Briser
newbie
Reged: 06/07/2008
Posts: 40
Loc: Fraserburgh, Scotland
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I have a habit of taking a pic and not paying full attention to lining up the horizon 
- I have PSP8, how can I use this to straighten out my pics?
thanks!
BTW, here is a typical example 
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- Briser's Flickr Fotos -
Edited by Briser (08/07/2008 23:02)
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1182
Loc: Buckinghamshire and Cumbria
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Three ways come to mind. The first is to get it straight to start with. That's not much help and is actually easier said than done. The Nikon D3 has a built in horizon so even the pros need help so you shouldn't feel too bad about it.
Method two is simply to rotate the picture then crop out the useful rectangle. The third is to use the perspective control. This is a very useful control that can be used to correct verticals on buildings. You'll need to play about with it as you will need to keep the sides and top square and straight and just adjust the bottom line.
Any other ideas folks?
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Stevet
Reged: 12/06/2003
Posts: 601
Loc: Lytham
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I use Photoshop, but hopefully PSP can do what is required. In addition to the 'sloping horizon' The image has pronounced barrel distortion and also 'keystoning' (the latter due to camera beng tilted up).
I corrected the slope (you can use 'rotate image' or do it in the lens distortion filter), then corrected the barrel distortion (lens distortion filter) then adjusted the keystoning to get the vertical alignment correct(edit, transform, perspective). finally cropped image as all that transformation resulted in a less than rectangular image area.
I did this quickly, obviously with a small file (still not sure the verticals are!), but here goes...
Edited by Stevet (09/07/2008 14:21)
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1182
Loc: Buckinghamshire and Cumbria
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Yes, correcting the barrelling is a significant improvement.
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Briser
newbie
Reged: 06/07/2008
Posts: 40
Loc: Fraserburgh, Scotland
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Thanks everyone - its an old photo I took some years ago with a budget HP Photosmart M407 but I always liked the colours. never considered fixing it until I looked at it recently.
PS - how can you tell it suffers from barelling? 
Edited by Briser (09/07/2008 18:37)
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Stevet
Reged: 12/06/2003
Posts: 601
Loc: Lytham
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Quote:
how can you tell it suffers from barelling?
If you rotate the image to try to get a 'flat' horizon you will see that the horizon is curved - in this case as it is towards the bottom of the frame and curving down in the middle there is barrel distortion. If the curve was upwards it would have pincushion distortion.
HTH.
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Steve Thompson FRIPN
Benches - for togs who really know where their towel is.
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Briser
newbie
Reged: 06/07/2008
Posts: 40
Loc: Fraserburgh, Scotland
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Thanks Steve, I understand now.
Can someone explain "Keystoning" please (last question I promise!).
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- Briser's Flickr Fotos -
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Stevet
Reged: 12/06/2003
Posts: 601
Loc: Lytham
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Here Goes:
If you point your camera at something with distinct verticals (e.g. a tower block) and keep the focal plane vertical (i.e. don't point the camera up or down) the sides of verticals will 'stay' parallel.
Now incline the camera upwards (like you did in your image ) the vertical features will appear to lean together as they go from bottom to top. Incline the camera downwards and the opposite happens, they appear to lean together from top to bottom.
Think of the shape of a keystone in a stone archway to see where the terminology comes from, and given your IT background, the shape of a projected screen if you raise the front of a projector (if it doesn't have automatic keystoning rectification.)
HTH
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Steve Thompson FRIPN
Benches - for togs who really know where their towel is.
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Briser
newbie
Reged: 06/07/2008
Posts: 40
Loc: Fraserburgh, Scotland
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Got you now. Thanks Steve.
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- Briser's Flickr Fotos -
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