Confused by "equivalency" and ISO for low light

Started 4 months ago | Discussions thread
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Confused by "equivalency" and ISO for low light
4 months ago

To provide some background for my question, my goal is to take handheld, flashless, indoor snapshots (I distinguish this from photographs) of (slow moving) family, friends, and pets for the sake of capturing memories. I recently bought a Panasonic G6 (w/kit lens) with the intent of fulfilling that purpose, but I'm disappointed with the results. I can't seem to get decent low-light exposures above 1/15" (many end up much slower), and as a result, many of them are blurred, due both to moving subjects and camera shake. If I dial up the shutter speed, either I can't get a decent exposure at all, or it ends up at (ISO 6400 or higher) and the results look terrible. I've considered adding a brighter lens, but all of the m43 primes are unstabilized, which would seem to worsen my problem of blurred pictures.

So I'm trying to understand WHY I can't get a faster shutter speed in low-light, and more specifically, what I would need in order to get it. Enter the world of equivalency. I understand the concept, and I understand crop factor and how it relates to zoom level. I understand stops and aperture. But where I think I'm getting lost is with ISO, and how equivalency interplays with it.

Basically I'm trying to assess how other cameras would handle low light in relation to mine. Let me start with the specific comparison of my Panasonic G6 with a Panasonic LX7. My G6 has a minimum aperture of f/3.5, whereas the LX7 has f/1.4. But the G6 has a larger sensor: m43 to the LX7's 1/1.7". As far as I can tell the crop factors are G6=2, LX7=5.1 (if this is wrong please let me know).

So does this mean the G6 has an equivalent minimum aperture of 3.5*2 = f/7, and the LX7 a minimum equivalent aperture of 1.4*5.1 = f/7.1? If so, that tells me they're comparable in terms of minimum equivalent aperture. But what I don't understand is how ISO factors into this. If I want the same shutter speed for both, would I have to use the same ISO for both? Or would the faster lens on the LX7 allow me to use a lower ISO (despite the fact that the equivalent apertures are the same)? Which one of these is likely to perform better in low light, and why?

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Panasonic Lumix DMC-G6 Panasonic Lumix DMC-LX7
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