If you care about getting your digital photos correct—that is, looking as close to the scene you saw before you—lens-profile-based image correction is your ally. The foremost exponent of this technology has, unsurprisingly, been Adobe, with its Photoshop CS6 and Lightroom 4 apps offering leading lens-profile-based image corrections. Camera calibration software maker DxO is a leader in this field, too, with its DxO Optics Pro 7. This kind of correction is particularly important when it comes to geometry issues introduced by lens optics, such as pincushion (from wide-angle lenses) or barrel distortion (from telephoto lenses).
Lens physics also comes into play with chromatic aberration—those color fringes at high contrast edges, and with vignetting—the effect of darkening at the edges of the photo. PTLens’s home page claims that it was the first software to automatically correct these kinds of lens distortion. Let’s see whether this $25 single-task program can still keep up with the big boys of photo adjustment.
PTLens is available for both Windows and OS X PCs, though the Windows version is at 8.9, while the Mac version is still at version 1.6. A trial version only lets you work on 10 images. The Windows version works with OS versions all the way back to Windows 2000 or later, while the Mac one works on 10.5.2 and later systems. The installer is a tiny sub 4MB download.
You can also install PTLens as a Photoshop plugin, for Photoshop versions back to CS3. The Windows download is a ZIP you have to extract, and then you run a standard MSI that takes you through an installation wizard. When I run this, it asked me if I wanted to additionally install PTLens as Photoshop and Photoshop Elements plugins, which is a help. On first run, you choose your language from a dropdown, and are informed how many processors are in you system, e.g., 4 for a quad core.
PTLens’s bare-bones interface uses a single window, and its non-standard control layout makes using it less intuitive than more polished apps. The File menu didn’t let me open a photo as I expected it might, instead, to get started, you click the “Directory” button at top right. This opens a typical system-folder tree. Once you choose a folder, the image files are listed below the button, and clicking on one displays the photo in the main large window on the left. Below the image are the camera and lens selection dropdowns and option buttons for geometry correction of barrel-pincushion, Fisheye, or none.
Next to the file list on the left is a tabbed section with correction sliders. Its three tabs are Vignetting, Perspective, and Chromatic Aberration. Zooming was only available in the Chromatic Aberration tab, which makes sense. A final help is the Preview check box, which lets you switch between viewing the corrected and original image; even easier is just holding the mouse button down while the cursor is over the image to show the unmodified version. Convenient Reset buttons on each tab let me undo adjustments gone awry.
When using PTLens as an external editor with Lightroom, it only worked if I chose to edit on the original, not a copy that Lightroom offered at the handoff.
On my first try, the software correctly identified my DSLR, and displayed the focal length and aperture, but I had to tell it which lens model I was using—something Lightroom can figure out by itself from the image’s EXIF data. Happily, my 55-250mm lens was the top choice in the option list. Once I selected the lens, the edges of the photo were cropped unevenly to make up for the geometry correction, which is normal. You’ll want to go back and crop in your image software to straighten out the edges after, or you can use PTLens’s Scale slider in the Perspective tab to do this or you can check the “resize to remove black edges from pincushion images” box in Options.
By default, the program uses the same settings from the previous image, since a batch of images you’re working on will often require the same corrections. On my first test, even after I chose the lens I shot with, the program only corrected geometry, not chromatic aberration, or vignetting, as DxO and Lightroom did. But more troubling was that the Red Cyan slider in the chromatic aberration tab did nothing to my image when I slid it.
The problem? I was working on a JPG image without the necessary metadata. When I opened a CR2 raw file, everything but vignetting was corrected automatically. But there was another problem: The chromatic aberration was overcorrected, to the point of producing a worse distortion than the original. By comparison, Lightroom’s built-in chromatic aberration correction did as close to a perfect job of removing the color fringes on the same test image, as does DxO Optics Pro.
On another test with shots from a Sony SLT-A77V with a DT 16-50mm lens set at the widest focal length, I saw good geometry corrections, though vignetting again wasn’t changed, and chromatic aberration again was overcorrected for a worse result than the original.
If you want more than simply “correct” geometry, PTLens’s Perspective tab lets you simulate a tilt-shift lens: For example, it let my change a photo of a building taken on a steep angle to look like it was shot straight on.
The Best Lens Correction?
PTLens deserves hats off for being a pioneer in the lens-profile-based corrections field. Once you’re familiar with its quirks and limitations, it can do a fine job of correcting geometry, and it’s a reasonable value at $25. Just don’t rely on it for chromatic aberration correction. But for more effective corrections, look to DxO Optics Pro, which offers similar but superior functionality, or to our Editors’ Choice photo workflow applications, Adobe Lightroom, which does this stuff and a whole lot more.
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|OS Compatibility||Windows Vista, Windows XP, Mac OS, Windows 7, Windows 8|
Copyright © 2012 Ziff Davis, Inc