Thursday, February 5, 2009

Designed For Digital Lenses

From fixed-focal-length prime lenses to wide-angle to telephoto zooms, modern lenses use a complex combination of high-end glass, unique materials and chemical cocktails capable of producing optics with incredible power.
By Dave Willis Published in Lenses
Designed For Digital Lenses
AF-S DX Nikkor
ƒ/3.5-5.6G ED VR


So if extra magnification is beneficial in most cases, why not use full-frame lenses on sub-full-frame bodies? For one thing, there’s the extra cost of producing full-frame lenses, which are more expensive not only because of specialized production, but also because of a lower market demand. More importantly, magnification is actually a crop factor, which reduces image quality when compared to a lens that has been designed to match a particular sensor.

With smaller sensors, the image circle (the image projected to the sensor plane) also is smaller so optics can be designed to be more compact. Less material is used to manufacture the lenses, so they’re less expensive to make. Lenses designed specifically to match the precise dimensions of a smaller sensor also provide higher resolution by matching the dimensions of a sub-full-frame image field.

Conversely, lenses designed for sub-full-frame sensors can’t be used with full-frame sensors because the image circle is too small, which would cause extreme vignetting—so extreme, in fact, that the image won’t fit the whole sensor, which produces a perspective similar to the circle of a telescope.


With analog lenses, flaws in design would have required an entirely new lens to be produced. Cameras have become computers themselves, though, and lenses now feature digital technology that has been incorporated into the body. Digital communication between the lens and the camera provides autofocusing that’s precise and fast, and often lenses can be updated through firmware fixes that optimize performance even after the lens is in the hands of photographers.

Canon EF-S 18-200mm
ƒ/3.5-5.6 IS

Digitally designed lenses also utilize special coatings for reducing optical aberration, ghosting and flare. This is especially important with the highly reflective surfaces of D-SLR sensors. These coatings are able to shape the light as much as the glass does, and thanks to their introduction, lenses are now much lighter and more precise. All of this should give you an idea of just how complex lens design is. However, while lens construction has certainly become more advanced, the same goal remains: a sharp image without sacrificing speedy shooting.


Canon’s EF-S line of lenses are designed to meet the exact specifications of its APS-C sensors, present in the majority of its D-SLR cameras on the market. The efficient image circle is smaller and, therefore, the lenses are lighter, more compact and more affordable. The EF-S 18-200mm ƒ/3.5-5.6 IS, for instance, has a wide magnification range from wide-angle to telephoto with a 35mm equivalent of 29-300mm. The lens features an Optical Image Stabilizer for up to four stops of compensation, even at full zoom. Estimated Street Price: $599.

Olympus Zuiko Digital
ED 9-18mm ƒ/4-5


Nikon’s sub-full-frame (DX) format is roughly two-thirds the size of its full-frame FX sensor, providing an approximate 1.5x magnification factor, making the 35mm equivalent of the Nikon AF-S DX Nikkor 18-105mm ƒ/3.5-5.6G ED VR lens a healthy 27-157.5mm range. The lens also includes a built-in Silent Wave Motor for quiet focus and Vibration Reduction for up to three stops of camera-shake compensation, which can be seen through the viewfinder. The lens uses an Extra-low Dispersion (ED) glass element with an aspherical lens element for exact image reproduction. Estimated Street Price: $324.


Olympus offers only sub-full-frame sensors, a move that coined the term “designed for digital,” thanks to its Four Thirds System, and more recently the Micro Four Thirds System, codeveloped with Panasonic. The E-System of Zuiko Four Thirds lenses features compatibility with Four Thirds cameras from Olympus, Panasonic and Leica. Thanks to the smaller sensor sizes, Four Thirds sensors also feature a doubled focal range in a 35mm equivalent lens. The Zuiko Digital ED 9-18mm ƒ/4-5.6 (18-36mm equivalent) uses a Dual Super Aspherical lens to keep this extreme wide-angle compact at 280g and 73mm long. Estimated Street Price: $541.


  • Comment Link Len Straub Tuesday, March 3, 2009 posted by Len Straub

    Although I have a number of both zoom and prime lenses, it's always my preference to use prime when possible. I have both a Nikon 85mm 1:1.8 D and a Nikon AF Micro Nikkor 60mm 1:2.8 in my kit that I have always used for portrature with my D200. Recently I tried to use one of these lenses for a scenic, at infinity, simply because the focal length suited my needs. After a bunch of fooling around I finally realized that neither of these lenses focus to infinity with larger aperatures. I had to switch to manual aperature and stop down. I've always known that all lenses have a minimum focus distance but wasn't aware that many also have a maximum. Would you please comment on this? Users may inadvertently be taking low quality pics without knowing why.

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