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Real World Camera Raw: the Lens Corrections Panel

Contents

  1. The Profile Subpanel
  2. The Manual Subpanel Transform Controls

Article Description

Jeff Schewe shows you how you can use both the new Profile and the Manual subpanel controls in the Lens Corrections panel to correct for lens defects and do perspective corrections, precise rotation, and scaling.
The Manual Subpanel Transform Controls

The Manual Subpanel Transform Controls

While it might be a bit optimistic to hope that completely automatic lens corrections can be now accomplished, sometimes you have to take the hands-on approach and do things yourself. The Manual subpanel of the Lens Corrections panel enables manual control over lens corrections as well as correcting for distortion, adjusting both vertical and horizontal perspective, fine-tuning rotation, and adjusting the scale of the image. It’s also where the old manual Chromatic Aberration, Defringe, and Lens Vignetting controls live. Figure 4-34 shows the full Manual subpanel.

Figure 4-34 The Manual panel in the Lens Correction dialog box and the image we’ll be using to shoaw the Manual Transform controls.

It’s pretty remarkable that the Camera Raw team has engineered the ability to parametrically correct not only for lens defects but also for perspective problems as well. This is an impressive addition to the Camera Raw toolset. The Manual Transform controls are as follows:

Distortion. The Distortion transform in the Manual subpanel has the same sort of geometric distortion correction you find in the automatic lens corrections. The manual controls correct between barrel and pincushion distortions only, however. The Profile-based corrections can also correct for other lens distortions such as a “mustache” distortion (yes, a distortion shaped like a mustache). Pressing the Up or Down arrow keys changes the units by a single digit.

Vertical. The Vertical correction transform will correct for keystoning, the distortion that occurs when you tilt a camera up to include the top of a building, for example. Pressing the Up or Down arrow keys changes the units by a single digit.

Horizontal. The Horizontal correction transform is essentially the same as the Vertical transform but designed for lateral perspective corrections. Pressing the Up or Down arrow keys changes the units by a single digit.

Rotate. The Rotate command allows numerical rotational correction that is more precise than Camera Raw’s Straighten tool. Pressing the Up or Down arrow keys changes the units in increments of 0.1. The range is plus or minus 10 degrees.

Scale. This command allows scaling the image up or down from 50% through 150%. This is useful when trying to subtract or add to the image after manual transforms without using the crop tool. Pressing the Up or Down arrow keys changes the units by a single digit.

We’ll show you what the controls do on a synthetic image (it’s actually a close-up on a shot of a lens-profiling target). We hope the alternating checkerboard pattern doesn’t make you nauseous! The baseline image and the Manual subpanel of the Lens Corrections panel are shown in Figure 4-34; the effects are shown in Figures 4-35a and 4-35b.

Figure 4-35a The effects of the Manual Transform controls.

Figure 4-35b The effects of the Manual Transform controls.

You’ll note that in the images where the controls result in the actual image data being altered beyond the original boundaries, a gray null image area is added. This can be useful if the image correction results in a nonrectangular result. You can choose to keep the additional gray area or use the Scale control to make the overall image larger. Another alternative to using the Scale control is to use the Camera Raw Crop tool. Figure 4-36 shows drawing out a rectangular crop of the image. A new function of the Camera Raw Crop tool is the option to have the crop either constrained to the image or unconstrained depending on the option in the Crop dropdown menu. If the Crop tool is constrained to the image boundaries, none of the added gray filler will be in the final cropped image (shown in Figure 4-36).

Figure 4-36 Cropping in the Lens Correction panel

The last important function the Camera Raw team provided in the new Lens Correction panel is the ability to overlay a grid to aid in the alignment of both rotation and perspective transforms. You can display the grid by pressing the V key when you are in the Lens Correction panel or by navigating to the Camera Raw flyout menu and selecting the Show Grid command (see Figure 4-37).

Figure 4-37 The alignment grid overlay in the Lens Correction panel.