Photo correction
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This page about photo correction deals with geometrical corrections i.e.
sloped axis corrections and barrel or pincushion corrections.
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Axis photo correction (horizon)
Ever took a photo where the horizon is not horizontal?
Of course, we all do!
Photo correction of a sloped horizon is easy, all you need is to be able to rotate your photo.
Not 90° or 180°, but 1°
-even 1.5°- 2° or whatever will fit.
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Not all programs accept decimal values for the rotation angle!
And most important, the rotating function must offer the antialiasing feature.
Without antialiasing, the result after rotating your photo by a small angle will be full of ugly steps.
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With common photo editors you have to type in the angle of rotation you wish to apply.
You will probably have to try a few times forth and back before finding the exact angle it needs to put your horizon back to horizontal.
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With Zoner Photo Studio
you would just draw a virtual line over the horizon with your mouse
to tell that this is what you want to be horizontal and the program knows (calculates) how much to rotate your photo.
A very convenient and fast way to do the photo correction of sloped horizon lines.
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Zoner Photo Studio is more convenient.
The photo correction function for slanted horizon lines is directly accessible via a button in the tool bar.
With Photo-Brush it is accessible via a sub menu (I hate sub-menus because they like to flip away).
Photo-Brush has a similar function to correct vertical axes too.
Zoner Photo Studio doesn't have it, but it has another direct button to correct a vertical colinearity problem.
After rotating an image by a small angle, empty slanted edges will appear of course.
An important advantage of Zoner Photo Studio is that it will automatically crop your image after the rotation (if you select it)
to eliminate these empty slanted edges.
With other tools, you will have to crop it manually afterwards.
I did save a lot of time by using Zoner Photo Studio for photo correction of slanted horizon lines
and not having to crop the image separately after the small rotation.
Barrel and pincushion corrections
Barrel and pincushion effects often occur when you are using a "cheap" zoom objective at its extremes.
Either at its maximal tele position or at its minimal wide angle position.
The effect is particularly visible when you take pictures with distinct horizon lines
(e.g. on sea) that are situated near the upper or lower border of the photo.
The horizon line is then curved instead of being straight.
This kind of photos need a geometrical photo correction to render the horizon line straight again.
Zoner Photo Studio
has a very convenient tool for barrel and pincushion photo corrections.
After applying a barrel or pincushion photo correction, the edges of the photo will be curved,
either convex or concave.
Like above, an important advantage of Zoner Photo Studio is that it will automatically
crop your image after the geometrical photo correction (if you select it)
to eliminate the curved edges.
PR Lens corrector
is photoshop plugin specially aimed to correct barrel and pincushion distortions.
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Plugins are a kind of additional tools that you can add to a basic package (software).
Photoshop plugins do not only work with Photoshop and Photoshop Elements,
but also with image editors like Paint Shop Pro, Photo Brush and many others.
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PR Lens corrector's advantage is that it allows you to perform asymmetrical photo corrections.
You may want to apply a barrel correction only horizontally, but not vertically,
or with a higher factor on the upper edge than on the lower edge.
With this plugin it is possible.
