Probably a stupid question...

Discussion in 'Photography Beginners' Forum' started by LisaMarie, Apr 19, 2009.

  1. LisaMarie

    LisaMarie TPF Noob!

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    Well its still early here where i live so this may be another one of those "stupid questions" but here i go anyways! So if i was to use a wide lens on a croped sensor body would i get the same effects if i was to have a basic lens on a full frame sensor body camera.

    Also if i was shooting a picture with a wide lens, then decided to switch to just say a basic zoom lens, and then stepped back a few meters to re shoot the same image would i have capture the same image as when i was using the wide lens, or does a wide lens also do some slight horizontal cropping top and bottom to achieve those widening affects??
     
  2. DScience

    DScience No longer a newbie, moving up!

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    Well the wide lens is always going to give you a different effect on the photo, when compared to a non wide angle lens. It's very difficult to simulate the effect you get with a wide angle lens, by using a normal zoom lens.

    Sorry I could not be more specific
     
  3. Dwig

    Dwig TPF Noob!

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    Your use of the terms "wide lens" and "basic lens" are a bit confused. "Wide Angle" refers to a lens' angular coverage on its intended format. When you use a lens on a different format, the term may become incorrect. A 28mm lens designed for 35mm film (or equivalent digital) would be a wide angle lens and would act like a wide angle lens when used on that format. If used on a smaller format (e.g. the common "cropped sensor" APS-c format) it would act like a normal lens.

    No, the primary effect seen with wide angle lenses is not a product of the lens. It is a product of the shooting distance, and only the shooting distance. The only thing the lens contributes is the wider field of view which allows you to work at a closer distance.

    As you move closer to a subject, the ratio between the camera-to-subject distance and the camera-to-background distance changes. It is this ratio that creates the perspective effect characteristic to a wide angle lens or a telephoto lens.
     
  4. gryphonslair99

    gryphonslair99 Been spending a lot of time on here!

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    Sorry, but I would have to disagree. The focal length of a lens does add characteristics to a lens. A 50mm lens gives the closest prospective view to the human eye. The prospective of a wide angle lens tends to widen features, where as the prospective of a telephoto lens above 50mm tends to compress features. This is most noticeable when shooting portraits and unobservable when shooting something like landscaped or general scenes. This is also one of the reason that standard portraits are shot with a short to medium telephoto.

    The distance ratio to subject only changes what is covered in the field of view in relationship to the field of view of the lens.
     
  5. Dwig

    Dwig TPF Noob!

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    You are quite wrong. For your statement to be at all valid, you have to specify that you are discussing the use of a 50mm lens on a camera with approximately a 24x36mm image area, film or digital sensor. If the camera is any other format, you reference to a 50mm lens is wrong. Either way, its not the fact that the lens has a 50mm focal length that creates the effect. Its that a 50mm lens causes the user to stand a certain distance from a subject to get a certain framing. If, and only if, the image is printed full frame, uncropped at an appropriate size for the viewing distance, it will display a perspective close to what a view would consider "normal'.

    Its not some magic of the 50mm focal length. If you were to crop the image significantly, enlarging that cropped portion to the size of the first print, the image a viewer would percieve the perspective of a telephoto with the associated "compression" of spatial depth.
     
  6. gryphonslair99

    gryphonslair99 Been spending a lot of time on here!

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    By your reasoning then, a Fisheye lens would cease to give a fisheye perspective if only I stood far enough back and it is used on a crop body sensor. Funny, my fisheye doesn't seem to conform to the theory on a FF or a crop sensor body.
     
  7. tsaraleksi

    tsaraleksi TPF Noob!

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    A fisheye is a unique case because it is designed to cause optical distortion. Otherwise, the distortion/perspective of a lens is all an artifact of where it makes you stand in relation to a subject, which is why a 50mm lens on a crop body makes a flattering portrait lens-- because when using it, you stand the same distance that you might stand if you were using an 80mm lens on a full frame or film body.
     
  8. Jaszek

    Jaszek No longer a newbie, moving up!

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    To Dwig. Look at the example below. It was taken with a 10-20mm lens @10mm (which would be the same if you used a 16-35mm lens @16mm ion a full frame considering a 1.6 crop factor) and you can clearly see how the buildings on the left and right of the frame are leaning inwards. If I shot this with lets say my 18-55mm @18mm and stepped back to get the same FOV the buildings wouldn't be leaning inwards due to the less convex glass in the 18-55.
    [​IMG]
     
  9. tsaraleksi

    tsaraleksi TPF Noob!

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    Exactly. Because you would change where you were standing, you would change the image's perspective. However, you could take this image with a 16-35 on full frame and get the same perspective and image.
     
  10. gryphonslair99

    gryphonslair99 Been spending a lot of time on here!

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    The physics of a lens does not change due to the size of the sensor. A crop sensor is merely using the center of the field of view provided by the lens. The sensor, as with film, is mearly a flat media for recording images. Your ability to perceive the changes does change with the distance of the subject to the focal plane. But only because your eyes and brain are not good enough to detect the perspective distortion. Now if you are talking about a Telecentric lens then that is different. A Telecentric lens is engineered to correct perspective distortion at a particular focal length. That is why Telecentric lenses are used for precise measurments.





     

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