How to properly compare RX-100 and NEX-6 kit high ISO noise?

Started Apr 29, 2013 | Discussions thread
2eyesee
Contributing MemberPosts: 942
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Re: How to properly compare RX-100 and NEX-6 kit high ISO noise?
In reply to CosmoZooo, 11 months ago

CosmoZooo wrote:

That logic is only relevant to DOF calculation not light gathering ability which is what this discussion is centered around.

If you perceive the multiplier as relevant to the effective lens speed or brightness as some refer that is an incorrect logic and one I have fallen for in the past. If you look at my previous post, you will find a link to that discussion. As far as light gathering ability per pixel f1.8 is indeed f1.8 and f3.5 is still that. NEX compensates by having a better sensor but the actual lens is faster on the RX100 across the entire range, but aside from the smallest focal lengh the NEX kit plus APS-C combo will be better.

It's not that the NEX 'compensates by having a better sensor' - it's just that the NEX has a much larger sensor so it can gather more light, which compensates for it's slower lens.

Sensor sizes:

RX100
13.2mm x 8.8mm = 116.2 mm squared

NEX-6
23.5 x 15.6 mm = 366.6 mm squared

The NEX-6 sensor is therefore 3.2x larger than the RX100 sensor so gathers 3.2x the amount of light - which is around 1.66 stops.

At its widest focal length, the RX100 is around 2 stops faster then the NEX with kit lens (f/1.8 vs f/3.5), but as the NEX sensor gathers 1.66 stops more light this leaves the RX100 with a 1/3 stop advantage.

At the tele end, the RX100 is around 0.4 stops faster than the NEX with kit lens (f/4.9 vs f/5.6), but again as the NEX gathers 1.66 stops more light this leaves the NEX with the advantage this time of around 1.3 stops.

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