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...can actually get worse the faster a lens is.
I have the Canon 85mm F1.2 II. It is great at F1.2, but the edges of photos are quite dark (when used on a full -frame body). Stop it down to F3 and the vignetting is totally gone.
The size of the objective is one of the critical factors affecting vignetting. It's like having an inappropriately sized lens hood, but very out of focus (as you might imagine for a fast lens).
Fast lenses generally are sharper where telescopic resolving power is needed (which does not apply to this camera). The effects of diffraction (blurring) at the telephoto end for compact hyperzoom (> x20) cameras are testament to that.
For this camera, the limited wideangle/telephoto range and small imager may render vignetting insignificant.
However, vignetting can actually be beneficial...
further to what Ball Boy wrote...
the 'faster' the lens the larger the aperture, i.e. more light getting in, hence faster AF (if it goes through the lens) and shorter shutter times. a larger aperture also means a narrower depth of field, which makes everything that is not focused blurred ('background defocus' as the TV ads say). A smaller aperture means a larger depth of field, which makes everything in the frame sharper. Neither of these is better than the other. It's up to the photographer which he wants to use. Though a narrow depth of field is generally harder to work with.
Hence to get a sharper image on a wider aperture, you're actually relying on the quality of the optics.
Bring back the blue door! And I miss the cathedral.
That's 5.2mm f/1.8 actually. The equivalent aperture on 35mm full frame is f/8.2, and f/5.5 on APS-C. There really is no getting around the laws of physics.
F1.8? So 10 years ago!
10 years ago my Olympus Camedia 3040Z 3.3MP compact had (well, still has) a 1.8 lens so Samsung's claim for fastest lens on a compact is false. I'm not bashing the Samsung cam but apart from the pixel count and better shutter delays today's cameras are offering nothing new it seems.
The Olympus XZ-1 will be the serious compact yardstick when it's released, I reckon. Seems to take the best aspects of all its compact peers, and roll them into something pretty darned hard to resist.
Olympus are in general rather an unsung hero in the digital photography world, but now they've got a bit more attention with the Pen range, there's hope this might enjoy the success it should deserve.