So, sometimes your straight lines don't appear totally straight in your photos. Sometimes they lean inwards, or outwards, or sideways, whatever. Your eyes are so smart, they can make these corrections automatically, and a PERFECT lens, would make straight lines straight. However, most practical lenses aren't PERFECT, so you get some funky distortions. The wider your lens, the more distorted your images become (which is why fish-eye lenses make those fun images!).
We are going to look at a super simple way to correct distortions like this in Photoshop Elements (it works almost the same way in Photoshop, just a little EASIER!) using guides and the Free Transform tool.
1. Open an image that is supposed to be straight, but maybe isn't completely. I am using a fun shot my husband took in our downtown area with my point and shoot camera. I haven't done ANY editing to this shot - what you see is what you get. You might notice in this shot how the vertical lines running up the building are leaning slightly to the left instead of straight.
2. The next thing to do is to create a duplicate layer of your background. You can do this by clicking on Layer>Duplicate Layer or simply click on your background layer in your layers palette (to the lower right of the screen) and drag (holding the mouse button down) to the little dog-eared square and release your mouse. That will create a duplicate background. You should now have 2 layers that are exactly the same. We'll be working on this background copy so you can see the before and afters easily.
4. With your rulers out, if you are using Photoshop 7, or CS or higher, you can simply click on one of the rulers and drag down or across to create little lines that will act as guides. They will be straight, and will act as a guide for when we transform our image. Elements doesn't support guidelines, so we'll create our own in this next step. Create a new layer above your background layer, by clicking on "Layer>New>Layer" or just click on the "new layer" icon above your layer palette (that same dog-eared square). Now you'll have a blank layer to create some guide lines on, without permanently putting those lines on your image.
6. To create our own guides, we will choose the pencil tool from our tools palette. When you click on it, you can adjust how big a line you want it to make. I chose 10 px for this example. You can also set your foreground color to whatever color you want your line to draw in at. It doesn't really matter what color you use except that you want it to show up well on your image.
7. Now you will click somewhere at the top of your image, somewhere close to the spot you want to make straight. I chose a spot close to the vertical line running up the building. So, you click, then WHILE HOLDING DOWN THE SHIFT KEY, drag your mouse down until you reach the bottom of your image, then let go. Holding the shift key will make the line completely straight. You can do the same for a horizontal guide. You can do this in as many spots you want to act as a guide for when we transform the image.
8.Click on "Free Transform" by either clicking "Ctrl+T" or clicking on "Image>Transform>Free Transform". This will create a little outline around your image with little boxes at each corner. You've seen this before, I'm sure. But DON'T start dragging the corners - that will only drag the ENTIRE photo larger or smaller. No, we will be doing it a little differently :)
9. While holding down the "Ctrl" key (Command on a Mac), click on one of the corners and drag. You will have much more control this way. Drag the corners, one at a time, until you're photo lines up with your guidelines. You can see I only did a slight adjustment on this image. Click "Enter" or click on the little checkmark sign when you're happy with the changes.
10. Isn't this totally fun? You can see the before and after by clicking the little eye toggle on and off of your background copy layer. You can see my before and afters here: