Correcting Horizon and verticals

Two of the commonest faults with photographs are horizontals that aren't horizontal and verticals that aren't vertical or a combination of both and yet, with Photoshop, they are very easily corrected.

One of the decisions that has to be made when correcting for these problems is what part of the image should be vertical/horizontal and that is probably the hardest part of the task! However, I have yet to find an image that this technique cannot be applied to with a touch of ingenuity.

My thanks to Chris Mayers who has kindly agreed to let me use his excellent image for this tutorial as it will clearly demonstrate the different elements used, so less of the notion and more of the motion.

1. Open the image in Photoshop

2. Select the Ruler tool from the tool bar

3. Notice the cross-hairs of the tool - position the cross-hair at the extreme left of the sea/sky horizon A then click and drag the cross hair to the extreme right of the sea/sky horizon B then release the mouse button.

4. From the Image > Rotate Canvas menu choose Arbitrary. Notice that Photoshop has calculated correct amount based on your selection - press OK to rotate the canvas and straighten the horizon.

5. Use the Crop tool to square up the image

6. Now do Ctrl A to select the image followed by Ctrl - (hyphen) to give some clear space round the image. Click and hold on each side of the image and drag outwards to give a bit more space around.

7. Now do Ctrl T to switch on the Transform tool. Right click in the image and select Skew from the options. Click and hold on the bottom corners of the image in turn and drag outwards to straighten the verticals of the two near-most columns. It will take a     few minutes alternating between the two until you get them both vertical when compared to the frame edge. When you are satisfied hit the Return key to apply the transformation. Do Ctrl D to clear the selection.

Here are the 'Before' and 'After' versions.

You will notice that all the above images display the top and left hand ruler bars; please do not confuse the Ruler Tool described in the text with these ruler bars.

For those who don't know, by positioning the cursor over the ruler bar and holding down the left mouser button, a guide can be dragged across the image to check for vertical or horizontal components as appropriate. The guide can either be dropped on the image by releasing the button, or returned to the menu bar. Guides that have been 'dropped' can be moved by using the Move tool. A much less cluttered method than using Photoshop's grid in my opinion.

Siversnapper. (Keith)