why is it in both these cases (zoomed in and zoomed out background), the "distance from the subject increases to maintain its size"? what does it mean to increase with focal length? it's also very interesting that as the focal length increases, we zoom into the background, but the human subject looks more balanced as if the image plane is perfectly vertical. however, with the decreased focal length, the subject is less balanced; it seems that their body, hands, and facial features are larger, making the proportions seem off. i believe that this may be because these components, especially the body and hands, are closer to the camera, meaning that they are larger with the short focal length.
saif-m17
To answer the first part of your question, I think the diagram a few slides from now does a pretty good illustration. The way I understand it is: the idea is that with a smaller focal length, the field of view is larger/wider so you have to be closer in order for the size of the subject to be the same. With a large focal length, the field of view is less wide, so in order for those rays to intersect at the same points (since the angle is now smaller), you need to be farther back.
why is it in both these cases (zoomed in and zoomed out background), the "distance from the subject increases to maintain its size"? what does it mean to increase with focal length? it's also very interesting that as the focal length increases, we zoom into the background, but the human subject looks more balanced as if the image plane is perfectly vertical. however, with the decreased focal length, the subject is less balanced; it seems that their body, hands, and facial features are larger, making the proportions seem off. i believe that this may be because these components, especially the body and hands, are closer to the camera, meaning that they are larger with the short focal length.
To answer the first part of your question, I think the diagram a few slides from now does a pretty good illustration. The way I understand it is: the idea is that with a smaller focal length, the field of view is larger/wider so you have to be closer in order for the size of the subject to be the same. With a large focal length, the field of view is less wide, so in order for those rays to intersect at the same points (since the angle is now smaller), you need to be farther back.