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Fixing perspective/distortion

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  #1  
Old 05-01-2010, 07:56 AM
ziggy25 ziggy25 is offline
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Fixing perspective/distortion

I am trying to learn how to fix a distorted picture in CS4 but cant seem to get it right.

The main problem i think i have is im not sure exactly how to fix the distortion. I usually use one of two options in CS4. Either rotating the picture or using the "Distortion" options under the "Filter" menu.

The problem with rotating the image is that it messes up other areas of the image which are perfectly straight. Take this image for example, if i rotate it, the taller structure does straighten but the ground becomes tilted and the other structure on the left also becomes tilted.

http://farm5.static.flickr.com/4072/...fa3f6c8e_o.jpg

The option in the "Filter>Distort" menu looks quite usefull but i cant really work out how to use it correctly. I usually use the first option which is for distortion. When i try it, can never get it to straighten the image. Here is another example,

http://farm3.static.flickr.com/2080/...00e06c46_o.jpg

The minarets are not straight at all. If i try the distort option in photoshop i find that anything above +3 make the image look slightly weird. The problem is that at +3 the minarets are nowhere near straight.

So how can i fix distortion in my images? I have tried my best to keep the horizontal straight when i take the picture but they always appear distorted. This seems to be worse when i use a wide focal length i.e. 17mm to 20mm.
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Old 05-01-2010, 09:07 AM
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Juergen D Juergen D is offline
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Re: Fixing perspective/distortion

I used the Lens Correction filter and set the Vertical Perspective to -54. The only other correction was via Skew, pulling the lower left corner out just slightly. Of course some of the real estate is being lost due to the necessary cropping.

Juergen
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File Type: jpg Perspective.jpg (195.8 KB, 38 views)
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Old 05-01-2010, 09:50 AM
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Re: Fixing perspective/distortion

Just a very quick try at this:
1st version landscape using Distort/LensCorrection/ adjusting vertical and horizontal.

2nd version using Edit/Transform/Warp - left border as is to show degree of warping.

3rd Picture. Corrected path (pos barrel distortion?) and then used Edit/Transform/Warp again.

As pointed out above you will loose some image real estate - but if it is important you may consider cloning missing detail

I am sure that you will be able to do a much better job than shown here with a little time and patience.
Attached Images
File Type: jpg Lens-filter-correction.jpg (33.8 KB, 21 views)
File Type: jpg Transform-Warp.jpg (44.6 KB, 22 views)
File Type: jpg LensBarrelTransformWarp.jpg (95.5 KB, 35 views)
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Old 05-01-2010, 10:29 AM
ziggy25 ziggy25 is offline
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Re: Fixing perspective/distortion

Thanks guys for your responses. I think the mistake i have been making (being new to photoshop) is that i was only using the "remove distortion" option under the "Filter>distort>lens correction" menu.

I didnt realise that i also need to try out the vertical and horizontal adjustments. I will play around with these (including Edit/Transform) this evening and see how it goes. Judging from what you guys have done in your quick tries i think they can be fixed if more time is spent on it.

Thanks
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Old 05-02-2010, 05:24 AM
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Re: Fixing perspective/distortion

I still think all you need is the lens correction filter, but you need to use all it's options, not only the barrel distortion corrections, but also the perspective correction. If your glass distorts in a way that you have to use the warp tool, then there's something wrong with it.
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Old 05-02-2010, 05:47 AM
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Re: Fixing perspective/distortion

Quote:
Originally Posted by flexmanta View Post
...If your glass distorts in a way that you have to use the warp tool, then there's something wrong with it.
I agree with you here. The warp tool solution only offered as a possible way to keep more of the original image after cropping
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Old 05-02-2010, 06:04 AM
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Re: Fixing perspective/distortion

Fair enough..
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Old 05-02-2010, 09:47 AM
secretagents secretagents is offline
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Re: Fixing perspective/distortion

Don't forget you've got selection tools well suited for doing that as well.

With Photoshop 7 and selection tool enabled on the tool palette: Select all -> Right click on selection -> Free Transform -> Right click again -> Perspective.
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File Type: jpg Untitled-2.JPG (88.4 KB, 9 views)
File Type: jpg Untitled-1.JPG (95.6 KB, 9 views)
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Old 05-02-2010, 11:28 AM
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Re: Fixing perspective/distortion

secretagents, the barrel distortion of uncorrected wide lenses cannot be corrected with that.
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  #10  
Old 05-02-2010, 12:39 PM
secretagents secretagents is offline
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Re: Fixing perspective/distortion

You're certainly right about that flexmanta but what I am seeing is that the above corrections made with the lens filter seem to suffer from almost exactly the same as you show on mine so I am thinking that there is very little barrel distortion issue in this pic.
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