|TOP: 11mm, 126 Degrees, Rectilinear Lens; ABOVE: 15mm, 180 Degrees, Fisheye Lens. I prefer a rectilinear lens, one that's corrected for both the verticals and horizontals in the frame.|
We get a lot of questions about lenses. You want to know how to get the most from those expensive tools and how to choose new ones for maximum performance and versatility. So let's dedicate this column to talking about lenses in the superlative sense: most, best, sharpest, widest and, of course, longest.
Get The Most From All Your Lenses
Beyond using that tripod I'm always nagging you about, there are a few other basic tasks you need to take care of for best lens performance.
Calibrate the Autofocus. Sharpness depends on the focus being where you expect it to be; but what you see in the viewfinder might not be what's happening at the sensor. When you're following all the rules but still missing the focus, it's time to check the calibration of your camera's autofocus/lens combination. If your DSLR has microfocusing capability, head for michaeltapesdesign.com to check out LensAlign. With your camera/lens mounted on a tripod, photograph the LensAlign targets and calibration charts with autofocus and wide open, then review the resulting capture on the camera's LCD, with a loupe or enlarged on your computer. The chart will tell you if the autofocus is on the money, front-focused or back-focused. Adjust the focus position using the camera's menus, and test again. Once you've found the ideal combination, the camera will remember the adjustment for that lens and correct automatically each time the lens is mounted. I've tested all of my lenses, as well as a number of my colleagues' optics from a variety of manufacturers, and I've been surprised at how many are slightly off; even a minute difference can become critical when using a medium-to-long lens at wide-open apertures.
Use the LCD. The image displayed on the camera's LCD in Live View comes directly from the sensor and shows you exactly what's happening with the focus. For an even bigger view, use a loupe (I use the Hoodman HoodLoupe) and the display magnification feature on your camera. This strategy is especially useful when working on night sky subjects such as the Milky Way and star trails. You want the stars to be pinpoints.
Stop It Down. Sharpness is improved with any lens when it's stopped down a couple of stops. (Caution: If you go too far, you'll lose sharpness due to diffraction.) Use ƒ/22 only if depth of field is more important than a tack-sharp image. For maximum sharpness and depth of field, I often employ focus stacking with a sharp aperture such as ƒ/8.
Adjust the Diopter. This seems basic, but when did you last check your camera's diopter setting? It needs to be customized to your eyesight, whether you're 20/20 or wear corrective lenses, or don't want to wear your glasses when you're photographing. Loan your camera to another photographer for a few minutes, and it's likely to come back to you with a completely different diopter setting, and then you'll be trying to correct focus that has nothing to do with your camera and lens, but everything to do with looking through a viewfinder that's set for someone else's vision. Use the autofocus to attain correct focus on a subject, and then adjust the diopter setting until the data display in the viewfinder and the image are perfectly sharp.
Let's get on to the good stuff. Need to reach out? Start with a good telephoto and take it to the next level with tele-extenders; 1.4X, 1.7X and 2X tele-extenders are available from most of the lens manufacturers. I'd advise staying with a matching converter from the company that made the lens. Yes, some image quality is lost with each converter, but with today's quality optics, you can do some amazing things with a teleconverter—or even two teleconverters—and still have very good sharpness. The 2X will lose a little more sharpness than the 1.4X.
Here are the secrets to maintaining image quality at the extreme focal lengths. Start with a good lens and matched converter, use a sturdy tripod, lock up the mirror or, better yet, work from the LCD using Live View and a loupe. If your camera has Silent Live View Mode (as in Canon), use Mode 1. Precise focus is critical because the depth of field will be minimal with telephotos, and if you miss the focus by an inch or two, the resulting image isn't going to look sharp. Fire the camera using an electronic cable or a wireless unit so you don't touch the camera at the moment of release. The very best system I know is the CamRanger, which operates the camera wirelessly via an iPad or other tablet. You can set your focus using a magnified image, change camera settings, and fire the camera without touching it. I've successfully used a Canon EF 800mm lens with two Canon 2X tele-extenders (3200mm) on a bald eagle nest and obtained publishable images by using the CamRanger. I also use a 500mm lens with 2X and 1.4X tele-extenders to achieve the same excellent results. For more on extreme lens photography, see our article in the April 2014 issue of Outdoor Photographer.
Any lens that offers 20mm or wider on a full-frame camera is an extreme wide-angle, in my opinion. On a smaller APS-C sensor, extreme is at about 12mm. The widest lenses are fisheye types that offer a 180º angle of view. Some record a circular pattern in the center of the frame and others cover the full frame. Obviously, while a fisheye lens gives a fantastic angle of view, it comes with considerable distortion. Unless the horizon is precisely placed through the middle of the frame, it will bend upward if you point the camera down and be bowl-shaped if you point the camera upward. Photography from within a room will produce walls that are distorted outward. It's fun, but it's not real. I prefer a rectilinear lens, one that's corrected for both the verticals and horizontals in the frame. The most common extreme wide-angle rectilinear lens would be the 14mm, with an angle of view of 114º. A new rectilinear lens that I've just started to use is an 11-24mm zoom. At 11mm, the angle of view is 126º, with breadth and clarity that amaze me.
The most common extreme wide-angle is a 16mm, usually part of a wide-angle 16-35mm zoom. The APS-C-sensor-equivalent lens would be a 10-22mm lens. The 16mm angle of view is 108º, which doesn't seem that much less than 126º until you experience it comparatively, looking through both lenses.
In addition to the distortion you'll see in extreme wide-angle lenses, you should be aware of two other shortcomings: light fall-off and chromatic aberrations at the edges. These now can be corrected within the camera and/or with imaging software. Light fall-off is most noticeable when a wide-angle lens is used wide-open. Stop the lens down and it becomes less apparent, and around ƒ/8 should be nearly gone. The software of some cameras actually corrects for light fall-off, but if it's noticeable in the computer, imaging software such as Adobe Photoshop and Lightroom and DxO can quickly balance the lighting. Chromatic aberrations are seen as colored fringing (usually magenta/red and green/cyan) in the extreme edges of the image. Photoshop can minimize this phenomenon, to a degree, but I've found that, with Canon lenses, the DPP software that comes with every Canon camera does a magnificent job of eliminating it. Each lens has a profile, and the software automatically optimizes the capture. Any chromatic aberration I found in the EF 11-24mm lens was magically eliminated!
The greater the magnification, the harder it is to get enough light and a sharp image. Most camera and lens manufacturers offer a 100mm or similar lens and a telephoto macro, such as a 180mm or 200mm macro. These lenses offer a life-size, 1X, or 1:1 capability without any accessories. If you want to go larger than 1X, you'll need extension tubes or tele-extenders. Each time you extend the lens by the equivalent of its focal length, you'll gain 1X. For example, 200 millimeters of extension will bring a 100mm macro lens to 3X. This is a bit unwieldy. Another option is to add a 2X tele-extender to any macro lens to double its magnification. Canon's MP-E 65mm ƒ/2.8 1-5X lens will take you to 5X on a full-frame camera and 8X on Canon's APS-C cameras. You can even add a 2X tele-extender and get excellent 10X and 16X results. You'll need a flash system coupled with this or any macro lens when you go past the 1X magnification.
But, remember, no matter how extreme (and expensive) the optic, it won't do the job unless you use good photographic techniques! See above.
Learn about George Lepp's upcoming workshops and seminar opportunities on his website at GeorgeLepp.com. To watch a video of George's recent daylong class on CreativeLive, "Innovative Techniques for Outdoor Photography," visit CreativeLive.com.