Software aberration correction

A view of the future.

The traditional approach to optical design has always been to try and correct aberrations in the glass. As apertures get larger and focal lengths get shorter, this gets ever harder to do, so you end up with ridiculously oversized lenses, their bulk further compounded by the need to clear flapping mirrors through the use of ever more complex retrofocus designs.

Some of the results of these design dictates can be seen in gargantuan lenses for full frame DSLRs, best illustrated by showing their weight and bulk. Some examples (weight in ozs, dimensions in inches – length x diameter, volume in cubic inches):

  • Canon 14mm f/2.8 L II: 20 ozs, 3.7″ x 3.2″, 29.7 cu. in.
  • Canon 24mm f/1.4 L: 20 ozs, 3.4″ x 3.7″, 36.5 cu. in.
  • Canon 35mm f/1.4 L: 20 ozs. 3.4″ x 3.1″, 25.7 cu. in.
  • Nikon 14mm f/2.8 ED: 24 ozs, 3.8″ x 3.4″, 34.5 cu. in.

Things get worse when you get into wide zooms:

  • Canon 16-35mm f/2.8 L: 22 ozs, 4.4″ x 3.5″, 42.3 cu. in.
  • Canon 17-40mm f/4 L: 18 ozs, 3.8″ x 3.3″, 32.5 cu. in.
  • Nikon 14-24mm f/2.8 EF-S:35 ozs, 5.2″ x 3.9″, 62.1 cu. in.
  • Nikon 17-35mm f/2,8 EF-S: 27 ozs, 4.2″ x 3.3″, 35.9 cu. in.

Without doubt these are some of the finest optics made but take two or three of these in your shoulder bag and you won’t be snapping away for too long before exhaustion sets in.

The other design alternative, of course, dictates smaller sensors which bring with them shorter focal lengths and less bulk. But take that thinking all the way and you get what Panasonic has done with its lens range for its micro-four thirds range of cameras – the G1/GH1 and GF1.

That approach, simply stated, is one of “Get the optics to be as sharp as possible and hang the aberration corrections. Fix all uncorrected defects using software”.

I was thinking how best to illustrate this (the preview of the imported file in Lightroom already has the aberration corrections applied) when it struck me that PTLens has the ability of showing corrected as well as uncorrected images – by comparing JPGs (automatically corrected in Lightroom or Silkypics) with RAW (uncorrected) originals generated in the camera; seconds later I had exported an image taken with the G1 and the 14-45mm kit lens at 17mm (34mm equivalent on full frame) and show the results below. Mouse over the image to see the uncorrected original (Note: The mouse over effect works fine on my Mac with Safari and Google Chrome but not with Firefox or Camino, so please use one of the first two browsers if you have difficulty seeing the images below on a Mac. If you use Windows, please let me know what works so I can post that information here).

The effect of software correction in the Panasonic kit lens at 17mm – mouse over for the uncorrected RAW file.

You can see the remarkable amount of software correction applied quite clearly with software removing severe pincushion distortion. Now these lenses are not as fast as the monsters profiled above, but look at the trade offs in terms of size:

  • Panasonic 7-14mm f/4: 11 ozs, 3″ x 3″, 21.2 cu. in.
  • Panasonic 20mm f/1.7: 3.5 ozs, 1″ x 2.5″, 4.9 cu. in.
  • Panasonic 14-45mm f/3.5-f/5.6: 7 ozs, 3.4″ x 2.4″, 15.4 cu. in.
  • Panasonic 45-200mm, f/4-5.6: 13 ozs, 4″ x 3″, 28.3 cu. in.

These are enormous differences – even greater when the lower weight of the body is added in – and means that you can carry a G1 and a three zoom lens outfit all day without tiring. Weight of the three zooms with the G1 body? 38.5 ounces. By comparison, a Canon 5D body without lens weighs 31.5 ounces. And your 35mm full frame-equivalent focal length range for the G1 kit is an astounding 14-400mm!

My point here is twofold. First, the future of lens design lies with software, not glass. Second, the only good camera is the one you have with you and I can assure you it’s a whole lot easier to take the G1 and a couple of lenses on a hike than it is to take a full frame DSLR similarly equipped.

For comparison, here’s a snap using the overrated Canon 24-105mm L lens on a 5D body – I say ‘overrated’ because it is a nightmare for architectural photography. The approach adopted by Canon/Adobe Lightroom is to leave the extreme barrel distortion at 24mm uncorrected, necessitating a round trip through PTLens or the like to straighten things up. The imported image in Lightroom shows extreme curvature of lines parallel to the edges at 24mm..

The effect of software correction in the Canon 24-105mm L lens at 24mm – mouse over for the uncorrected RAW file.

Panasonic’s approach is, I believe, the future of lens design and I expect all leading manufacturers to embrace this methodology during the coming decade.