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Thread: Four thirds, telephoto lenses and perspective compression. (question)

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    Four thirds, telephoto lenses and perspective compression. (question)

    This may be a silly question, I'm probably over thinking it.

    I know a telephoto lens compresses the perspective. The longer the telephoto the more the effect. At least on the DPreview forums people keep saying 150mm is 150mm and it's just a crop to get a 300mm angle of view. Would that mean a picture taken with the 150mm on a Olympus would have a view then a 300mm lens on something like a D700? The full frame camera compressing the perspective more then the Olympus? Ignoring DoF field differences etc.

    Thanks,
    Charles

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    i believe the telephoto compression effect is simply a function of distance to subject. as you get farther away, the image will get smaller, so one uses more magnification, either by a longer fl lens or cropping a smaller portion of the image and enlarging, or both

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Perspective depends solely on camera position. A telephoto lens magnifies -- it doesn't actually compress the perspective, rather it brings far away things 'closer'.

    Using a telephoto won't alter the perspective, only the angle of view -- how much of the scene is recorded on the sensor.

    A smaller sensor records less image than a big sensor for the same focal length of lens.

    From the same camera position, an Olympus 4/3 sensor and a 150mm lens will record the same scene as a 'full frame' camera with a 300 mm lens [of course the sensors are slightly different shapes].

    Try taking a pic with a wide angle and a telephoto lens, and magnifying the centre of the wide angle pic; the perspective will be the same in both.

    Theoretically, all you need is a wide angle but rectilinear lens -- you can get the effect of a telephoto lens by magnifying a small area -- but, of course, the quality of the resulting pic is poor.
    Sláinte

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Thanks to both of you for your explanations. I was just over thinking the problem and what you said makes sense. Thanks!
    Charles - flickr

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by Robert Campbell View Post
    Perspective depends solely on camera position. A telephoto lens magnifies -- it doesn't actually compress the perspective, rather it brings far away things 'closer'.

    Using a telephoto won't alter the perspective, only the angle of view -- how much of the scene is recorded on the sensor.

    A smaller sensor records less image than a big sensor for the same focal length of lens.

    From the same camera position, an Olympus 4/3 sensor and a 150mm lens will record the same scene as a 'full frame' camera with a 300 mm lens [of course the sensors are slightly different shapes].

    Try taking a pic with a wide angle and a telephoto lens, and magnifying the centre of the wide angle pic; the perspective will be the same in both.

    Theoretically, all you need is a wide angle but rectilinear lens -- you can get the effect of a telephoto lens by magnifying a small area -- but, of course, the quality of the resulting pic is poor.
    Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".

    17mm (cropped): http://media.offcentric.com/17mm.jpg
    200mm: http://media.offcentric.com/200mm.jpg

    Setup: closest object placed at about 170cm from the camera, furthest object 4 meters.

    The difference isn't huge, but it's there. And it's not huge because my apartment isn't big enough for a bigger setup. I'd say to anyone in doubt, take your 2 lenses (or one zoom lens) outside, and try it for yourself. Flower in the foreground, mountain in the background for instance.

    Furthermore anyone in filmmaking will be quite aware of the "dolly in, zoom out" or conversely "dolly out, zoom in" techniques, used for example in many Alfred Hitchcock films. You can clearly and plainly see there what effect focal length has on perspective.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by indorock View Post
    Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".

    17mm (cropped): http://media.offcentric.com/17mm.jpg
    200mm: http://media.offcentric.com/200mm.jpg

    Setup: closest object placed at about 170cm from the camera, furthest object 4 meters.

    The difference isn't huge, but it's there. And it's not huge because my apartment isn't big enough for a bigger setup. I'd say to anyone in doubt, take your 2 lenses (or one zoom lens) outside, and try it for yourself. Flower in the foreground, mountain in the background for instance.

    Furthermore anyone in filmmaking will be quite aware of the "dolly in, zoom out" or conversely "dolly out, zoom in" techniques, used for example in many Alfred Hitchcock films. You can clearly and plainly see there what effect focal length has on perspective.
    Indorock, Strong words with fuzz supporting () your statements?

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    Senior Member ggibson's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by indorock View Post
    Furthermore anyone in filmmaking will be quite aware of the "dolly in, zoom out" or conversely "dolly out, zoom in" techniques, used for example in many Alfred Hitchcock films. You can clearly and plainly see there what effect focal length has on perspective.
    I'm still wrapping my mind around the concept as well, but indorock is right. Take a look at this video:

    http://www.youtube.com/watch?v=Y48R6-iIYHs

    A crop of 300mm =/= 150mm non-cropped.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    +1

    Quote Originally Posted by indorock View Post
    Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".

    17mm (cropped): http://media.offcentric.com/17mm.jpg
    200mm: http://media.offcentric.com/200mm.jpg

    Setup: closest object placed at about 170cm from the camera, furthest object 4 meters.

    The difference isn't huge, but it's there. And it's not huge because my apartment isn't big enough for a bigger setup. I'd say to anyone in doubt, take your 2 lenses (or one zoom lens) outside, and try it for yourself. Flower in the foreground, mountain in the background for instance.

    Furthermore anyone in filmmaking will be quite aware of the "dolly in, zoom out" or conversely "dolly out, zoom in" techniques, used for example in many Alfred Hitchcock films. You can clearly and plainly see there what effect focal length has on perspective.
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    The key difference is object distance. That makes every comparison relative. So at the same distance, a telephoto lens does compress the perspective. But a crop factor is just that, a crop factor. Doesn't change perspective characteristics.
    My 25mm lens will always give wideangle perspective, only cropped to 50mm equivalent.
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by laptoprob View Post
    My 25mm lens will always give wideangle perspective, only cropped to 50mm equivalent.

    Hmmm..that is incorrect.

    The key is magnification and that is what Robert said and there are others supporting a wrong notion.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Hi Cj

    [side steps arguments]

    firstly I find that the DoF that I get on the telephoto is slightly deeper than if I was using the same "equivalent" on a 35mm. I mean that a 200mm more or less has the same angle of view as a 400mm on a 35mm camera. But when I use the 200 on the G1 I get better DoF at f4 than if I was using a 400 on a 35mm or full frame.

    Some samples of a FD200 f4

    sorto of close


    mid distance



    far distance



    as to compression of field ... well ... that's a function of telephoto anyway :-)

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by indorock View Post
    Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".

    17mm (cropped): http://media.offcentric.com/17mm.jpg
    200mm: http://media.offcentric.com/200mm.jpg

    Setup: closest object placed at about 170cm from the camera, furthest object 4 meters.

    The difference isn't huge, but it's there. And it's not huge because my apartment isn't big enough for a bigger setup. I'd say to anyone in doubt, take your 2 lenses (or one zoom lens) outside, and try it for yourself. Flower in the foreground, mountain in the background for instance.

    Furthermore anyone in filmmaking will be quite aware of the "dolly in, zoom out" or conversely "dolly out, zoom in" techniques, used for example in many Alfred Hitchcock films. You can clearly and plainly see there what effect focal length has on perspective.
    Perspective is determined by the position of the center of perspective of the lens. This is also known as the entrance pupil. Unless you have taken care to make sure the location of the entrance pupil for your 17mm and 200mm lenses is exactly the same relative to your two objects then your experiment is invalid. Hint: If you simply kept the camera fixed and switched lenses then you've made a mistake!

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Brian, Very happy to see you here!

    [For those who do not know: Dr.Brian Caldwell is a professional lens designer.]

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Hello Brian

    Quote Originally Posted by brianc1959 View Post
    Unless you have taken care to make sure the location of the entrance pupil for your 17mm and 200mm lenses is exactly the same relative to your two objects then your experiment is invalid.
    not knowing enough to know why (but keen to be pointed at readings) are we talking about being out by much or just a little?

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Hi all:

    What Robert, Brian and others have said can be very easily verified by putting a zoom lens on a camera, attaching said camera to a tripod and zooming in and out. The magnification changes with focal length, but the perspective (i.e. the relationship between near and far objects) does not change.

    I just took a couple of test shots with my old Sony R1 since it has a greater zoom range, 5X, than my Panasonic kit zoom.

    The first image was taken at 120 mm equiv and simply downsized for posting.
    The second image was taken at 24 mm equiv, cropped, then upsized so that the fire hydrant was the same size as in the tele shot. Take note of the bird bath and the church in the background in relation to the fire hydrant.

    regards
    Santo

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    I forgot to include the full image taken at 24 mm.

    regards
    Santo

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    OK, I see... the dolly-zoom effect shows a changing perspective because the camera is moving towards or away from the focal plane. But two cameras with different crop factors at the same distance matched with equivalent lenses WILL show the same perspective.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    As the angular field of view of a 50mm lens on an M-4/3 camera is roughly the same as that of a 100mm lens on a full-frame camera, I would expect that the "perspective" in shots from each would be about the same (DOF aside).

    As for the discussion regarding "compression" etc., I think that the important part is to grasp -- visually -- the impact that using a wide angle or a telephoto may have on a subject and it's relationship to the background. It's why we may choose an 80-120mm lens for a more traditional head & shoulders portrait (full-frame), rather than a 17mm or 300mm (working distance aside).
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by indorock View Post
    Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".
    Just like yours!

    Buy a tripod and learn how to use it! Notice how the relative position of the chair has changed - you clearly moved in between shots completely invalidating your results.

    The difference isn't huge, but it's there. And it's not huge because my apartment isn't big enough for a bigger setup.
    It is there because you screwed up, see the properly done examples in this thread. Also, in your tiny apartment you need to account for the entrance pupil location of the lens which you failed to do. In fact, in a bigger setup the errors you made would be less accentuated and your erroneous result diminished.

    I'd say to anyone in doubt, take your 2 lenses (or one zoom lens) outside, and try it for yourself. Flower in the foreground, mountain in the background for instance.
    Ta-da! Someone did, and they got the results than anyone who understands anything about optics would expect!

    Furthermore anyone in filmmaking will be quite aware of the "dolly in, zoom out" or conversely "dolly out, zoom in" techniques, used for example in many Alfred Hitchcock films. You can clearly and plainly see there what effect focal length has on perspective.
    Anyone who knew what they were talking about would understand that that dolly in/zoom out is changing perspective because the dolly moved. Duh! That's what everyone has been saying.

    In the future when making flame-bait posts at least try to know what you are talking about first, it will go over a lot better.

    Ken

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by indorock View Post
    Patently and totally incorrect.
    I missed the fun here -- too busy trying to print. I had to search a little for the source of my contention that perspective depends solely on your position -- it came from John Hedgecoe's The Photographer's Handbook [1977]. He was Professor of Photography at the Royal College of Art [now emeritus].There is a description with pix on pp 104-105.

    Magnification with lenses. Image magnification varies according to focal length. You might argue that everything could be shot with a wid-angle lens and the required picture area enlarged from the negative through the enlarger.To show just how different the result would be, the picture, below right, is from a whole negative taken with a 500mm lens. The one, below left, is enlarged from the center of the 40 mm lens negative. Immediately you can see that the depth of field is much shallower with the long-focus lens. The degree of enlargement given to the 40mm negative has also increased its graininess destroying fine detail. The result is an image which has been flattened in tone, even though perspective and scale remain in each picture.
    [My italics]
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    This fascinating collision of fact and opinion illustrates a phenomenon that is explained in a famous research paper (link to PDF) by Justin Kruger and David Dunning titled Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments.
    People tend to hold overly favorable views of their abilities in many social and intellectual domains. The authors suggest that this overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it. Across 4 studies, the authors found that participants scoring in the bottom quartile on tests of humor, grammar, and logic grossly overestimated their test performance and ability. Although their test scores put them in the 12th percentile, they estimated themselves to be in the 62nd. Several analyses linked this miscalibration to deficits in metacognitive skill, or the capacity to distinguish accuracy from error. Paradoxically, improving the skills of participants, and thus increasing their metacognitive competence, helped them recognize the limitations of their abilities.
    The corollary to unskilled individuals overestimating their ability ("the less I know, the more I think I know") is that skilled individuals consistently underestimate their ability ("the more I know, the more I realize how much I still have to learn").

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by indorock View Post
    Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".
    Funny guy, huh?

    Of course, and as stated clearly in Robert Campbell's very informative post, focal length has nothing to do with perspective. It's camera distance to the subject that governs perspective. If you don't believe it, I guess you could use some time with a few good technical books on the subject.

    Cheers!

    Abbazz

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by Vivek View Post
    Brian, Very happy to see you here!

    [For those who do not know: Dr.Brian Caldwell is a professional lens designer.]
    Hi Vivek:
    Thanks - and good to see you here as well. I originally found this site because I was (and am) interested in medium format digital backs, but I've recently become a big fan of micro fourthirds and this seems to be the best forum around.

    Brian

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by pellicle View Post
    Hello Brian



    not knowing enough to know why (but keen to be pointed at readings) are we talking about being out by much or just a little?
    Out by enough to make the wrong conclusion. Wide angle lenses tend to have their entrance pupil near the front element, whereas the entrance pupil shifts back toward the image plane in telephoto lenses. So, you would have to move camera and lens closer to the object when taking the tele shot in order to have the telephoto entrance pupil coincide with the position of the wide angle entrance pupil.

    The effect of making an error is greater when photographing closeup subjects because the error of entrance pupil placement in the two setups is a sizeable fraction of the object-image distance. If the poster had done the experiment outdoors with a more distant subject the error would have been much smaller and he probably wouldn't have jumped to the wrong conclusion.

    Note: The entrance pupil of a lens is often mistakenly called the nodal point by people doing stitched panoramas. Its easy to find using the parallax method if you've got a pano head on a tripod.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by pellicle View Post
    Hello Brian



    not knowing enough to know why (but keen to be pointed at readings) are we talking about being out by much or just a little?
    Out by enough to make the wrong conclusion. Wide angle lenses tend to have their entrance pupil near the front element, whereas the entrance pupil shifts back toward the image plane in telephoto lenses. So, you would have to move camera and lens closer to the object when taking the tele shot in order to have the telephoto entrance pupil coincide with the position of the wide angle entrance pupil.

    The effect of making an error is greater when photographing closeup subjects because the error of entrance pupil placement in the two setups is a sizeable fraction of the object-image distance. If the poster had done the experiment outdoors with a more distant subject the error would have been much smaller and he probably wouldn't have jumped to the wrong conclusion.

    Note: The entrance pupil of a lens is often mistakenly called the nodal point by people doing stitched panoramas. Its easy to find using the parallax method if you've got a pano head on a tripod.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by Abbazz View Post
    Of course, and as stated clearly in Robert Campbell's very informative post, focal length has nothing to do with perspective. It's camera distance to the subject that governs perspective.
    Yes, BUT... it's focal length that determines the camera to subject distance, and therefore it's focal length that I choose in order to obtain a particular perspective.

    One can fill a frame top to bottom with a person's face using a 17mm lens very close, or a 100mm lens from much farther away (or 8mm and 50mm in 4/3 format). Aside from an uncomfortable working distance, the perspective provided by using the 17mm lens that close is unnatural and unflattering.

    Or think of product photography. Assuming the size of the product in the frame remains the same (when shot), the look of the product can be very different depending on the focal length of the lens (not to mention swings, tilts and shifts!).

    I guess what I'm saying is that I think of perspective in terms of focal length rather than in terms of distance from subject. And I'll bet many others do, too. If I see a silhouette of a person against a giant ball of a setting sun I don't think "cripes, that photographer was a long way away from the subject", or "man, that must be a tiny crop from a much larger picture". I think "big telephoto".
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Yes, most people think of focal length. But I think subject distance is the better way of considering perspective, then you avoid all the ambiguities and arguments posed in this thread (I was unsure of the answer myself.)

    Subject distance is the same, regardless of whether you are shooting M 4/3, full frame, small compact, or your cell phone. But focal length will vary widely depending on the camera (even though normally we all think in terms of 35mm full frame 'equivalent' so when you say 17mm, I know what you mean.)

    At least for me, this whole issue about perspective cleared up completely when I realized that subject distance is what we are really talking about- that made it more inherently 'graspable' for me.

    Quote Originally Posted by JBurnett View Post
    Yes, BUT... it's focal length that determines the camera to subject distance, and therefore it's focal length that I choose in order to obtain a particular perspective.

    One can fill a frame top to bottom with a person's face using a 17mm lens very close, or a 100mm lens from much farther away (or 8mm and 50mm in 4/3 format). Aside from an uncomfortable working distance, the perspective provided by using the 17mm lens that close is unnatural and unflattering.

    Or think of product photography. Assuming the size of the product in the frame remains the same (when shot), the look of the product can be very different depending on the focal length of the lens (not to mention swings, tilts and shifts!).

    I guess what I'm saying is that I think of perspective in terms of focal length rather than in terms of distance from subject. And I'll bet many others do, too. If I see a silhouette of a person against a giant ball of a setting sun I don't think "cripes, that photographer was a long way away from the subject", or "man, that must be a tiny crop from a much larger picture". I think "big telephoto".

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by JBurnett View Post
    Yes, BUT... it's focal length that determines the camera to subject distance, and therefore it's focal length that I choose in order to obtain a particular perspective.

    One can fill a frame top to bottom with a person's face using a 17mm lens very close, or a 100mm lens from much farther away (or 8mm and 50mm in 4/3 format). Aside from an uncomfortable working distance, the perspective provided by using the 17mm lens that close is unnatural and unflattering.
    Yes, but: I saw a demo of this years ago. A portrait taken with a wide angle, and projected onto a large scren. One viewer was put up close to the screen, and asked for comments. He was so close to the picture that the 'distortion' that the rest of us, sitting farther away saw, wasn't apparent to him.
    Sláinte

    Robert.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Brian,

    Thanks for the bit about entrance pupils and perspectice -- I didn't know that. Hedgecoe's pictures are of an old gent in a field, and taken from a distance, so the entrance pupil change is pretty insignificant [I think it's Hedgecoe senior in the pix]

    Quote Originally Posted by brianc1959 View Post
    Note: The entrance pupil of a lens is often mistakenly called the nodal point by people doing stitched panoramas. Its easy to find using the parallax method if you've got a pano head on a tripod.
    Quite; so some people refer to the 'no parallax point'.
    Sláinte

    Robert.

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by JBurnett View Post
    Yes, BUT... it's focal length that determines the camera to subject distance, and therefore it's focal length that I choose in order to obtain a particular perspective.
    I work the other way round: I determine the distance to the subject considering the perspective I want to get, then I choose the lens according to the angle of view needed. An example: in order to avoid to exaggerating facial features in a portrait, I know that I have to stand at least 1.5m from the subject, so I will choose the lens according to the kind of portrait I need to achieve at a distance greater than 1.5m (on 135, it means a 135mm for a mugshot, a 85mm for half body and a 35mm for full body).

    That's why people saying "zoom with your feet" make me laugh. You cannot zoom with your feet: if you change position relative to your subject, the perspective changes and you don't get the same picture as if you used a different focal length from the same standpoint.

    Cheers!

    Abbazz

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    Senior Member pellicle's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Brian

    Quote Originally Posted by brianc1959 View Post
    Out by enough to make the wrong conclusion.
    ...
    The effect of making an error is greater when photographing closeup subjects
    ...
    by people doing stitched panoramas. Its easy to find using the parallax method if you've got a pano head on a tripod.
    ahh hah ... that explains much ... takes me back to my optics work at uni in 1981

    thanks!

  32. #32
    ChrisJ
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by cjlacz View Post
    This may be a silly question, I'm probably over thinking it.

    I know a telephoto lens compresses the perspective. The longer the telephoto the more the effect. At least on the DPreview forums people keep saying 150mm is 150mm and it's just a crop to get a 300mm angle of view. Would that mean a picture taken with the 150mm on a Olympus would have a view then a 300mm lens on something like a D700? The full frame camera compressing the perspective more then the Olympus? Ignoring DoF field differences etc.

    Thanks,
    Charles
    There's a lot of flexing of optical muscle here, unfortunately not a lot of them have actually answerd Charles's question.

    Charles you are right, a 150mm lens will behave as a 150mm lens as far as compression or any other criteria is concerned, and likewise for the 300mm lens, the 300mm lens will have more compression. The fact that the different cameras crop a different size from the projected image is neither here nor there.

    Chris

  33. #33
    Super Duper
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by brianc1959 View Post
    Hi Vivek:
    Thanks - and good to see you here as well. I originally found this site because I was (and am) interested in medium format digital backs, but I've recently become a big fan of micro fourthirds and this seems to be the best forum around.

    Brian
    Hi Brian,

    The forum is owned by couple of photographers and the folks its continue to attract are pretty level headed (as exemplified by this very thread).

    Great set-up and great folks.

    Very good to have you here. It will be a great benefit to one and all.

  34. #34
    Member kwalsh's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by ChrisJ View Post
    There's a lot of flexing of optical muscle here, unfortunately not a lot of them have actually answerd Charles's question.
    Actually, if you look at the first four posts it appears the question was answered to the OP's satisfaction back in 2008. The real mystery is why indorock revived it from the dead

  35. #35
    Abbazz
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by kwalsh View Post
    Actually, if you look at the first four posts it appears the question was answered to the OP's satisfaction back in 2008. The real mystery is why indorock revived it from the dead
    ...only to add incorrectly -- and rather abruptly -- that perspective depends on focal length. A 300mm lens doesn't "compress" more than a 150mm lens, whatever camera you put it on!

    Cheers!

    Abbazz

  36. #36
    Member sangio's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by brianc1959 View Post
    Out by enough to make the wrong conclusion. Wide angle lenses tend to have their entrance pupil near the front element, whereas the entrance pupil shifts back toward the image plane in telephoto lenses. So, you would have to move camera and lens closer to the object when taking the tele shot in order to have the telephoto entrance pupil coincide with the position of the wide angle entrance pupil.

    The effect of making an error is greater when photographing closeup subjects because the error of entrance pupil placement in the two setups is a sizeable fraction of the object-image distance. If the poster had done the experiment outdoors with a more distant subject the error would have been much smaller and he probably wouldn't have jumped to the wrong conclusion.

    Note: The entrance pupil of a lens is often mistakenly called the nodal point by people doing stitched panoramas. Its easy to find using the parallax method if you've got a pano head on a tripod.

    Because I like to make stitched panoramas, I've determined the nodal point (OK, OK the entrance pupil) for the Panasonic 14 - 45 zoom at various focal lengths. When zooming from 14 to 45 mm, the entrance pupil moves back about 10 mm.

    The attached image was taken on Lago Maggiore, Italy, this past May, using the G1 and the 14 - 45 kit lens. The dimension of the stitched file is 7200 x 2600 pixels.

    BTW if someone can tell me how to attach images so that they show up as regular images, not thumbnails, I'd greatly appreciate it.

    regards
    Santo

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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by sangio View Post
    .........
    BTW if someone can tell me how to attach images so that they show up as regular images, not thumbnails, I'd greatly appreciate it.

    regards
    Santo
    Santo, you have to upload them to your free gallery first. Then the URL shown under your image in the gallery needs to be copied down to your post. I use the little yellow mountain icon at the top of the message box.

    Keith

  38. #38
    turbo
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    [QUOTE=indorock;149352]Patently and totally incorrect. It's funny how the internet is full of opinions without supporting evidence, haphazardly stated as "facts".


    Reminds me of a 'News' item in The Onion.

    "The Information Age was dealt a stunning blow Monday, when a factual
    error was discovered on the Internet."

  39. #39
    Senior Member ggibson's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by kwalsh View Post
    Actually, if you look at the first four posts it appears the question was answered to the OP's satisfaction back in 2008. The real mystery is why indorock revived it from the dead
    Bah, I can't believe I was caught by a necro. I usually check these things.

  40. #40
    Senior Member pellicle's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Quote Originally Posted by ggibson View Post
    Bah, I can't believe I was caught by a necro. I usually check these things.
    you stole a prisoner from them!

  41. #41
    Senior Member pellicle's Avatar
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    Re: Four thirds, telephoto lenses and perspective compression. (question)

    Chris

    Quote Originally Posted by ChrisJ View Post
    The fact that the different cameras crop a different size from the projected image is neither here nor there.
    well that may be so for your compositional technique, but mine does care about that ;-)

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