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Archive 2015 · Crop sensors and their perspective changes.

  
 
rw11
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p.2 #1 · p.2 #1 · Crop sensors and their perspective changes.


more like bronze approximations


Apr 27, 2015 at 01:08 PM
Monito
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p.2 #2 · p.2 #2 · Crop sensors and their perspective changes.


And this would be the arsenic pit:

rw11 wrote:
why don't we argue that it is really reproduction ratio not distance that matters


Reproduction ratio has nothing to do with perspective.

Distance to objects in the scene is the only thing that affects perspective. This determines the relative size of objects in the scene.

Prints made from several cameras at the same position will have the same perspective, regardless of the focal length, print size, sensor size, or viewing distance.

Objects in each print will have the same relative sizes to each other. It doesn't matter if the crop factor camera used a 50 mm lens and the 8x10 camera used a 450 mm lens. Similarly it doesn't matter if the crop factor camera used a 350 mm lens and the 8x10 camera used a 60 mm lens. Likewise, it doesn't matter if one print is 8x10 inches and another print is 80 x 100 cm. It doesn't matter if one print is viewed from 16 inches away and another is viewed from 16 feet away.

Once the picture is taken, the perspective is fixed.

Apparent perspective is a different matter. That depends on viewing distance and print size and crop factor (angle of view). There is no such thing as "telephoto perspective" or "wide angle perspective".

Make a photo from a fixed position with one camera with a 24 mm lens and a 50 mm lens and a 100 mm lens. Make an 8x12 inch print of each. View the 24 mm image from 10 inches, the 50 mm image from 20 inches, and the 100 mm image from 40 inches. They will all appear to have the same amount of, or lack of, focal length 'distortion'.

Likewise if you make a 32 x 48 inch print of the 24 mm image, a 16 x 24 inch print of the 50 mm image, and an 8 x 12 inch print of the 100 mm image and view them from the same distance (say 20 inches), they will all look equally 'distorted' and equally 'undistorted'.



Apr 27, 2015 at 03:46 PM
rw11
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p.2 #3 · p.2 #3 · Crop sensors and their perspective changes.


some of you can benefit from these:

http://en.wikipedia.org/wiki/Angle_of_view#Calculating_a_camera.27s_angle_of_view

http://en.wikipedia.org/wiki/Perspective_distortion_%28photography%29#Angle_of_view_of_the_capture



Apr 28, 2015 at 12:47 AM
AJSJones
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p.2 #4 · p.2 #4 · Crop sensors and their perspective changes.


rw11 wrote:
some of you can benefit from these:

http://en.wikipedia.org/wiki/Angle_of_view#Calculating_a_camera.27s_angle_of_view

http://en.wikipedia.org/wiki/Perspective_distortion_%28photography%29#Angle_of_view_of_the_capture


The second link describes perspective distortion
Perspective distortion is determined by the relative distances at which the image is captured and viewed, and is due to the angle of view of the image (as captured) being either wider or narrower than the angle of view at which the image is viewed, hence the apparent relative distances differing from what is expected.
I have no problem with this and sometimes look at my wideangle prints from a very close distance to "undo" the distortion. Print size and viewing distance both play into "reproduction ratio" as you mentioned. The distinction being made here is between simple "perspective", as defined solely by camera position (and it fixes the relationships of objects in the image to one another) and "perspective distortion" which relates to what the observer sees when viewing the printed/projected image and mentally comparing it to what the image represents - such comparison being perceived as "distortion". Thus in an acquired image, the perspective is fixed but the amount of perspective distortion can be varied by print size and viewing distance.

Tilting the sensor plane away from vertical (or away from parallel to image lines) will cause some images to be recorded in a distorted manner and this is sometimes referred to as "wide-angle perspective" when it should actually be referred to (as your link describes) as "perspective distortion". When we see a typical image of a road or railway receding into the distance (taken with the sensor plane at right angles to the lines), the lines converge, as the brain expects. However, when the sensor plane is not parallel to vertical lines of e.g., buildings, those lines converge unnaturally and the "distortion" is immediately noted by the brain.

In all cases, whether "distortion" is perceived or not, the perspective was fixed at time of capture by the position of the camera (or more accurately, as the first link specifies "the center of perspective of a rectilinear lens is at the center of its entrance pupil")



Apr 28, 2015 at 04:27 PM
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