Photoshop Tutorial - Straighten Your Horizons - Lens Corrections - Pincushion and Barrel Distortion
Today's Photoshop Tutorial is about lens correction. When we take a photograph, lines that appeared straight enough while looking through the lens seem tilted and/or curved when we look at the actual photograph.
To straighten these lines in Photoshop, in this case a tilted, curved horizon, click on "Filter", "Distort", and "Lens Correction". The "Lens Correction" window appears with a variety of tools for helping you correct for aberrations introduced by you or your lens.
Make sure that "Preview" is selected, or you will not be able to see the effect of the various tools on your photo.
I keep "Show Grid" selected, as the lines really help to determine what needs fixing and by how much.
If the grid blends in too much with areas of your image, you can change the colour with the "Color:" selector.
The first thing I like to fix is the angle. You can see here that one end of the horizon is higher than the other. If we make them even, then the "Remove Distortion" tool will work as expected relative to the grid.
For a nice, fine tune of the angle, click over the word "Angle" and drag to the left or right. Use the grid to help you align. You can also use the angle wheel or type in an exact degree value.
There are two basic types of linear distortion. When the lines curve inward like this horizon, it is a pincushion distortion. When the lines curve outward it is a barrel distortion. Pincushioning is usually associated with telephoto lenses, and barrelling is associated with fisheye lenses.
Move the "Remove Distortion" tool slider to the left to correct for pincushion distortion, or to the right to correct for barrel distortion, or type negative or positive values, respectively, to the right. As with the Angle and other tools, you can fine tune by dragging left to right over the tool name.
If your lens has darkened the corners of your photo, you can use the "Vignette" tool to lighten them. We don't have that effect in this photo, so I'll keep this at "0".
Depending on your subject matter, and particularly with photographs of architecture, you may find that you need to adjust your vertical and/or horizontal perspective to straighten things out.
Finally, you will notice that our adjustments have created transparent areas around the edge of the image. To keep the maximum data from your original photo, you can keep this edge "Transparent", or use the "Edge Extension" option to blend out to the current edge, or fill with the "Background Color". Edge extension works best with flat colours. I typically use the scale tool at the bottom of the "Lens Correction" filter window to expand the image until the transparent areas are pushed outside of the image frame. I lose a little bit of data from the edge of the original photograph, but it is more than made up for by the adjustments I have made.
To compare the adjusted image with the original, uncheck the "Show Grid" option and toggle the "Preview" option. You can easily compare versions and appreciate the power of the "Lens Correction" filter. The preview is not as sharp as the original, but you'll notice when we select "OK" and apply the filter, that it sharpens up again.
Click "OK" when you are happy with the results.
I hope that this Photoshop Tutorial has been helpful to you.
If you have the time, please take a moment to rate this Photoshop Tutorial and to send me some feedback.
