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R.Harpst
23rd of December 2006 (Sat), 00:36
I took this one tonight of a Church in Houston, What I need to know is why the back building is not straight. I checked the levels on the tripod and it showed to be level. Could it just be the angle that it was shot at... any help or advise would be greatly appreciated...
Radtech1
23rd of December 2006 (Sat), 01:00
Could it just be the angle that it was shot at... any help or advise would be greatly appreciated...

Yes, that happens when the line of sight through the lens is not horizontal. By pointing the camera up, even a little bit up, this is the result. To fix it, Photoshop (Full and elements both) have a correction called "Perspective". Skill lever on that would be "Novice"

Rad
Radtech1
23rd of December 2006 (Sat), 01:06
Played with:
JimHejl
23rd of December 2006 (Sat), 01:20
Ah, I know the answer to this one -- we deal with it every day in video game development. It's perspective distortion. When you use a wide-angle lens (in our terms, large fov-y) the distortion is magnified.

The two basic concepts are:
- Objects are drawn smaller as their distance from the observer increases
- The distortion of items when viewed at an angle (spatial foreshortening)

These apparent distortions are more pronounced away from the center of the image as the angle between a projected ray (from the scene to the sensor) becomes more acute relative to the picture plane.

As said above, photoshop can be used to reduce or remove the distortion.
R.Harpst
23rd of December 2006 (Sat), 01:24
Thanks for the help..I see what your saying...
JimHejl
23rd of December 2006 (Sat), 09:45
Nice pic though
(of all things, I am in Houston today also)
R.Harpst
23rd of December 2006 (Sat), 12:22
Nice pic though
(of all things, I am in Houston today also)

Thanks and welcome to our little city...
D. Craig Flory
23rd of December 2006 (Sat), 14:17
You discovered why commercial photographers used view cameras for so long ... and why a lot still do with a digital back. You have swings and tilts along with a rising and falling front to control distortions.

They are expensive but there are distortion control lense made.
Terrywoodenpic
23rd of December 2006 (Sat), 14:37
Even when you bring verticals vertical if often looks a bit wrong, but it is the best you can do when both ends go out of the picture.
Tower blocks and the like often look better left slightly tapered.

http://xs210.xs.to/xs210/06516/church2.jpg