The joys of 4/3

Started Nov 16, 2009 | Discussions thread
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al_in_philly Regular Member • Posts: 478
The joys of 4/3

Just a thought or two to share:

There's a fair amount of moaning and groaning on this forum about Oly and other 4/3 cameras producing higher signal to noise levels at low light levels. But here's another aspect of 4/3 imaging design which you might want to ponder as well: the smaller 4/3 sensor is the primary reason behind Zuiko's superior optics.

Let me explain. As we all know, the 4/3 sensor is smaller in area than an APS-C, APS, or full-frame sensor. That's why for a given number of pixels, a 4/3 camera will have higher noise levels (more photon number variation between sensor elements). But it also creates a much better environment for lens optics. For a given sensor hypotenuse, it requires a given iris diameter to provide a given realtive aperture. f2.0 means that the area of the shutter is 1/2 the area of the imaging sensor. The larger the sensor, the larger the diameter of the iris for a given f-stop. 4/3 cameras simply require smaller diameter irisses than other SLR sensor designs. That's why we find Oly making f 2.0 zoom lenses when other manufacturers are making similar EFL lenses at f2.8 or 3.5--to make them any faster, the physical diameter would be overwhelming.

But that's not the end of the story; the aspect ratio comes into play as well. A 4/3 camera has an aspect ratio (1.33:1) closer to a perfect square than an APS-C, APS, or full frame camera, which have an aspect ratio of 1.5:1. That means that a 4/3 lens can have a smaller diameter lens for a given iris diameter than a Canon or Nikon. Of course you CAN make a lens with a narrower diameter than what is ideal, but what you wind up with are optics with much more noticable aberations. All of this is why Zuiko lenses for Oly's are known to be outstanding opticaly. Nikon and Canon could make f 2.0 zoom lenses for full-frame cameras with distortion levels as low as Zuiko, but they'd have to be so much larger and heavier that they'd be too expensive and too heavy to handle, or be so expensive to grind that nobody could afford them.

So don't be so harsh on Oly and their camera's less than stellar signal to noise ratios under low light conditions, as there's something to be gained from this seeming loss. You'll feel it every time you hold your camera in your hands. At least that's why I enjoy my Oly--even when I need to shoot under low light conditions.

Damn, I was wordy. Sorry.

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