Correcting Images Using Photoshop Lens Correction Technique

When the optical train hasn't been fully optimized, one often ends up with star shapes flaring in the four corners of the image while looking nice and round a the center of the image. These flares are typically the result of the focal plane not being exactly perpendicular to the image axis, field flatteners missing or not optimally positioned, spherical aberration, etc.

The Photoshop Lens Correction tool (Filter / Distort / Lens Correction) can help correct some of these optical problems by enabling the user to digitally tilt the image horizontally and vertically, and add a "digital" lens to pincuhion or barrell the image.

The example below shows the four corners of a test image zoomed at 600% before and after applying the lens correction. In this specific case, the lower left and right corners have the most star elongation, while the upper left and right are reasonably good. As shown below, this test image can be corrected to a large degree by applying a -5.00 (barrel) distortion, -9 vertical perspective, and +5 horizontal perspective to correct the star shapes.

Once the Photoshop lens correction is applied, one can then simply crop the image in a rectangular form to complete the operation.

(Acknowledgement: Test image used in this example was provided by Kerry-Ann Lecky Hepburn)

 

Test Image Lower-Left: Before and After

 

Test Image Lower-Right: Before and After

 

Test Image Upper-Left: Before and After

 

Test Image Upper-Right: Before and After

 

 

 

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© All images on this site are copyright Serge Théberge, 2009