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Sunday, September 1, 2013

Architecture - 2


Correcting Perspective Distortion

Objects that are farther away will appear smaller – to your eye as well as to your camera. When you look up at a building the top part is bound to look smaller. Our brain intercedes and makes the needed interpretations so we are not bothered by the optical effect that we call “perspective distortion” in real life. However, when we see the same thing in a flat photograph it looks like the buildings are falling in on each other.

Here is an example of such a situation:

Atlanta Skyline

This is how the camera say it, and this is how the photographer saw it, but it just didn’t appear that way. What I thought I saw when I took the picture was more like this:

Atlanta Skyline

Quite a bit different, and much more realistic. If the camera is tilted upward when a photo is taken, the top of buildings will be imaged smaller because those parts are farther away from the camera than the bottom parts of the building. This photo also shows a gate structure, one end is closer to the camera and the other farther away. We see the same effect, but this seems much more natural because we are used to seeing the world this way all the time. It is mostly the vertical perspective distortion in photos that bothers us.

In this article I will show you how you can easily make corrections to your photos so they look real and impressive, maybe even really impressive!

Most of my readers know that my “go-to” application for managing and improving photos is Windows Photo Gallery. I am biased, I admit, I wrote a couple of books about this tool. Photo Gallery is aimed at the casual photographer and not intended as a full-fledged photo editor. It does not provide a tool for perspective correction. There is a Microsoft tool, another favorite of mine, Image Composite Editor, I like to call it ICE, that can do a very nice job of making such corrections. It is a “photo stitcher” by design and normally is used to combine a number of photos into a composite such as a panorama. It does not work with just one photo.

For just making perspective distortion correction we need to trick ICE into thinking that it is working with two photos.

Here is the procedure, the video here shows the steps but without sound or explanation.

Since ICE can be called directly from Photo Gallery, that is the way to get started. Make a copy of the photo. In Photo Gallery there are tools for that, but I like to just right-click a photo, select Copy, then right-click an empty space and select Paste.

Next select both photos: Click on the first one, then hold down Ctrl and click the copy.

Demo of ICE for making perspective distortion correction

Click the Create tab, click More tools and under Microsoft Image Compose Editor click Create image composite.

(If you do not have ICE installed on your computer you need to do that first, ICE is free and still available from Microsoft: Image Composite Editor Download).

ICE will load the two images, since they are identical the “composite” you see is just the photo.

imageOn the left side in the Stitch panel click the selection button and click Rotating Motion.

Next click the little box in the tool bar at the top.


ICE will already have selected Perspective as the projection to use, but you can make sure by clicking Projection.

Now you can drag the photo right and left for horizontal perspective adjustments and up and down for vertical perspective adjustments. Start near the center and note the custom pointer with horizontal or vertical pointing arrowheads. You can combine the vertical and horizontal corrections. Move the pointer to the bottom of the image and you will be able to rotate it as well.

This is much more easily demonstrated than explained in text. So take a look at the video. Click the ► play button, you can select a higher video quality and view it full screen so you can see the details better.

Now is that not an impressive way to make perspective corrections?

I like to leave just a little bit of “lean” to the buildings, that seems more natural in the final image than perfect correction.

When you have made the correction as you like it, click the Apply button. ICE will now show the corrected image with a cropping frame around it. You can do the cropping right in ICE. You can select the final JPG image quality or select another file format. To save the image to your computer click the Export to disk button. (Yes, there are other options but not for today.)

After you have used ICE to make perspective distortion corrections you will come to prefer this method to the tools that the full-fledged photo editors provide.

If you have trouble with the video above, use this link: