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

Started Apr 6, 2013 | Discussions thread
Erik Ohlson
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Re: LX7 DOES have a have a faster lens. ƒ1.4 is faster than ƒ1.8, sorry.
In reply to ultimitsu, Apr 7, 2013

ultimitsu wrote:

kkardster wrote:

The sensor specs favor the RX100 but the brighter and sharper LX7 lens often makes up for its lesser sensor.

This is a common misconception.

LX7 does not have a faster lens.

LX7's lens is 4.7mm F1.4, aperture is 3.6mm in diameter, actual opening is 10.2mm2

RX100's lens is 10mm F1.8, aperture is 5.6mm in diameter, actual opening is 24.6mm2

RX100's lens lets in 150% more light. it is much much brighter.

If the figures you give, above are the correct figures:

LX7 - ƒ1.4

RX100 - ƒ1.8

ƒ1.4 is bigger than ƒ1,8 just as ƒ2 is bigger than ƒ4.5, sorry.

Then the LX7 IS brighter. Don't get hung up on the diameter of the hole ƒ-numbers are RATIO of opening to focal length, it doesn't matter a hoot how big the 'hole' is, the aperture is a mathematical RATIO, and the bigger that number the less light is projected at that focal length.

For instance, the 6-inch diameter telescope I built from scratch (ground and polished the mirror) some 60 years ago was - yes - 6 inches in diameter ("the 'hole') but over 36 inches focal length and it worked out to about F11 "wide open".

The 200-inch diameter telescope on Mt. Wilson, 200 inches in diameter, has a prime focal length of 55.5 feet & that works out to ƒ3.3 - (same as my ZS19 ) - with that 200 inch "hole".

-Erik

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