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Tuesday, June 10, 2014

Gadget Bag: Extreme Telezooms

Get supertele reach and zoom versatility, plus stay cash-flow positive. We look at the pros and cons of lenses with 500mm and more.

Labels: Gadget BagGear
This Article Features Photo Zoom

Dramatic photos can be achieved with extreme focal lengths.

One of the major challenges for wildlife and sports photographers is getting close enough to the subject. We need reach. The big challenge with big reach is cost—500mm and 600mm superteles cost $10,000 and up. The solution is the extreme telephoto zoom. Sigma and Tamron offer zooms that go out to at least 500mm for around $1,000. These zooms may not perform like a $10K prime, but they're capable of delivering sharp images of distant action.

The extreme telezooms also offer a big advantage over the prime supertelephoto lenses: They zoom. It's hard to "find" a flying bird looking through a 500mm or 600mm lens, especially on an APS-C DSLR, with its 1.5x crop factor, which gives a 500mm lens the even narrower angle of view of a 750mm on a full-frame camera. With a zoom, you can start at the wider angle of view of the shortest focal length, then zoom in on the subject when you have it in the finder.

The $1,000 extreme telezooms weigh 4.3 pounds or less. The 500mm ƒ/4 primes weigh 7 pounds and more, and the 600mm ƒ/4 primes weigh 8.6 pounds and up. While 4.3 pounds isn't light, it's a lot easier to carry—and handhold when you need to—than 7 pounds and more. Of course, for optimal sharpness, any lens should be used with a tripod, especially longer ones.

Tamron SP 150-600mm F/5-6.3 Di VC USD
Minimum Focusing Distance
Another advantage of the extreme telezooms is their relatively short minimum focusing distances. The 500mm ƒ/4 lenses have minimum focusing distances of 12 feet and more, while the $1,000 extreme telezooms focus down to 8.9 feet or closer. This doesn't make a lot of difference in terms of maximum magnification (the optical systems used in the zooms don't deliver as much magnification at minimum focusing distance as a prime would if it focused that close), but you'll be able to keep shooting should a subject approach more closely. Most of the low-cost extreme telezooms focus down to 0.20x magnification (1/5 life-size at the image plane), while the supertele primes just go down to 0.14x (1/7 life-size).

Here's where the costly prime super-telephotos have a big advantage—ƒ/4 is 1.3 stops faster than ƒ/6.3, which is the maximum aperture of the low-cost extreme telezooms at their longest focal lengths. That means you can use a faster shutter speed or a lower ISO setting with the prime than with the zoom in a given light level, and have a brighter viewfinder image to work with.

The fast 500mm and 600mm primes usually autofocus more quickly and perform better optically than the $1,000 extreme telezooms. As we've said, that performance comes with a $10,000 price tag. The two main contenders in the $1,000 extreme telezoom category are Sigma and Tamron.


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