Correcting keystoning

In the photograph of the same church below, I corrected the distortion in Photoshop. If you use a perspective control lens, which is specifically designed to correct keystoning in-camera, post-processing isn’t necessary to address this issue. Most photographers don’t carry such a lens because they are expensive and heavy, so here are the steps required to make the vertical lines vertical in Photoshop:

1. Open the image to be corrected and choose

Select > all.

2. Choose the pulldown menu command Edit

> transform > distort.

3. Grab the lower right or lower left corner of the image and pull it to enlarge the working area. See the screen capture on the next page. The green arrow shows the place where you can drag to expand the area around the photograph. Once expanded, a black frame will surround the image.

4. Immediately around the picture area itself is a box with handles. This was created from performing Step 2. The handles are shown by the blue arrows, same screen capture. When you pull the top left handle to the left and the top right handle to the right, the vertical lines of the subject which were originally skewed inward now become straightened.

As you can see from the screen capture, the handles don’t have to be pulled symmetrically. In fact, in most cases they will appear asymmetrical as you work to align the vertical lines with the left and right sides of the picture frame.

The reason I expand the working area as previously described is so I can see the handles and, if necessary, grab them again to make small adjustments in aligning the vertical lines in the photograph.

5. Things to note during this process:

a. Depending on where you have to drag the handles, you may end up with a blank area in a portion of the picture. This is indicated by the red arrow, below. If this happens, simply use content-aware to fill in that area. Alternatively, you could use the clone tool.

b. In distorting the image to correct the keystoning, the subject may appear to be flattened somewhat. If this occurs, simply grab the top middle handle and pull it up until the photograph is stretched back into the correct proc. You will lose some of the picture area along the right and left sides of the frame as you straighten the vertical lines. This is unavoidable. Therefore, if you know you’ll want to use this technique, plan ahead. Compose the picture with area on the sides of the frame that won’t present a problem if they are eliminated from the composition.

For example, the photo of The Bean in Chicago on the next page shows how I corrected the keystoning but, as you can see, some of the buildings at the far right and far left were cropped out. I didn’t crop the picture per se, but in stretching it to correct the angled distortion, a portion of the architecture at the sides of the image was eliminated. I knew I wanted to make the correction in post-processing, so

I composed the cityscape with extra room on the sides so the buildings on the left and right could be cropped out without losing the essence of the picture.

Keystoning with telephoto lenses does occur, but it is much less severe compared to using a wide angle lens. In many cases it is barely noticeable.

d. Distorting the image to correct keystoning usually entails an asymmetrical use of the distort tool. As you can see in the screen capture on the previous page, I had to pull the right side handle more than the left side. This is very typical of what you will encounter. §

The Bean in downtown Chicago photographed at dawn to avoid the usual crowds of people.v

URBAN HEIGHTS

Seeking Elevated Perspectives in Cities

Usually a photographer’s initial preconceived images of a city’s architecture or street scenes involves shooting from ground level. Obviously, many great shots can be taken from the ground. Don’t forget to consider, though, there are many other possible locations that afford you spectacular views of a city. Consider shooting from elevated vantages. The views and the images you’ll get are fantastic.

Research is the key to finding great photo loctions. When it comes to finding elevated vantage points to take great pictures, here is what I look for when I’m doing visual research online of a city I’ll be visiting:

1. Rooftop restaurants

2. Rooftop bars

3. Observation decks in skyscrapers that are accessible to the public

4. Hilltop parks

5. Scenic mountain roads above a city