Straightening Curvature in a panoramic shot
I stitched 5 shots of the Teton Mountain Range (Wyoming) into a panorama using Photoshop. The final product looks pretty good EXCEPT for a slight curvature (?of the earth) towards the center. I've tried the ruler tool in PS, but can't seem to flatten it. I would be grateful for any suggestions (...and no, I do not believe that the earth is flat!)
#1. "RE: Straightening Curvature in a panoramic shot" | In response to Reply # 0Antero52 Nikonian since 07th Jul 2009Thu 25-Oct-12 06:11 PM
- have CS6,
- used CS6 to stitch the panorama,
- and CS6 has an automatic lens correction profile for your lens,
then the best tool is the Adaptive Wide Angle filter. Select the ruler tool, and with the shift held down, draw one horizontal line and zero or more vertical lines, along features that you know to be horizontal or vertical.
#3. "RE: Straightening Curvature in a panoramic shot" | In response to Reply # 2Antero52 Nikonian since 07th Jul 2009Fri 26-Oct-12 04:44 AM
In CS5 probably the best tool is Edit / Transform /Warp. Before using it, zoom out the picture so that it fills less than your complete work space. That way, you have room for the adjustment handles later on.
Copy your layer. Convert it to a smart object (right-click on layer). Use Edit / Transform /Warp. You image is overlaid with a grid, with handles in the corners. Move the corners in or out as required and use the corner handles to get your horizon, or whatever line, straight. When it looks good, confirm with Enter. If you're not satisfied, do another Warp, and a third, until it looks good. When you're completely satisfied, Rasterize the layer (convert the Smart Object back to a normal pixel layer, use right-click again).
The excursion to Smart Object has the benefit that you can perform multiple Warps and other distortions without degrading image quality. All the geometric transformations are combined in the geometry domain and the pixels are shifted just once. Without the Smart Object conversion, each time you confirm a transformation with Enter, the pixels are recalculated by combining information from neighbor pixels, which obviously blurs the image. In the Smart Object route, this blurring is done only once and minimal resharpening is required.
And you can download a 30-day trial version of CS6.
One more tip. Before doing the transformations, its' a good idea to add an extra layer and draw a horizontal line on it. For instance, use the marquee select to create a thin horizontal selection and fill it with a color that contrast with your image layer. Move that layer to where your horizon should be. Or, if you're comfortable with shape layers and vector tools, just draw a vector line on the extra layer.