Perspective control lenses are as vital to the architectural photographer as their cameras, the ability to control converging verticals in this particular field of photography is a given. For most of us, however, a PC lens is way beyond what we can justify paying for a lens that may not see much action. There is however, a software solution, using plugins for programs like Aperture or Lightroom or using Photoshop’s own built in perspective control abilities, namely the Lens Correction filter. As with all software based techniques, it should be stated that the effect will never quite match that of using the “real deal” however for the most part it is a very useable alternative.
Before we go any further, lets explain why we need perspective control. As you will know, very often, in order to get an entire structure in frame, you will need to tilt your camera upwards. This causes, what we call “converging parallels” or the effect that the two sides of the building you are photographing are coming together like railway tracks in the distance. Whilst this can be used for creative good, often we are trying to get a more natural feel to the image, as our eyes would see it. For this we can use perspective correction.
So lets open an image in Photoshop and get started. The image you wish to correct must have some space around it, top bottom and sides. This is because we are going to use that space to straighten the verticals. We also need an images that does not have too steep a converging vertical.
So with the image open, from the Photoshop menu select Filter – Lens Correction. The image will open in a new window with a number of tools around it.
Get Your Horizon Straight!
The first thing we will do is make sure that the horizon is straight, there is no point in correcting the image if you have a wonky horizon. To do this we will use the straighten image tool, which is the second tool down on the top left of the window. What we do, is find a horizontal part of the image at around eye level and click and drag a line along it. This will bring the horizon straight. To aid us with this, make sure you have a Grid overlay switched on. This can be done from the bottom of the window by checking Show Grid.
Next from the tools on the right, click on the first tab called, Auto Correction. Underneath you can select your camera model and lens model. This will apply corrections for any distortion you lens may have.
Now Move Onto the Verticals
Now click on the second tab, Custom. Ignore the controls at the top, we are looking for the Transform controls at the bottom. The most important of these is the Vertical Perspective control. To use the tool click and drag it left or right. For the most part you will have verticals that are converging upwards, to correct this, slide the slider to the left until the main verticals in your image are upright. You may also have Horizontal Perspective issue, these occur when the camera is not parallel to the subject. Use the horizontal slider to correct this.
You may now have found that important elements of your image have been cropped out. In our case the cross on the first dome. In the image we have spare space at the bottom, so to bring the cross back we will use the Scale tool. Sliding this left will zoom the image out returning our cross but as you can see there are now problems at the bottom. These we will simply crop out.
So lets finish with the Lens Correction tool by clicking OK. This returns us to the main Photoshop window, where we can see, the canvas showing through at the bottom. To remove this, select the crop tool and resize the image as required.
The final result is a perspective corrected architectural shot without the need for an expensive PC lens. As we mentioned at the top, this technique will never replace a true PC lens, but with the right image it can create a very similar effect.