FZ28: sensor, lens and EZ zoom

Started Apr 30, 2009 | Discussions thread
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Ianperegian
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FZ28: sensor, lens and EZ zoom
Apr 30, 2009

FZ28: sensor, lens and EZ zoom

There has been some recent discussion about the way EZ zoom works in relation to the sensor and the lens on the FZ28. I'd like to offer my understanding of it to get feedback from the experts here to see if I'm correct - shoot me down if you will :-))

When you make the opening of the aperture on the FZ28 smaller in size than its full aperture, say setting it from f/2.8 to f/4, then you are physically covering up the outer part of the lens area. You can set the cam (set to 10MP) to manual exposure (M) and set the aperture to f/2.8 and the shutter speed so that it gives the correct exposure with the shutter button half-pressed. Then you can watch the image on the EVF/LCD while you change the aperture to f/4 and half-press the shutter button again. You will see that no part of the scene is lost, but instead, the image just becomes darker overall. That is because because less light is getting through the lens, but the effect (the darkening) is uniform. The important thing is that every point on the image becomes darker.

I think this demonstrates in a simple way that all of the lens area is involved with producing every part of the image. In other words there is not a central part of the lens that is "dedicated" to creating the image on the centre part of the sensor. Similarly there is not an outer part of the lens that contributes only to the outer part of the image. The inner and outer parts of the lens, and all parts in between, all contribute to every part of the image.

So, when you take an EZ zoom shot, the cam is cropping from the central part of the sensor but all of the lens area (at that f stop) is still contributing to the image. It is not the case that the EZ zoom image has some special centre part of the lens associated with it.

A more technical version is given at: http://en.wikipedia.org/wiki/Lens_ (optics) under the subsection on image formation from a converging lens.

Cheers,
Ian
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Ianperegian

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