Birders' Superzoom

Started Jul 20, 2012 | Discussions thread
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Stephen Barrett Contributing Member • Posts: 683
Birders' Superzoom


The angular resolution of SLRs is limited by their sensors whereas that of superzooms like the Canon SX40 is limited mainly by the lens. That is to say, the sensor retains most of the resolution that the lens achieves. For the Panasonic FZ200 with its shorter focal length and larger aperture, however, it is again mainly the sensor that limits the angular resolution. By my rough calculations, the Panasonic FZ200 will have caught up to the the SX40 in terms of resolution although you will have to crop more. Will the FZ200 become the birders' camera of choice? Sony and Nikon use more pixels but it takes a lot of pixels to significantly improve resolution and the smaller pixels work against image quality. For the next Canon superzoom to keep up with the speed and IQ of the FZ200, it too will require a larger-diameter aperture. By copying the FZ200's diameter of 38.57 mm (Possibility A), it will also achieve f/2.8 at 600 mm (plus f/3.9 at 840 mm, which is still wonderful). By increasing the diameter further to 44.7 mm (Possibility B), f/2.4 could be achieved at 600 mm, f/3.4 at 840 mm and f/4.0 at 1000 mm. With these larger apertures, the image reaching the sensor is still relatively sharp and it is mainly the sensor that limits the angular resolution. In this situation, the total angular resolution of the camera benefits from the longer focal length because the larger image on the sensor is spread over more pixels.

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Aperture Diameter ------------ Focal Length ------- f-Number

SX40HS-----------25.95-------------------------150.5 (840 equiv)--------5.8
FZ200-------------38.57-------------------------108 (600 equiv)----------2.8


A-------------------38.57-------------------------108 (600 equiv)----------2.8
-------------------------------------and-----------150.5 (840 equiv)-------3.9

B--------------------44.7-------------------------108 (600 equiv)----------2.4
--------------------------------------and----------150.5 (840 equiv)-------3.4
--------------------------------------and----------179.2 (1000 equiv)------4.0

Image Quality

Larger aperture is good for speed, image quality and resolution, so it is exciting to see things moving in that direction. The Fuji X-S1 moved in the direction of larger sensor size, which should be good for image quality but not for resolution at long focal lengths. SLR lenses keep IQ high partly by limiting the zoom range, generally to less than 10x. It is close to impossible to avoid chromatic aberration at the ends of a 35x zoom range. Wouldn't it be nice if Canon were to make a birder's superzoom with 100-1000 mm zoom with f/4 at the long end (like "possibility B" above)! Or maybe have two lenses, each with approximately 7x zoom, say 20-150 mm and 150-1000 mm. Now I'm just being greedy.

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