your first viewing of stereo slides , your eyes not accustomed to focusing for one distance and converging for another . You may , therefore , have a little difficulty in seeing depth at first . However , the eyes soon accommodate themselves to this unusual situation if you adjust the focus and lens separation of the viewer for most comfortable use .
PROJECTING STEREO SLIDES
The essential condition for stereo viewing that each eye sees only its own picture . Because of this it is necessary , when projecting stereo slides , to do it in such a way that the left eye , for example , can see only the left picture of the stereo pair , and the right eye can see only the right picture . This can be done with the aid of polarized light .
Light , as you know , is a form of wave motion . When light is emitted by any source such as a lamp filament , it vibrates in all directions - vertically , horizontally , and all angles in between . It is possible to produce certain types of filters ( called polarizing filters ) which act somewhat like grates and pass only the light which vibrates in the same direction , or plane , as the grating .
You can demonstrate the polarization of light very easily . Obtain two pieces of polarizing film - two Polaroid filters or two pairs of Polaroid glasses . Hold one of the filters before your eyes and look at any bright object . The only effect as far as you can tell is some loss of light . Actually , however , the light you now see is polarized light , vibrating in one direction only . Now take the second filter and hold it in front of the first . Rotate it slowly while you look through both filters . At a certain angle , the light will be completely shut off . In this position , the two filters are at right angles to each other . The polarized light passed by the first filter is vibrating at right angles to the plane of polarization of the second filter , and so whatever light passes the first is blocked by the second . This is illustrated in Figure 5 .
The principle of polarization is used in the projection and viewing of stereo slides . Suppose we take a stereo slide and project it onto a screen with a suitably designed twin lens projector , one lens for each image , so that the two images are slightly separated on the screen . You would merely see a double image . Now let us place separate polarizing filters over each lens . We adjust the filters so that one ( let us assume it is the left eye image ) is polarized vertically . We then adjust the other filter so that the right eye image is polarized horizontally .
Figure 5 Polarizing filters act as grates to passage of light . First filter passes only light which is vibrating in same direction as its plane of polarization . If second filter is turned at right angle to first filter , it will block all light passed by first filter .
We will still see both images because both eyes can see polarized light . However , if we place a vertically polarized filter in front of the left eye , that eye will see only the left eye image because it is also polarized vertically . No light from the right eye image , which is polarized horizontally , can reach the left eye . If we place another filter in front of the right eye and rotate it until its polarizing axis is horizontal , the right eye will see only the right eye image .
We have here the necessary condition for true binocular vision - each eye sees only one slightly different image . The brain merges the two images and we see a natural three - dimensional picture .
There are , of course , many practical considerations in successful three - dimensional projection . The polarizing filters are usually set so the axis of one is 45 ° to the left of vertical , and the axis of the other is 45 ° to the right of vertical . The projection screen must have a metallic surface , since metal does not change the axis of polarization of light reflected from it as do non - metallic screens . The viewing filters are made up as inexpensive viewing glasses . ( Note : Polaroid sunglasses cannot be used for stereo viewing , since both filters in the sunglasses are set to give the same angle of polarization . )
To get the correct three - dimensional effect , the separation of the two projected images must be related to the screen size and the distance at which the screen is viewed . This relation imposes some limitations , but projectors are made so they can be adjusted as necessary for the most effective viewing .
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