03-20-2013, 07:43 AM
Hi Aaron,
welcome to the forum.
With a wide angle lens, there are two types of distortion one should be aware of. One is the distortion of the lens itself, which we measure.
If you point a lens towards an imagined rectangular (like our distortion test chart) and align the lens perfectly parallel, then you can see the lens' distortion in the resulting image. Either none (very rare), barrel distortion (side of the rectangular bent outwards) or pincushion distortion (bent inwards).
Now imagine you shoot that rectangular from below. The bottom of the rectangular will be closer to you and the upper part further away. Consequently, the sides of the rectangular will be tilted towards the center of the image.
This is geometric distortionm, caused by the angle of view and not the lens. You have this with any lens, but it's most often seen with wide angle lenses.
Geometric distortion is what you see in the sample images.
It can be avoided by aligning the camera parallel to the subject. But that's of course not always possible - imagine yourself standing in front of a large building. If you shoot from the ground upwards, the building will be tilted as described above. If you shoot parallel, half of the image will show the ground before you... and probably not the whole building.
-- Markus
welcome to the forum.
With a wide angle lens, there are two types of distortion one should be aware of. One is the distortion of the lens itself, which we measure.
If you point a lens towards an imagined rectangular (like our distortion test chart) and align the lens perfectly parallel, then you can see the lens' distortion in the resulting image. Either none (very rare), barrel distortion (side of the rectangular bent outwards) or pincushion distortion (bent inwards).
Now imagine you shoot that rectangular from below. The bottom of the rectangular will be closer to you and the upper part further away. Consequently, the sides of the rectangular will be tilted towards the center of the image.
This is geometric distortionm, caused by the angle of view and not the lens. You have this with any lens, but it's most often seen with wide angle lenses.
Geometric distortion is what you see in the sample images.
It can be avoided by aligning the camera parallel to the subject. But that's of course not always possible - imagine yourself standing in front of a large building. If you shoot from the ground upwards, the building will be tilted as described above. If you shoot parallel, half of the image will show the ground before you... and probably not the whole building.
-- Markus
Editor
opticallimits.com
opticallimits.com