The easy way to fix distortions.

PTLens was recommended to me by a fellow photographer and proves to be one of the easiest ways of fixing four common problems:

• ‘De-fishing’ fisheye images
• Correcting common lens distortions
• Perspective correction (leaning verticals, etc.)
• Correcting chromatic aberration (color fringing) and vignetting – not tested here

It comes in Mac and Windows versions; on the Mac it runs in native 64-bit mode if invoked from Lightroom and is a Universal application, meaning no need for the buggy Rosetta application (which causes spontaneous reboots in Snow Leopard) and supports full 16-bit color TIFF and PSD file formats. It’s a free download permitting 10 uses, whereafter the price is $25 – a very sensible policy.

Up to now I have been using ImageAlign for de-fishing snaps on the 5D taken with the Canon fisheye and Photoshop CS2 (a Rosetta application) and for correcting leaning verticals and barrel and pincushion distortion from Canon’s poor wide-angle lenses. ImageAlign does not work in PS CS3 or CS4. Perspective correction has been done in Photoshop CS2. As for chromatic aberration and vignetting, Lightroom version 2.0 and later does all I need, so I do not touch on that aspect of PTLens here.

I downloaded the PTLens application and installed the the programs (PTLens and PTLensEdit), making the latter the choice in Lightroom under Preferences->External Editing.

Many common lenses are programmed in though not, for some reason, fisheyes. No matter – correcting distortion in the latter is child’s play using the slider.

Here’s an original fisheye image of one of the bedrooms in Hearst Castle where I very much wanted to retain the ceiling in the final image:

Here is the same image ‘defished’ in both ImageAlign (left) and PTLens:

There is no practical difference, defishing rendering the field of view of a 12mm hyper-wide rectilinear lens. PTLens saves the processed file back into the image stack in Lightroom and is very fast, the preview reacting in real time as the sliders are worked. As ImageAlign has folded and the application/PS plugin are no longer available, PTLens is a viable and inexpensive modern alternative.

When it comes to correcting more regular lens distortions, PTLens is in its element, as it has a large database of lenses with all the settings stored for you, whereas Photoshop has none – you have to do everything manually. Here’s an example from the over-rated 24-105mm Canon L zoom which noticeable barrel distortion at 24mm as is clear in this picture:

Barrel time – 24-105mm Canon lens at 24mm.

Here are the before and after images, the latter processed in PTLens using the programmed settings from PTLens with no other adjustments:

Take a good look at the handicapped parking sign before and after correction.

Finally, perspective correction – here’s the picture I published the other day showing the correction of perspective using GIMP; in PTLens it’s even easier.

Before PTLens

After PTLens

A slam dunk purchase at $25 and you can even make it use all four cores of your CPU if it has that many. Highly recommended. PTLens has finally consigned Photoshop to the trash, where I have long wanted to place it. Lightroom and PTLens does all this working photographer needs and neither needs Apple’s compromised Rosetta PPC CPU emulator whose repair is doubtless a low priority in Cupertino, though they do admit its existence: