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#371
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On perspective
"mcgyverjones" wrote in message . .. "Nostrobino" wrote in message . .. "mcgyverjones" wrote in message .. . "Anthony Ralph" wrote in message ... mcgyverjones wrote: :: "Nostrobino" wrote in message :: . .. ::: [...] ::: He isn't "cropping" anything, any more than using a normal f.l. ::: lens is "cropping" what WOULD have appeared in a wide-angle shot. ::: He's using the 300mm lens because that is what gives him the ::: perspective he wants. Does this also imply a more distant camera ::: position? Obviously! :: And it's the distance that provides the perspective, not the focal :: length. Surely he is using the 300mm lens to acheive the field of view he wants. Perspective is a function of camera to object distance. Exactly. Now tell Nostrobino that (or beat your head against the wall). I am beginning seriously to doubt that half of you even know what "perspective" means. (Other than "duhhhh, something to do with camera position.") I don't see a lot of duhhh's here. But we do have a pretty fundamental disagreement on what perspective means. As far as I am concerned this feels like trying to explain that the earth orbits the sun. Perspective in a photograph is a result of camera position. That, and focal length. You cannot produce wide-angle perspective with a long-focus lens, regardless of camera position. I have said this several times already. No one has refuted it and no one can. If perspective really were only "a result of camera position" then obviously you could get any perspective you wanted simply by moving the camera around. You can't. Wide angle photographs look different than normal or tele photos, but the difference is not perspective (even though lots of people think it is and call it that). Those lots of people are perfectly correct in doing so. The difference is perspective. They can see it, I can see it, and I'll bet you could see it before you read some nonsense that told you it wasn't really there. How would you define "perspective"? Not what causes it, what IS it? What do you see in a picture that you call perspective? Answer that correctly and you have to admit that wide-angle perspective (etc.) exists. Telephoto lenses do not compress the subject, but the camera to subject distances commonly utilized in tele shots show what we call compressed perspective. The spatial compression demonstrated by long lenses results from their magnification and small angle of view. The change in apparent object relationships (position, size, angles etc.) that this produces certainly does qualify as a change in perspective. A photographer may choose a particular focal length to gain a large field of view (as in interior photography), high magnification (wildlife photography) or pleasing perspective (portrait photography). While these things are all necessarily interrelated, they are entirely different reasons for selecting focal lengths. In each case, camera position is simply what it has to be in order to get the desirted result with the lens selected. Thus you may hear a photographer say, "I like to use a 100mm lens for portraits"--rather than, for example, "I like to shoot portraits from a distance of about seven feet." He chooses the focal length for the perspective he wants, and the camera position follows from that. Not the other way around. |
#372
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"mcgyverjones" wrote in message . .. "Nostrobino" wrote in message . .. "mcgyverjones" wrote in message .. . "Anthony Ralph" wrote in message ... mcgyverjones wrote: :: "Nostrobino" wrote in message :: . .. ::: [...] ::: He isn't "cropping" anything, any more than using a normal f.l. ::: lens is "cropping" what WOULD have appeared in a wide-angle shot. ::: He's using the 300mm lens because that is what gives him the ::: perspective he wants. Does this also imply a more distant camera ::: position? Obviously! :: And it's the distance that provides the perspective, not the focal :: length. Surely he is using the 300mm lens to acheive the field of view he wants. Perspective is a function of camera to object distance. Exactly. Now tell Nostrobino that (or beat your head against the wall). I am beginning seriously to doubt that half of you even know what "perspective" means. (Other than "duhhhh, something to do with camera position.") I don't see a lot of duhhh's here. But we do have a pretty fundamental disagreement on what perspective means. As far as I am concerned this feels like trying to explain that the earth orbits the sun. Perspective in a photograph is a result of camera position. That, and focal length. You cannot produce wide-angle perspective with a long-focus lens, regardless of camera position. I have said this several times already. No one has refuted it and no one can. If perspective really were only "a result of camera position" then obviously you could get any perspective you wanted simply by moving the camera around. You can't. Wide angle photographs look different than normal or tele photos, but the difference is not perspective (even though lots of people think it is and call it that). Those lots of people are perfectly correct in doing so. The difference is perspective. They can see it, I can see it, and I'll bet you could see it before you read some nonsense that told you it wasn't really there. How would you define "perspective"? Not what causes it, what IS it? What do you see in a picture that you call perspective? Answer that correctly and you have to admit that wide-angle perspective (etc.) exists. Telephoto lenses do not compress the subject, but the camera to subject distances commonly utilized in tele shots show what we call compressed perspective. The spatial compression demonstrated by long lenses results from their magnification and small angle of view. The change in apparent object relationships (position, size, angles etc.) that this produces certainly does qualify as a change in perspective. A photographer may choose a particular focal length to gain a large field of view (as in interior photography), high magnification (wildlife photography) or pleasing perspective (portrait photography). While these things are all necessarily interrelated, they are entirely different reasons for selecting focal lengths. In each case, camera position is simply what it has to be in order to get the desirted result with the lens selected. Thus you may hear a photographer say, "I like to use a 100mm lens for portraits"--rather than, for example, "I like to shoot portraits from a distance of about seven feet." He chooses the focal length for the perspective he wants, and the camera position follows from that. Not the other way around. |
#373
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On perspective
"mcgyverjones" wrote in message . .. "Nostrobino" wrote in message ... "Jeremy Nixon" wrote in message ... Nostrobino wrote: I'm being generous. It might be called a spherical projection in the sense that, if you represent the position of the object relative to the camera in spherical polar coordinates (two angles and a distance), then the position of the image point corresponding to the object is determined by the two angles (but not the distance). But you're right, it's not really a projection of a sphere onto a flat surface, and not a spherical projection in the cartography sense. Anyway, you're still the only person in the entire world who thinks that focal length affects perspective. No, it's a common misconception. It's a common and correct perception. Actually, no, I'm far from "the only person in the entire world who thinks" that. Anyone who can see what's in front of him (and whose reasoning power has not been destroyed by reading nonsense) can see that a photo taken with a wide-angle lens has an entirely different perspective from a photo taken with a long lens from the same position. Unfortunately, you appear to be one of those so afflicted; as I recall you insisted repeatedly that there is "no such thing as a telephoto look," etc. There is a telephoto look, it is derived from the distances that telephoto photographs are commonly taken at. The telephoto look (i.e., perspective) occurs with long lenses irrespective of camera to subject distance. Do table-top photography with a long lens and you still have the telephoto look. Jeremy, the problem here is that you're trying to see the world aroundyou as the inside surface of a sphere, which it simply is not. It's a three-dimensional world, made up of three-dimensional objects, and all a rectilinear lens does is create a two-dimensional representation of those objects, whatever is in front of it that it's able to view. And how does it do that? If it's not a spherical projection, what is it? You can't just say it makes a 2D representation of a 3D world; there has to be a method of doing that. Anyway, I'm not asking you, I'm basically done with you. Go in peace then, brother, and enjoy the sphericity of your spherical world. So you really are a flat-earther? No, I'm a three-dimensionaler. So you're agreeing with Jeremy that it's all a spherical projection? Actually, this whole sphere thing (as fascinating as it may be to some) is irrelevant to perspective. You will want to talk to Jeremy about that, not me. To demonstrate how perspective can only be affected by camera position, YES! YES! That is exactly what I have been asking people here to do, and have had no takers. Just show me how you can get the same perspective with a 135mm lens (or whatever) that you do with a 28nn lens (or whatever). Use any camera position you like to do that. imagine various straight lines between the camera and subjects (fore, mid and background). These lines represents the path of the cameras line of site, or of light travelling from subject to camera. So far, so good. These lines define the subject's relationship to one another and the background. No, sorry, they do not. They define nothing but the directions from the camera to those parts of the subject(s). Of course they are not affected by focal length, Change the focal length and you get MORE such lines at wider angles, or FEWER such lines at narrower angles. The lines you had before the f.l. change are either added to, or subtracted from. Ergo, they are indeed affected by focal length. but change the camera position and all the lines change. This is perspective, the relationships of objects to one another. But that isn't what you've just described. You've only described directions from the camera to parts of the subject. A telephoto lens has a look because it is commonly used at greater distances from main subject. Again, this is just not necessarily true. That telephoto look occurs regardless of distance. Long lenses are often used for portraiture at fairly close distances, and I have already mentioned table-top photography. There are many macro lenses (i.e., designed expressly for macro work) in the 90mm to 200mm range, and of course they are used at close distances. In all of these examples the long-lens look is still there. You do not get the same perspective with a 180mm macro that you do with a 50mm macro. similarly wide angle lenses have a look because their wide field of view and great DOF is commonly used to include subjects close to the camera as they relate to subjects further away. Wide-angle lenses are very commonly used for landscapes and other distant shots, and DoF has nothing to do with perspective. But the focal length itself has no bearing on the perspective. As just (and repeatedly, repeatedly, repeatedly) illustrated, it does indeed. Choices made by lens designers affect how the scene is projected onto the film/sensor plane, but they do not affect perspective. This is actually pretty fundamental to photography, and the only reason that some of us have gone on about this is in the hope that perhaps someone might learn something. That is my hope. Or at least, UNLEARN some of the nonsense they have learned. |
#374
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"mcgyverjones" wrote in message . .. "Nostrobino" wrote in message ... "Jeremy Nixon" wrote in message ... Nostrobino wrote: I'm being generous. It might be called a spherical projection in the sense that, if you represent the position of the object relative to the camera in spherical polar coordinates (two angles and a distance), then the position of the image point corresponding to the object is determined by the two angles (but not the distance). But you're right, it's not really a projection of a sphere onto a flat surface, and not a spherical projection in the cartography sense. Anyway, you're still the only person in the entire world who thinks that focal length affects perspective. No, it's a common misconception. It's a common and correct perception. Actually, no, I'm far from "the only person in the entire world who thinks" that. Anyone who can see what's in front of him (and whose reasoning power has not been destroyed by reading nonsense) can see that a photo taken with a wide-angle lens has an entirely different perspective from a photo taken with a long lens from the same position. Unfortunately, you appear to be one of those so afflicted; as I recall you insisted repeatedly that there is "no such thing as a telephoto look," etc. There is a telephoto look, it is derived from the distances that telephoto photographs are commonly taken at. The telephoto look (i.e., perspective) occurs with long lenses irrespective of camera to subject distance. Do table-top photography with a long lens and you still have the telephoto look. Jeremy, the problem here is that you're trying to see the world aroundyou as the inside surface of a sphere, which it simply is not. It's a three-dimensional world, made up of three-dimensional objects, and all a rectilinear lens does is create a two-dimensional representation of those objects, whatever is in front of it that it's able to view. And how does it do that? If it's not a spherical projection, what is it? You can't just say it makes a 2D representation of a 3D world; there has to be a method of doing that. Anyway, I'm not asking you, I'm basically done with you. Go in peace then, brother, and enjoy the sphericity of your spherical world. So you really are a flat-earther? No, I'm a three-dimensionaler. So you're agreeing with Jeremy that it's all a spherical projection? Actually, this whole sphere thing (as fascinating as it may be to some) is irrelevant to perspective. You will want to talk to Jeremy about that, not me. To demonstrate how perspective can only be affected by camera position, YES! YES! That is exactly what I have been asking people here to do, and have had no takers. Just show me how you can get the same perspective with a 135mm lens (or whatever) that you do with a 28nn lens (or whatever). Use any camera position you like to do that. imagine various straight lines between the camera and subjects (fore, mid and background). These lines represents the path of the cameras line of site, or of light travelling from subject to camera. So far, so good. These lines define the subject's relationship to one another and the background. No, sorry, they do not. They define nothing but the directions from the camera to those parts of the subject(s). Of course they are not affected by focal length, Change the focal length and you get MORE such lines at wider angles, or FEWER such lines at narrower angles. The lines you had before the f.l. change are either added to, or subtracted from. Ergo, they are indeed affected by focal length. but change the camera position and all the lines change. This is perspective, the relationships of objects to one another. But that isn't what you've just described. You've only described directions from the camera to parts of the subject. A telephoto lens has a look because it is commonly used at greater distances from main subject. Again, this is just not necessarily true. That telephoto look occurs regardless of distance. Long lenses are often used for portraiture at fairly close distances, and I have already mentioned table-top photography. There are many macro lenses (i.e., designed expressly for macro work) in the 90mm to 200mm range, and of course they are used at close distances. In all of these examples the long-lens look is still there. You do not get the same perspective with a 180mm macro that you do with a 50mm macro. similarly wide angle lenses have a look because their wide field of view and great DOF is commonly used to include subjects close to the camera as they relate to subjects further away. Wide-angle lenses are very commonly used for landscapes and other distant shots, and DoF has nothing to do with perspective. But the focal length itself has no bearing on the perspective. As just (and repeatedly, repeatedly, repeatedly) illustrated, it does indeed. Choices made by lens designers affect how the scene is projected onto the film/sensor plane, but they do not affect perspective. This is actually pretty fundamental to photography, and the only reason that some of us have gone on about this is in the hope that perhaps someone might learn something. That is my hope. Or at least, UNLEARN some of the nonsense they have learned. |
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