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Ram Nanda

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About Ram Nanda

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  • Birthday 10/12/1994

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  • Occupation
    Student
  • Location
    Chennai, India

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  1. @Kyryll Sobolev : thank you for the explanation😃
  2. @AJ Youngyes. what you said is right and practical. @Gregory Irwin good motto by the way 😅
  3. Mr. Michael Rodin, Mr. AJ Young & Mr. Gregory Irwin, I texted Mr.Joy Holben, who the original article in AC mag, regarding the very same question I raised in the initial post. (find the conversation in the comments section of : https://ascmag.com/blog/shot-craft/the-entrance-pupil-of-the-lens) Here he accepts that the while Depth of Field covers up the minor difference in the planes between Entrance Pupil and Image/film/sensor plane but it is in the case of macro work this fails. It's in these situations eye focus is required than measurement from sensor plane. So like Mr.AJ Young said, in 99% cases its from the Φ (film/sensor/image plane) we measure focus. So in these 99 cases entrance pupil = film/sensor/image plane. and in one case entrance pupil ≠ image plane. RIGHT ? Correct me if i'm wrong. I know we don't often come across this in reality, but I'm just curious in knowing this stuff. And if anyone can, please provide reference website/pdf/book. Thanks, Ram Nanda
  4. Thank you Mr. Gregory. putting aside the technical difficulties related to measuring focus from entrance pupil, why is entrance pupil the right position for focus calibration ?
  5. on larger depth of field the difference between entrance pupil plane and image plane is negligible and is covered by depth of field. but its clearly evident at extreme small DoF, like in the case of macro close ups where you have to judge by eye
  6. According to AC Magazine April 2020 edition " The Pupil Marks the Focus Spot The next thing to understand about the entrance pupil is that it is at that point — not at the film plane (or sensor plane) — from which focus should be measured. It’s a long-standing practice in cinematography to take focus measurements from the film or sensor plane of the camera. " (read the attachment) Well, the topic seems to be fine and interesting but, the basic question is never raised nor answered - WHY FOCUS SHOULD BE MEASURED FROM ENTRANCE PUPIL? Can some one explain these : 1) Do all of the points of light from the scene converge to a single point at the entrance pupil and then expand back out to the image plane ? 2) What role does exit pupil play in measuring focus ? 3) Can Iris be located not at aperture stop ? 4) How is DoF related to entrance & exit pupil ? And please provide a reference website or material to understand these technical concepts clearly. Thanks, Ram Nanda.
  7. According to AC Magazine April 2020 edition " The Pupil Marks the Focus Spot The next thing to understand about the entrance pupil is that it is at that point — not at the film plane (or sensor plane) — from which focus should be measured. It’s a long-standing practice in cinematography to take focus measurements from the film or sensor plane of the camera. " (read the attachment) Well, the topic seems to be fine and interesting but, the basic question is never raised nor answered - WHY FOCUS SHOULD BE MEASURED FROM ENTRANCE PUPIL? Can some one explain these : 1) Do all of the points of light from the scene converge to a single point at the entrance pupil and then expand back out to the image plane ? 2) What role does exit pupil play in measuring focus ? 3) Can Iris be located not at aperture stop ? 4) How is DoF related to entrance & exit pupil ? And please provide a reference website or material to understand these technical concepts clearly. Thanks, Ram Nanda.
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