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tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 18, 2010 - 02:32pm PT
bump for HD avalanche pics
HighTraverse

Trad climber
Bay Area
Feb 18, 2010 - 02:37pm PT
The "perspective" corrections are rotations in 3D... the lens "corrections" are higher order polynomials that take out the effects of the lens, which are primarily spherical expansions of the images around the lens axis.

Ed's completely correct on this but let me try to simplify.
Take a flat object and look straight at it. Now tilt it. The object is still flat but due to perspective (remember perspective in line drawings?) it will appear distorted. This is what you see when you look up at a tall object close by (such as a tall tree or a big wall). It's why someone further away looks shorter than up close. The top of the tree is much further away from your eyes than the base. It's why you can clearly see the haulbag at Stovelegs and can't see it at the top even with binoculars.
It's why tradster's trees are tilted towards each other (further away objects like the tops of the trees appear closer to each other)
Perspective is easily corrected in the image with basic image editing tool, because it's a linear function. That's why Ed was able to correct the image.

Perspective is different from lens distortion.
The most commonly seen lens distortion is "fisheye" when a "closeup" lens is used. You've seen the deliberate fisheye effect in many popular images where straight lines away from the center of the image appear to be curved. in some images the outside "straight" lines even make a circle.
This is entirely due to lens distortion, independent of (although can be combined with) perspective. Lens distortion is much harder to correct because it's non-linear.

OK, so I probably didn't make it any simpler or more obvious.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 18, 2010 - 05:26pm PT
Awesome photos Mike...thanks for posting them. As mentioned above I was at Mirror Lake meadow when this happened and got a clear view of it but didn't get my camera out of my pack in time. Did you also hear what sounded like rockfall ~10 minutes before the avalanche?
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