Perspective Correction in Photoshop 7

I kept an article in Popular Photography (can I admit that I read that?) on how to do perspective correction in Photoshop. I kept it in such a special place that I can't find it. Also checked Scott Kelby's book and can't find anything there. Anyone familiar with this?

I want to straighten out the building in this shot so it doesn't look like it's falling over - I shot it on medium format with a 50mm (wide angle) lens pointing up a few degrees, planning to do this technique later (or much later as you can tell). Thanks in advance.

Is this the article Steve?

http://www.popphoto.com/article.asp?...&page_number=1

And the word of the day is "Duh!". Thanks - didn't think about checking their website.

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Originally Posted by another view

And the word of the day is "Duh!". Thanks - didn't think about checking their website.

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Is the word of the day like the secret word on Pee Wee?

Well, Seb - you know where those secret words got PeeWee...

So after a couple minutes in Photoshop, here's the new version. Original is on Kodak E100VS, scanned by a lab. Obviously taken July 4th last year - 8 hours later we would all be standing out in the street looking at the damage that 100+ mile winds had just caused. We didn't have power at our house until 4-1/2 days later.

You know, after all that went down I felt justified for hating Pee Wee as a child, when all the other kids were SOOOOO into him.

Anyway, the second one has less lean, but lean is still there. When using the crop tool to adjust perspective, move the cropping marquee parallel to the edge of the building, then pull it back out to the edge of the image. PS will automagically keep the right angles to make those edges straight. Otherwise it's sort of guess and pray to get the edges lined up with the images.

I'm going to send you down a long and dangerous path but here goes....

There are actually some horribly complex, but sophistaced and powerful freeware tools out there that I've used to help with panoramic stitching that help with this as well as barrel and pic-cushion distortion.

So rather than point you directly to the tools which I haven't used in a long time....I suggest that you can start looking at panoramic tools that digital photorgaphers use. What's cool about these tools is that you can actually characterise your lenses and script the corrections in the future. Here are a few links to get you started:

http://www.culture.com.au/virtual/tutorials/calib.htm
http://www.all-in-one.ee/~dersch/

BTW, the photoshop tools that are built in aren't good enough for highly accurate corrections. The reason for this is that at wide angles (where we're often concerned about these things) the distortion is of a spherical nature. This means that (depending on the subject to camera distance) the distortion is usually much more prounced on the edges of the frame than in the center. Also, the amount of distortion varies from the center going to the edge. This means that applying "one" correction using something like the perspectice tool in photoshop will always be a compromise to get the best overall. Use of tools like I mentioned before have algorithms that will do better. Just how much work do you want to spend eh? :)

Thanks Seb and Trevor - I'll have to try those programs. I didn't get all of the perspective distortion out of the shot for two reasons - I think it looks a little more natural to have some of it in there, and definately better than pulling it too far the other way! Further checking in Scott Kelby's book shows that he does have it, he just calls it Keystoning.