Optics In A Digital World

Lenses are limited by the laws of physics, but software can help remove some of those limitations

Optics In A  Digital World While the prices of digital cameras continue to drop, lens costs aren’t keeping pace. The reasons for this are pretty simple. Lenses don’t follow the computer-based Moore’s law that states changes will occur exponentially. They must follow the laws of physics.

And yet, there are things happening with lenses today that offer us new possibilities with how optics affect our images. These are, to me, quite interesting as they offer both quality and creative enhancements to our gear, increasing the possibilities of our equipment.

One thing that higher-megapixel cameras have done is stressed the capabilities of lenses originally designed for 35mm. Many photographers are discovering quality limitations with lenses that worked great with film but exhibit their defects with sensors of 10 megapixels or higher. Manufacturers then have to come out with redesigned lenses that better meet the requirements of digital. This is a clear indication that many digital cameras have passed the capabilities of 35mm film.

Software does come to the rescue. In fact, DxO Optics software can increase the image quality of a photo taken with certain lenses and sensors. DxO is quite a remarkable program. The engineers at DxO actually measure the performance of lenses with specific sensors, then create corrections based on that unique combination to give you a file with the highest-quality image.

Image sharpness, brilliance, aberration correction, vignetting and more are analyzed and adjusted automatically by the program. The technology behind this is pretty heady—I only understand some of it. But I certainly understand the excellent results. This can mean you get more from an older lens or that you improve results from a less expensive lens.

Adobe has also put some basic lens-correction capabilities into its software. Photoshop CS3 (and CS2), Camera Raw and Lightroom all allow you to correct some color aberrations as well as vignetting caused by the lens. This isn’t as refined or sophisticated as DxO Optics, but it does work. In Photoshop, these are under Filter > Distort > Lens Correction. In Camera Raw, look for them in the Detail tab. And in Photoshop Lightroom, you’ll find them in the Develop Module in Lens Corrections.

Optics In A Digital WorldLens aberration effects show up along contrasty edge detail in the photo near the actual edge of the frame. The best solution is to enlarge the photo so you can better see the defect. You’ll see edges that include extra colors, often green or red. These colors only exist because the lens is having trouble controlling the focus points of different colors of light.

Try the correction sliders in Photoshop’s Lens Correction until something works for you. The program shifts pixels among the different color channels but only along the outer part of the photo. The technology is quite remarkable, and you should see a dramatic adjustment.

Lens distortions also can be corrected in Photoshop CS3 with the Lens Correction filter (though not in Camera Raw or Lightroom). Technically, a lens distortion that’s caused by limitations of optics is an aberration, but usually that term is reserved for defects such as chromatic aberration (where colors focus at different points), especially since you can purchase a full-frame fish-eye lens that has deliberate distortion yet is highly corrected for aberrations.

One unintended distortion that’s pretty common today is barrel distortion where straight lines away from the center of the photo bow outward (less common is pincushion distortion where the lines bow inward). A lot of zoom lenses, especially the low-priced models or extreme focal-length optics, will show barrel distortion along the edges. This comes from the big challenge of moving light through a complicated zoom lens design. But it’s not a problem with a lot of nature photography because there are few perfectly straight lines in nature.

Horizons and straight trees can be exceptions, though, and often look better with some correction. They’re easily corrected with the Remove Distortion slider in Photoshop’s Lens Correction filter. If you don't have the right version of Photoshop or you have another program, you also can find this correction in DxO software, in the 55mm plug-in from Digital Film Tools or in the LensDoc plug-in from Andromeda Software. You can find any of these by Googling them on the Internet.

Now full-frame fish-eyes take this sort of distortion to a different level. They give an intentional curvilinear distortion that exaggerates the natural perspective of a really wide view of the world. They become a creative part of the image itself. If you don’t have such a lens, you can try the look with the Lens Correction filter, too, by increasing the distortion instead of removing it.

Full-frame fish-eye lenses can be addictive. Their unique curvilinear perspective and very wide field of view demand your attention. Trees curve dramatically, the horizon looks like the edge of a globe, foreground-to-background relationships change radically, and frankly, I find these lenses a lot of fun to use.

But that extreme curvilinear perspective can get a little tiresome, too. After all, there’s a limit to how many curved trees, curved cliffs, curved horizons and so forth, you want in your photographs. I’ve always felt it would be nice to have the capabilities of a curved perspective and the standard rectilinear perspective of most wide-angle lenses in one lens (rather than the fish-eye’s extra wide angle of view), but lenses don’t work that way.

Again, software comes to the rescue so you don’t have to carry two lenses. You can remove a fish-eye’s perspective in the Lens Correction filter, but it has to work hard to change that perspective distortion—work that’s a little beyond its quality capabilities.

DxO Optics, though, has an automated control that will pull out the curvilinear distortion and give a very wide-angle view with rectilinear perspective. It holds image quality quite well—you’d think the image was shot with a rectilinear wide-angle from the start.

Image Trends has introduced the Fisheye-Hemi plug-in to correct the full-frame fish-eye lens curves in a different way. Basically, most standard software corrections use what are called rectilinear mapping techniques. These techniques tend to distort shapes at the sides and corners, plus they often lose resolution and some of the image area as shot. The engineers at Image Trends developed unique algorithms that map the correction with a much more natural look. Fisheye-Hemi takes out the distortion without adding new distortion to recognizable shapes.

What that means to the outdoor photographer is that most shapes will have a more natural form when the correction is done. The photo just looks right. Plus, the Image Trends folks have done a great job of retaining resolution from the original shot as well as keeping most of the photographer’s original framing. The ultimate sharpness of the image will depend on the camera and lens used.

I love the possibilities with this. Even if there are no curving horizons in the photo, use of this one-click software removes the visual "bulge" look that a full-frame fish-eye has.

I have shot close-ups with the Olympus Zuiko 8mm full-frame fish-eye—sometimes I love them, sometimes they just don’t quite look right. With Fisheye-Hemi, I essentially have two lenses in one. I can use the images straight or adjusted.

Digital photography has definitely given us many new opportunities for creating interesting and creative images. Combining lens optics with software corrections and enhancements, we can take photos further than ever before.


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