LX7 - does its IQ compete with e.g. Sony RX100?

Started Apr 6, 2013 | Discussions thread
Cyril Catt
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Re: LX7 - does its IQ compete with e.g. Sony RX100?
In reply to ultimitsu, Apr 8, 2013

Ultimitsu and Erik Ohlson appear to be arguing at cross purposes. An English language dictionary will indeed define an aperture as an opening, hole, gap, or cleft, etc. But a photographic dictionary will define it more strictly, as a [Limiting] Aperture; [Effective] Aperture; [Relative] Aperture; or [Numerical] Aperture. It may also define an Aperture Ratio.

The most common use of “aperture” in photography is the “Relative” aperture, defined as the ratio of the focal length of the lens to the diameter of the “Effective” aperture (i.e. the diameter of a circle of area equal to the area of the actual aperture - if it is not a circle). It is this “Relative” aperture which is referred to in the commonly used “f number” terms  - f1.4, f2.0, f2.8, etc -  which define the light-passing power of a lens.

Other things being equal, camera lenses of different focal lengths and different effective apertures form an image of the same brightness on the film or sensor if their relative aperture (or f number) is the same. But an f1.4 lens WILL form a brighter image than an f1.8 lens.

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Cyril

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