Get perfect perspectives
Beat leaning-in edges and distortion with simple edits
There are a number of ways in which Photoshop can be used to correct lens geometry and perspective, some of which I have described in a previous article ( Keep things in perspective, AP 14 July 2018). But there are also some useful tools in Camera Raw and Lightroom, where it makes sense to apply these adjustments first, at the raw-processing stage. Even photographs captured using the best lenses can benefit from a Camera Raw Lens Profile correction. This consists of two components: a Distortion correction to correct for the barrel or pincushion geometric distortion, along with a Vignetting correction. The Correction Amount sliders allow you to fine-tune a Lens Profile correction. So, for example, if you believe a Lens Profile geometric correction to be too strong or not strong enough, you can easily apply compensation to the correction amount by dragging either of these sliders to the left or right.
You can also apply Upright perspective corrections at the Camera Raw editing stage. These can be either auto-calculated
or, for ultimate precision, applied manually using the Guided Upright option. To apply an Upright adjustment, click on the Transform option in the Camera Raw toolbar. This opens the Transform panel on the right, containing the Upright buttons and Manual slider controls. When you click on one of the Upright buttons, Camera Raw first analyses the image for straight-line edges and, from this, is able to estimate a perspective transform adjustment (to get the best Upright correction results, it is recommended you apply a lens profile correction first). There are several Upright options for you to choose from because no single type of adjustment will work perfectly for every image, so it is
‘Behind the scenes, there are angle of view and centre of projection adjustments taking place’
always worth clicking on each button to see which adjustment works best for an individual photo. It is important to understand that the underlying math behind Upright adjustments is doing more than auto-applying vertical and horizontal adjustments. Upright adjustments are more advanced than that, and the vertical and horizontal adjustments involved in the Upright process are actually quite sophisticated. Behind the scenes, there are angle of view and centre of projection adjustments taking place. This all has to do with the fact that the interaction of one rotation movement can have an effect on another, and such interactions can be quite complex. For example, think about what happens when you adjust the tilt and yaw on a camera tripod head, and you may get some idea of the calculations that have to take place here.
Some of the manual Transform sliders are partly included for legacy compatibility, but they also provide a useful way to tame the outcome from an Upright adjustment. In one of the examples I’ve included here, I describe how it can sometimes help to dial back in a little Vertical convergence to make an architectural subject look more natural. When applying extreme perspective corrections and particularly with Photomerge panoramas, it can often be necessary to adjust the Transform sliders to improve the perspective appearance. For example, using the Aspect slider, you can control how much the image is stretched vertically and horizontally so that the image view looks more natural. Another advantage of applying lens and perspective corrections via Camera Raw is that you can quickly apply these to batches of images. For example, it makes sense to apply lens profile corrections to all your images, which you can save as a default setting for every time Camera Raw encounters a new file. To do this, apply a Lens Correction only to a sample image. Then, go to the Camera Raw right-hand panel fly-out menu and select ‘Save New Camera Raw Defaults’. If you have a series of photographs taken of architectural subjects, you can sync the Transform settings across all the images you have selected in Camera Raw. What this does is syncs the Upright method and/or Manual Transform slider adjustments across all selected photos. The Lightroom synchronise settings have an option that lets you also sync the precise Upright transformation, rather than the Upright mode only.