1

It happened that I shot a some photos in the "Macro/Micro field" by using both:

  • Stacked lens technique
  • Reverse-lens technique

Assuming I wanted to correct lens distortion and chromatic aberration during the postproduction with a software (say, Photoshop)...

  • Is it doable anyway?
  • Should I set the correction sliders opposite to the settings I'd have for the "normal" lens, when I want to correct the reversed one?
  • Is there any library (e.g. those provided by Adobe) available on the internet?
  • Are the lens properly corrected at the end?
1

In short, no to all questions.

Aside from manufacturer-provided utilities (in-camera or otherwise), there is no magic formula for correcting lens abberations in post, nor is there a straightforward way to do this in Photoshop aside from the Lens Correction filter, which has its limitations. Any non-standard lens mounting such as reversing mean that any 'auto' correction tools won't work, so you're left with anything you can pull off in Photoshop.

Why?
The abberations involved are not limited to just barrel/pincushion distortion which are basically all that Photoshop (and other apps') built in 'lens correction' filters can correct.

The notion that mounting identical lenses face to face with a reversing ring unfortunately doesn't mean that they correct each other's abberations, as nice as this would be if it were true. This is due to (practically) irreversible physical effects like diffraction and refraction.

Reversing a lens doesn't also reverse the distortion characteristics, it just changes it in unpredictable ways. Camera lenses are not designed to be reversed, so results will vary widely from lens to lens. However, you can generally expect wide lenses to exhibit more field curvature and spherachromatism than normal lenses when reversed (this is not the same thing as barrel/pincushion distortion though), but beyond that there's no golden rule regarding lens performance when reversed.

  • From the answer below I basically read "distortions of a reversed lens are reversed distortion of a correctly mounted lens"... Are you really sure that if I invert the settings of a lens correction filter I will not achieve what I need? – Noldor130884 Mar 10 '16 at 7:17
  • 1
    Firstly, the abberations involved are not limited to barrel/pincushion distortion which are basically all that PS' filters can correct. Second, the notion that mounting identical lenses face to face with a reversing ring doesn't mean that they correct each other's abberations - nice idea tho. Lastly, reversing a lens doesn't reverse the distortion, it just changes it unpredictably. Camera lenses are not designed to be reversed, so results will vary. However, you can generally expect wide lenses to have more field curvature when reversed (not the same thing as barrel/pincushion distortion). – HamishKL Mar 10 '16 at 20:56
  • Ok that clarifies it. If you would like to add that to the answer I'd gladly mark it as "answered" – Noldor130884 Mar 11 '16 at 6:54
  • Done. Answer updated. – HamishKL Mar 13 '16 at 23:35
0

If you stacked two identical lenses back to back with the same focus (and zoom if applicable) the aberrations would cancel anyway (or rather most would). Two different lenses back to back would require inverse correction for the backward lens and normal correction for the forward lens. Thus two similar lenses would to some extent be self correcting.

You would almost certainly need to correct from first principles for reversed lenses or stacked non-identical lenses. This might mean photographing a grid and adjusting the distortion parameters to square it up, then applying those settings to your real photos. But note that in the macro regime the aberrations change very fast with focus so you'd need to fix the focus between your calibration shot and your real shots, and focus by moving the camera or subject.

  • Do you have any sources for your first paragraph? Would be great to have some proof of this... I thought about that too, but I never seemed to find any confirmation to that... – Noldor130884 Mar 10 '16 at 7:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.