What is equivalence good for?

Started Jul 25, 2014 | Discussions thread
quezra Veteran Member • Posts: 3,915
Re: What is equivalence good for?

JBurnett wrote:

quezra wrote:

6. You want to buy a nice camera with good lowlight options. You're trying to decide between an LX7 (f/1.4-2.3 lens), RX100 (f/1.8-2.8 lens), GM1 (f/3.5-5.6 lens), and A5000 (f/3.5-5.6 lens). You decide the LX7 is the best because f/1.4 = f/1.4 = f/1.4

So, what's low light? And what is my intended output -- web only, 13 x 19" print? This is where it gets more difficult.

PERSONALLY, I would try to come at this from a KNOWN comparison point. For my purposes that means "how does it compare to my G3 Micro-4/3 camera shooting at f/2 and ISO 1600, with a 90mm-equivalent lens". You see, this is real-world for me, shooting musical performances in lower-lit venues at that focal-length. (Shooting f/2 and ISO 1600 might also be good settings for people pics in my kitchen using the overhead lights.)

Well, first I would look at the ISO needed to shoot each camera wide open at as close to 90mm as the camera can get. Then I would look at the camera's IQ and noise at that ISO (if available).

So the LX7 needs to be shot at f/2.3 and ISO somewhere between 1600 and 3200. Looking at the LX7's IQ at ISO 1600, I would rule out this camera for shooting what I do now.

The RX100 iii needs to be shot at f/2.8 and ISO 3200. Now, Sony does a great job with this little sensor, but I would also rule this camera out.

GM1. Well, I wouldn't use that lens, of course, but if I HAD to, I'd have to shoot at ISO 12800. No way. If I changed to the same lens as I use on my G3 and shot at ISO 1600, the newer sensor in the GM1 would give me slightly better results.

A5000. Similar story. Change lenses to 50mm f/1.8 and get better low-light performance than I'm getting now. Or shoot at f/5.6 and ISO 12800 with the kit lens and... nah, that won't work.

So it's the GM1 or A5000 with 50mm f/1.8. But wait, I want (no, NEED) an EVF. Oh, oh. Deal breaker. No problem, I didn't like the handling of either of them anyway.

Of course, low light to someone else might be something different. And if they're not shooting people and can rely on image stabilization for slower shutter speeds, then high-ISO noise may be less of an issue. For example, I have some quite nice 8 x 10 pics from inside a church (without people) taken with a Canon G9 at ISO 400 and 1/15 sec. handheld.

One you're generally subscribing to the notion of equivalence and I have no problem with that.

Two you've also introduced additional requirements that aren't mine.  I am looking at a bunch of compacts on a limited budget that won't require specialist lenses.

The point is to show that equivalence is useful.  The funny thing is all these interventions subscribing to some degree of equivalence thinking while tossing in lots of red herrings to try to make it sound as if equivalence isn't really about equivalence.

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