Lens Correction

• Barrel and Pincushion Distortion
• Chromatic Aberration
• Vignette
• Horizontal and Vertical Perspective
• Angle and Straightening Horizons

Barrel Distortion

Original	After Photoshop CS2	After PTLens
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Original The distance between the red reference line and the glass of the building is large in the top and bottom crops.	Photoshop CS2 (setting +5) The distance between the red reference line and the glass of the building is reduced in all crops but the reduction is not constant.	PTLens The red reference line is perfectly parallel to the glass of the building from top to bottom.

The above results show the limitation of having only one parameter available in Photoshop CS2. Increasing the correction parameter to more than +5 would further improve the correction in the first and third crops, but would introduce pincushion distortion in the corner areas (there is already a hint of pincushion distortion in the bottom crop).

I'd say that if you want a quick and easy correction that combines other corrections such as straightening horizons, adjusting perspective, vignetting and chromatic aberrations, the Photoshop CS2 Lens Correction filter will lead to visually acceptable results in most cases. However, if you are a perfectionist or are working on a mission critical image, the free PTLens plug-in will provide a higher level of accuracy.

Chromatic Aberration

The chromatic aberration correction provides a reduction that varies more with the image than is the case with Adobe Camera Raw (discussed on the next page), which in many instances eliminates all chromatic aberration. In the first example, the chromatic aberration correction performed nearly as good as in Adobe Camera Raw (if you look at the enlargement, there are some color artifacts around the edges in the lens correction crop). In the second example, the chromatic aberration correction performed less well than Adobe Camera Raw as quite a bit of chromatic aberration remains.

Original with Chromatic Aberration	After Photoshop CS2 Lens Correction on JPEG	After Photoshop CS2 Camera Raw 3.1 on RAW
Original with Chromatic Aberration	Chromatic Aberration virtually eliminated	Chromatic Aberration completely eliminated
Original with Chromatic Aberration	Chromatic Aberration only partially eliminated	Chromatic Aberration completely eliminated

Vignette

Unlike chromatic aberration correction, the vignette correction performed equally well as in Camera Raw. And unlike the barrel and pincushion distortion, it performed better than PTLens as well. Note that in order to achieve visibly similar results, the vignetting slider adjustments in the Camera Raw window will be different than those in the Lens Correction dialog box.

Original
1,007 KB
Notice the vignetting in the right corner

After Photoshop CS2 Lens Correction	After PTLens
1,007 KB	1,096 KB
Vignetting is completely removed	Some vignetting remains (more visible on full size image)

Transform

The perspective and the angle adjustments are the same as those in the Image -> Transform command. There is also an angle tool to automatically straighten horizons (similar to what you can achieve with the Measure tool). So although this is nothing new, it is very useful to have those adjustments available in one dialog box while doing other lens corrections.