What’s Your Preference?

FotoMike · #1 (**permalink**) 05-06-2008, 06:39 PM

I really love this shot of a church in Yosemite National Park, but to me it seems like its leaning a little to the right and I can't seem to fix it. Am I the only one that notices this? Am I crazy? Thanks for the help

Mr Guy · #2 (**permalink**) 05-06-2008, 09:21 PM

I think it's an optical illusion. Everything in the picture is leaning to the right, the trees, even the cracks in the mountain. Meanwhile, there are horizontal lines on the front of the tower that you expect to be perfectly level from that vantage point, but they are actually sloping down. My hunch is they actually are not parallel to the ground on that face.

If you obscure that face, the effect vanishes.

The reason you can't fix it is because the strong vertical lines on the church are spot on 90 degrees, so any budging makes them look off.

At least, that's my take on what's happening.

xxpinballxx · #3 (**permalink**) 05-07-2008, 10:52 AM

the right side of shot was off a degree or so to the left....I threw it in CS3 lens distortion filter and corrected a bit....this any better....

PhotoNewt · #4 (**permalink**) 05-07-2008, 04:26 PM

What lens did you use to take this picture with? What focal length was it set at? Is this a crop from a bigger picture? Just curious, looks a little like barrel distorsion.

FotoMike · #5 (**permalink**) 05-10-2008, 06:32 AM

Sorry to get back to everyone so late.

EXIF:
F/5.0 @ 1/1000 shot at 33mm.
taken with canon 18-55mm kit lens

not sure i really know what barrel distortion is. can you elaborate?

zetson · #6 (**permalink**) 05-10-2008, 11:38 AM

If you take a picture of a building from a low point of view, the building will be smaller on the top than on the ground. This effect can be corrected in PS with the transformation tool. I thought that was the problem with your picture so I tried that in PS, but it didn't work... Strange.

PhotoNewt · #7 (**permalink**) 05-10-2008, 03:03 PM

Quote:

Originally Posted by zetson

If you take a picture of a building from a low point of view, the building will be smaller on the top than on the ground...

The effect you described above is called curvilinear distorsion is a function of the viewpoint of the camera relative to the subject and not a flaw of the lens system itself. The most well known examples, besides buildings as described, is a train track or a long straight road where the lines seem to converge towards infinity. For the lines to record straight they need to be projected parallel to the sensor (film) plane - this is how a perspective correction lens usually works.

Barrel distorsion is an optical flaw of the lens system mostly present at wide angle settings (below 35-40mm). Is most common in complex zoom systems and is caused by changes in distance between floating elements inside the barrel needed to adjust the focal length (that is why the barrel extends when you move the ring from 18 to 55mm). This distorsion is almost non-existent on wide angle prime lenses or high quality short wide angle zooms.

As the name implies it will make a picture with straight lines (like a building) adopt the shape of a barrel, where lines near the center will be straight but those more peripheral will curve towards the borders.

Go to this review page so you can see an illustrastion of barrel distorsions caused by the Canon EF-S 18-55mm f/3.5-5.6 II kit lens. If your system is Nikon, this is the same illustration but for the Nikkor AF-S 18-55mm f3.5-5.6 G ED DX kit lens.

FotoMike · #8 (**permalink**) 05-10-2008, 05:30 PM

PhotoNewt I don't think that could have been any clearer of an explanation thank you for the help that really makes a lot of sense now. I see now, since I shot it at 33mm that barrel distortion might have been the problem in this picture.