thinking outside the box

Photo Editing - a 'real-world' example


Perspective Correction

The first step is to fix the perspective problem. Xara has a totally automatic ‘perspective correction’ facility that can fix the leaning building syndrome that you get with wide angle shots. Just select the photo then select the perspective correction tool from the fly-out menu of the Photo tool: After a few seconds you get back the corrected version: This process will often change the size of the image slightly, but you can resize it as required using the Selector tool. Tip: This operation creates a new image which is a ‘raw bitmap’ and not a JPG, and so it will take a lot more memory and slow down save operations. You can optimize this image to be a JPG.  Just select the image, and then the menu Utilities > Optimize Photo… Now that the building is upright, the most obvious problem is that it’s badly composed with far too much sky. In fact, this is the most likely reason that it’s so badly under-exposed as most of the photo is sky containing some bright clouds.


So I want to crop some of the sky out of the picture. The easiest way to crop when in the Photo Enhance tool  is to just drag the top-edge round handle down. This is a better composition with less sky and more of the building.  But it’s too dull as a result of underexposure.


We can correct the exposure and lighten the building using a variety of the Enhance tool options. The Histogram tool in the Brightness Levels Dialog is the best way to get an overview of the brightness levels of an image. See our tutorial about the Histogram tool. The histogram of this image shows why it’s so dull. The image is composed of mostly dark to medium brightness. There’s almost no light pixels in the image - as shown by the absence of anything at the right end (the light shades) of the above histogram. So instead of an even spread of shades, dark-to-light, most of the light end is missing. To correct cases like this drag the White Point control (shown above) to the end of the red. This will now re-distribute the shades over the whole range. With the adjusted White Point, the histogram now shows the range of shades spread more evenly over the whole range (the pale red chart is the adjusted histogram, the dark red is the original), and you can see the image is now brighter, particularly the sky.  But the parliament building is still too dark. So we can use the various brightness controls to adjust this. The best way to do this is by eye. Select the ‘Enhance photos’ tool again. I could use just the Brightness control, and although this does put more emphasis on brightening mid to dark shades, it still makes the image look a bit too washed out if I use this alone. Using the Shadows Brightness control is better as this only affects the mid-to-dark shades, without touching the brighter shades at all. The following version has a small brightness change of +7 and a Shadows Brightness value of +59. The building is much brighter. The Histogram shows the change - if you compare it with the previous, the pale red chart is the same at the bright (right) end, but the darker shades have been moved to the right. The overall brightness balance visually looks better, and the histogram now shows a much better balance across the chart then before. Here’s a before and after of an enlarged part of the image showing the image is straighter and brighter.     Click to enlarge You might notice one other difference - some of the people and cars are missing from the ‘after’ version so next I will show you how I removed them.  
Perspective Correction
Drag this White Point control to the end of the red.