I took this photo of Notre Dame Cathedral a week ago when in Paris and was fairly close to the building. I shoot a Canon T3i with a Tamron 18-270 lens. The lens was set at 18mm, f/9, ISO100. The architecture is noticeably curved up on the left - which is not reality of course. When I stepped further away, the shot straightened out - well sort of (see shot #2). Just wondering what caused this. Is it a limitation with the lens at this short of a focal length? Advice and feedback appreciated!

I took this photo of Notre Dame Cathedral a week ago when in Paris and was fairly close to the building. I shoot a Canon T3i with a Tamron 18-270 lens. The lens was set at 18mm, f/9, ISO100. The architecture is noticeably curved up on the left - which is not reality of course. When I stepped further away, the shot straightened out - well sort of (see shot #2). Just wondering what caused this. Is it a limitation with the lens at this short of a focal length? Advice and feedback appreciated!

The lens correction filter in Photoshop works fine if you know you're trying to correct a vertical edge. But a few weeks ago I tried correcting the Leaning Tower of Pisa -- and could not figure out how much to correct!

The original image (camera pointing up, of course) made the tower leaning IN, whereas it was actually leaning OUT. If I had been post processing on site it would been ok, but at home I could not get a clue since there was nothing vertical in the background near the tower.

Any ideas? Before and after images follow.

Having always been involved in photographing buildings of all shapes and sizes over the years it has always been a source of irritation that most every photograph I have seen of tourist attractions of such buildings as the Notre Dame Cathedral most often look like the builder did not possess a level and a plumb line.
Professional Architectural photographers would use a view camera with movements to correct the distortion with a control called a rising front . If you are undertaking a lot of photographs of buildings you can help overcome the problem by moving further away from the subject so that the camera can remain in a horizontal position. If you are well healed you can invest in a special wide angle "Tilt / shift " lens that allows you to move the lens upwards in relation to the film plane.
You can achieve a similar effect in the computer (I can only vouch for this correction in Corel Paint Shop Pro, since it is the only program I own, Its called, would you believe "Perspective" control. And takes maybe 20 seconds to achieve.

The correction however somewhat distorts the image a little in other ways and chops a small amount off the edges of the photograph.

I took the liberty of correcting both images and you can see the images that resulted. Its a kind of result of compromise which distortion do you prefer! Bottom line, put up with the distortion, stand further away so you avoid tilting the camera, buy an ultra wide angle lens and crop out the subject from the center of the photograph, buy my Sinar (best route) or a wide angle lens with tilt/ shift facility!

You "pays yer money and makes your choice!

Ian

You can do a pretty good job of it in Photoshops Lens Correction -
The key is that before you apply the keystoning correction, you have to get the center of the image straight. Look at the brick buildings in the background - the buildings are tilted to the left at the image's vertical center line. Once you have rotated the image clockwise to get those buildings straight up and down at the centerline, Use the Vertical Perspective control in the Transform section (under the Custom Tab) to straighten up the verticals in the building on the left (I am assuming that that building wasn't leaning). Now the tower will lean to the right approximately as it should be without looking like it is actually falling over! I might have been a little too conservative when rotating the image initially, so the tower might really be leaning to the right a little more!

Harry

You can do a pretty good job of it in Photoshops Lens Correction -
The key is that before you apply the keystoning correction, you have to get the center of the image straight. Look at the brick buildings in the background - the buildings are tilted to the left at the image's vertical center line. Once you have rotated the image clockwise to get those buildings straight up and down at the centerline, Use the Vertical Perspective control in the Transform section (under the Custom Tab) to straighten up the verticals in the building on the left (I am assuming that that building wasn't leaning). Now the tower will lean to the right approximately as it should be without looking like it is actually falling over! I might have been a little too conservative when rotating the image initially, so the tower might really be leaning to the right a little more!

Harry