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so lets say i take a small lcd, and stick a lens in front of it. a magnified image will be projected on a wall. now lets remove this wall and stick a camera a little behind where the image is formed (so the projected image is supposed to fill the whole field of view of our camera). the image doesnt fill up the cameras sensor. instead, the camera only sees the magnified part of the object only inside the first lens thats far away. the camera still sees everything around this lens.

now if ive placed a real object where the supposed projected image is supposed to be, then that does fill up my cameras entire field of view.

ive drawn an image. according to the ray diagrams, i expected to have this image fill up the camera sensor. this is not my result.

diagram

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  • $\begingroup$ Your camera can only "see" the rays that hit its lens. Look at the three blue rays that you drew from the LED to the real image. If you extend those rays, they don't go anywhere near the camera's lens. $\endgroup$
    – Solomon Slow
    Apr 21, 2018 at 14:40
  • $\begingroup$ I get that, but ive been reading about 2 lens systems, and it is said that the projected image from the first lens then becomes the new object for the second lens, so tracing the ray diagram from the new object like in the image I posted I thought would form the image on the lens. $\endgroup$
    – tyroneb
    Apr 21, 2018 at 15:05

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Although your diagram is not to scale a slight addition to your diagram will perhaps answer your question?

enter image description here

I have drawn the cone of rays which emanate from the top of your object (blue) and those from the bottom of the object (green).

You will note that none of those rays pass through the camera lens and so no image will be formed of the top or bottom of your projected image.

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A simplified diagram below shows that the camera field of view of the object (LCD in your example), outlined by red lines, is limited to the size of the first lens, L1, i.e., the camera cannot "see" anything outside the diameter of that lens.

enter image description here

If we wanted to increase the camera field of view of the object so that it matches the field of view of the camera or "fills up" the sensor (as shown in purple), we would have to increase the size of the lens to L2, accordingly.

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  • $\begingroup$ Awesome. This perfectly explains everything for me. Thank you. $\endgroup$
    – tyroneb
    Apr 21, 2018 at 16:53

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