Unusual perspective problem

[amtb]

This is a problem I have not met before and so far I haven't found an answer.

The shot was taken on the down escalator of a London department store. I wasn't too careful with it and thought it would not be very difficult to correct the perspective so that it looked as if it had been taken half way down and with no camera tilt. In other words, it would be symmetrical. about the vertical mid line. The problem is with the curves of the balconies, transforms all seem to distort them so they are not symmetrical. I'd be glad to know of a technique - or is it impossible, even with the Photoshop CS arsenal?

JohnF

[Gary Richardson]

Hi John, not sure exactly what you're looking for, but had a go with free transform tool and got this.

[Janet Petty]

I'm like Gary, I'm not exactly sure what you are looking for. But I do know one thing. Whatever crop you choose, you will lose some of your picture. I tried to minimize what was lost. I'm not sure I was successful.

There are several ways of cropping a picture such as yours. Gary's was very well done and probably better than the one I'm posting. He used transform. I went another route and used the measure tool (hidden under the color eye dropper), measured a straight line, then went to image>rotate>arbitrary. With the measure tool selected, the arbitrary setting automatically puts in the amount of rotation you need to straighten your photo. Once that is put into effect, you can crop your picture.

And speaking of crop...were you aware of the perspective setting on the crop tool? I tried it on this picture and ended up with a straightened version, but one that I didn't feel was acceptable. You might try it and find differently though,

Good photo if you don't suffer from vertigo. Enjoy.

Janet

[Chip Hildreth]

I don't think you can make this one work out to a true flat perspective because the camera was both tilted and away from the midpoint. If you had one or the other you could use a vertical or horizontal line as a reference and correct it. Correcting convergence in Photoshop is useful and can make the difference between a snapshot and a sellable image but the original needs to be close to straight begin with.

With that said, I think this is a valuable picture that doesn't need architecturally accurate perspective. To me, it conveys a feeling of light and spacial depth as it is. I think I would just straighten it a little something like Gary did and let the convergence do it's thing. The exposure is really pretty awsome, doesn't look handheld to me... nice.

Big interiors are pretty hard to get right even with a view camera and a perfect vantage point; not because you can't eliminate convergence but because you usually have to use a wide angle lens and the parallel lines will emphasize even a small amount of barrel distortion... you can't win. Try shooting from an off-center location, even a corner; you can correct the verticals and forget about horizontals because they will all be oblique, the barrel distortion will be less apparent because it affects a non-symmetrical field.

Convergence can be a good friend, particularly on the horizontal axis because it conveys depth and scale.

Chip

[amtb]

Thanks folks. It all tends to confirm my impression that one can correct straight lines without too much difficulty but curves are probably impossible to keep undistorted when correcting perspective. Next time I want to do something like that I will be a lot more careful how I go about it.

JohnF

[roger_ele]

This is my free tranform version without cropping (in order to see what was done), just done by eye to balance the lines and the shapes. The empty areas could be filled in from sections of the other side if you did not want to crop anything.

Roger

[philbach]

John I took a look at your picture and submissions by the other members. From my "pespective" the major problem is that you were not in the middle of the Arch when you took the picture. If you want to make it very symmetrical moving a little to the left and retaking the picture would help.