Nex-7 vs EM5 Shutter Speed comparision at ISO 200

Started Apr 3, 2013 | Discussions thread
texinwien
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Re: Nex-7 vs EM5 Shutter Speed comparision at ISO 200
In reply to CosmoZooo, Apr 4, 2013

CosmoZooo wrote:

I wondered myself if the overstated ISO affect shutter speed on OMD to be slower then NEX.

No one has made a convincing case yet that suggests that it does. DPReview is the only credible source I've seen claim that it does, and that's by an amount allowed under the SOS method defined in the ISO specification. it's also a finding that isn't universally accepted as fact, AFAIK.

Even being an NEX owner I have to agree with folks who say not really at least in the example above:

I recently learned about this interesting, although very limited, site:

http://www.sensorgen.info/

Keep an eye out for bobn - he runs the site and posts at DPReview sometimes, also on the topic of ISO. If you pay attention to him, you'll learn that you've misunderstood some of the basics of the ISO issue.

So the truth is - Sony also overstates the ISO but perhaps less so then OMD - yet not enough so  for any significant gap between them - in this example

From the site:

Nex-7, stated ISO 200, measured ISO 159

OMD, stated ISO 200, measured ISO 107

So that's ISO diff of 52 which is highly insignificant as these shots actually prove.

Anyone arguing otherwise is ignoring the facts.

On the other hand and perhaps here comes the punch line as the ISO keeps going up the gap gets significantly larger:

This isn't the punchline. The absolute gap grows significantly, but the relative gap doesn't, and it's the relative gap at each of these measures that matters.

Nex-7, stated ISO 3200, measured ISO 2617

OMD, stated ISO 3200, measured ISO 1489

Diff is 1,128 ISO - how many stops is that - I haven't gotten the hang of those calcs yet

It is clear that you haven't gotten a hand of those calcs yet - the absolute differences at each stated ISO are uninteresting. It is only the relative differences that are interesting, and while they aren't static, they're pretty close to it.

And if we keep going:

Nex-7, stated ISO 12800, measured ISO 10702

OMD, stated ISO 12800, measured ISO 5953

Diff is 4749 ISO - how many stops is that?

Very close to the same amount of stops as at ISO 200 and ISO 3200. Here are the calcs, based on the numbers you provided here:

Stated | Sony Variance | Oly Variance | How many stops is that?

ISO 00200 | SV 0.80 | OV 0.54 | S 0.26
ISO 03200 | SV 0.82 | OV 0.47 | S 0.35
ISO 12800 | SV 0.84 | OV 0.47 | S 0.35

Don't shoot the messenger - I didn't come up with those numbers

No shooting, but some friendly advice that you have a lot to learn here, and it's a pretty complicated topic. Try to take your time, keep an open mind and not jump to conclusions while you're still figuring things out.

but to the original poster if you want to do a more effective test go up in ISO...start at 3200. If the site is correct there will be a measurable diff in the shutter speed then.

Perhaps, perhaps not. Neither sensorgen.info nor DxOMark's numbers say anything about camera metering. Additionally, I don't think the original poster is interested in the cameras' metering performance at ISO 3200. He's more of a bird, wildlife and action shooter, and I'm pretty sure he stays will under ISO 3200. I don't think he's here to prove a general point about metering. Rather, he's trying to find out whether there are any systematic differences in metering at the settings he would normally use. So far, he hasn't shown any compelling evidence of such differences in any significant amount.

tex

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