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Monday, April 28, 2008

Fast Lenses On Sub-Full-Frame Sensors

Quick, inexpensive and light, sub-full-frame lenses aren't just for the amateur market anymore


This Article Features Photo Zoom

fast lenses

While full-frame D-SLRs offer the highest in professional quality, often what really matters is pure, unadulterated speed. In the realm of full-frame vs. sub-full-frame lenses, fast, compact and superb image quality is the precedence from which lenses are judged. But when pro levels of speed and quality are avail-able at sub-full-frame costs, it might be time to take a look at the offerings.

The majority of D-SLRs on the market have a sensor that's smaller than the film plane of traditional 35mm-film (36x24mm) cameras. Known as sub-full-frame sensors, they are available at price points far below the cost of your Canon EOS-1D Mark III or Hasselblad H3DII. The advantage to a sub-full-frame sensor, from a manufacturer's point of view, is that they save on time and cost for development and construction when tailoring a lens to a smaller image sensor.

fast lenses
fast lenses
CANON
The EF 70-200mm ƒ/4L IS USM is literally less than half the weight of the ƒ/2.8 version and also has a lower cost. It's not drastically lower, but is roughly the difference between $1,850 for the ƒ/2.8L version and $1,150 for the ƒ/4L. And even though it's less than half the weight, its image quality is at least as good as the ƒ/2.8 version. It has at least as good professional construction in terms of moisture and dust resistance. All such benefits that a professional lens should have are there; it's just a smaller, lighter version of it.
—Chuck Westfall

“With EF-S lenses,” notes Chuck Westfall, Canon's Director of Media and Customer Relationship, “the typical image circle when the lens is focused at infinity is approximately 27.3mm in diameter, whereas with the EF lenses, the typical image circle at infinity is approximately 43.3mm in diameter. The smaller image circle of the EF-S lenses enables us to make them smaller, lighter and more affordable than they would be if they had to cover the 24x36mm imaging format of full-frame EOS SLRs.”

On the other hand, one of the difficulties with sub-full-frame sensors is that there are a smattering of individual sizes and formats. Manufacturers spend a lot of time and money developing sensors that work best with their own system. Canon, for instance, has two competing sizes within its own line of cameras, APS-H at 28.7x19mm, and APS-C at 22.2x14.8mm. Olympus developed its Four Thirds System at 17.3x13mm, Nikon's APS-C-sized sensor size is 23.6x15.7mm, Sigma is 20.7x13.8mm, Sony uses a 28.0×22.3mm APS-C and so on.

To top it all off, any confusion caused by varying sensor sizes is minimal when compared to the amount of lenses available. From fixed-focal lengths (primes) to wide-angle to telephoto, the only constant is that each lens has its own individual construction, utilizing unique combinations of glass, material and chemical cocktails.

The dizzying complexity to lens design has been streamlined a lot because of, and thanks to, the digital revolution. So while the construction of a lens is certainly more advanced, the goals have always remained the same—sharp images from a lens with a fast and constant aperture.









Speed Demons
The importance of a fast lens for a traveling photographer looking to cut down on some extra weight can't be overstated. Fast-aperture lenses made specifically for APS-sized camera sensors offer exceptional low-light performance and speed for photographers. Here are some choices from the manufacturers themselves on which lens they carry with them on the road.



 

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