Le 8.9.2002 4:21, « Gregory Fraser » <Gregory.Fraser@pwgsc.gc.ca> a écrit : > Pardon my interruption but I think what Dave is talking about is compression > as opposed to perspective. The vertical and horizontal placement of objects > does not change from one focal length to another however the relative size of > objects does change with focal length as does the apparent depth of the image. > Doesn't it to you? Not exactly, the point is that the relative sizes of objects don't change : in Dave's example, on the first picture, the distance from photographer to the first object is 100 feet and the distance between the two objects is 10 feet; in his second picture, the difference from photographer to the first object is 10 feet and the distance between the two objects is 1 feet. So in Dave's example itself, only the absolute distances have changed, not their relative locations. Now, Dave also said : > ... They now look a lot closer to you and > much closer to each other which is also as it should look because the 500mm > lens on a 35mm SLR gives a ten X scope effect. The signs look about ten > feet away and one foot apart. He said that they "look" and this is the crucial word : they look so, because they now fill the frame, but they aren't so.. If one were doing the math (anyone ?) the distance would be the same in both case. The result is a magnification but not a change in space or in perspective. One thing more, in Dave's example, the second sign appears smaller than the first one. A change in space (a move of the photographer) and the second sign could appear to be of the same size, or even bigger, but without moving the photographer can't alter the relative size of the two signs.
