I received a nice email that I answered this morning. Gray wrote to compliment my photos, mention an interest in my workshops and to ask about what lens I use for my wildlife images. It seems he’s been using a “super zoom” lens for about a year and is having a challenge getting sharp images with it. I know that this is something a lot of folks struggle with so I thought I’d do an article on the subject.
When I use the term “super zoom” I’m referring to a zoom lens with a long telephoto reach… say at least 300mm… and a wide zoom range… maybe 200mm or more. There are many popular and affordable lenses in this class offered by after-market manufaturers like Sigma, Tamron and Tokina. Additionally most camera manufacturers offer OEM lenses in this class. They are attractive to budget minded folks and for those who need some versatility in the equipment they carry afield. While this article is directed at zoom lens use, most of the techniques discussed also apply to shooting with fixed focal length telephoto lenses as well.
Let me start by saying you can never expect a zoom lens to match the resolution, sharpness and contrast you’ll get from a prime (single focal length) lens. That’s a matter of mechanics and physics that’s going to prevent that level of performance. For the convenience of versatility you pay a bit of a price. That’s not to say you can’t make quality images with these lenses. You most definately can. There have been many images published and that have won awards that were made with this class of lens. It’s a matter of knowing your equipment, using good technique and a quality post processing workflow.
As a general rule these lenses do not produce their sharpest images when used at their wides aperature settings. (Remember, smaller number equals wider or open aperature… larger number equates to a smaller or stopped-down setting). Individual lenses will vary a bit but usually you need to set your aperature at around f/7.1 or f/8.0 to enjoy the sharpest results. Image quality may start to drop-off at aperatures above f/16 due to refraction. Work within that range and you should be seeing the sharpest results you can expect from your zoom lens.
Shutter speed is an important aspect in long lens use. The standard advice is to shoot at a shutter speed equal to or faster than the focal length of the lens. For example if you’re shooting a 300mm lens your slowest shutter speed used should be 1/300 of a second. This is a rule of thumb and like most rules in photography, not set in stone. If you’re using a sturdy tripod and applying good “long lens technique” you can get away with a bit slower shutter speed. When hand-holding a long lens you may need to use an even shorter shutter speed.
One of the issues involved in making sharp photos when using a long lens is that there are vibrations that travel up and down the length of the lens barrel that creates blur in the final image. The vibration can come from mirror slap while taking the photo, from wind blowing against the lens and even from how one trips the shutter release. There are several techniques that can be used to counter these vibrations. Hand shake or subject movement can also casue blur. Any movement is severely magnified by long lenses resulting in blurred photos.
Using a tripod whenever possible will go a long way towards making sharp photos with a super-zoom lens. It’s important to use a tripod that is designed to be sturdy enough for the weight involved and to use a quality tripod head as well. There are a number of well-built ball heads and gimbal mounts on the market that are suitable for use with a long lens. Simiarly there is a wide variety of suitable tripods available. There’s more to using a tripod than just putting your camera on top of it and shooting. It’s important to use proper long lens technique as well.
When making photos with a long lens on a tripod push your face up against the back of the camera. An eye-cup can be a nice addition for this technique. The idea here is that you’re using your face as a vibration dampening device. Also rest your hand on top of the lens, about at the point where it attaches to the tripod head or slight further out. Again your using your hand to dampen vibrations. Rest it atop the lens much as if you were laying your hand in your lap. A lot of photographers will position themself in a manner that allows their elbow or arm to make contact with the tripod or mount. Again, the goal is to dampen vibrations. There are also several proponents that suggest that one of your legs makes contact with the tripod leg. When you trigger the shutter don’t just poke at the button but roll your finger over it. The idea is limit motion and vibration to insure the sharpest image possible.
One last consideration. Zoom lenses are seldom at their sharpest when used at the maximum focal length. A zoom lens with a maximum focal length of 500mm will usually be a bit sharper around 400mm to 450mm. While reach is important there can be advantages to pulling back a bit from the longest reach. As with all man-made items individual lenses will behave a bit differently. You need to get out, shoot and experiement to find how your version behaves.
While there is some compromise involved in using super-zoom lens for bird and wildlife photography with proper technique and a little knowledge they can produce high-quality images. Spend some time in the field experimenting and taking notes on settings, learning what does and doesn’t work with your lens. Whenever practical use a tripod and always use good long-lens technique to see a real improvement in your telephoto images. For an excellent source for quality tripods and tripod hears check out Outdoor Photo Gear. Obviously the tricks, techniques and technical considerations needed to make sharp, compelling photographs in the field are topics covered in my various photography workshops. While an article will go a long way to getting you started on the right track, nothing beats receiving input from an observant instructor.