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

Started Apr 29, 2013 | Discussions thread
2eyesee
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Re: How to properly compare RX-100 and NEX-6 kit high ISO noise?
In reply to CosmoZooo, May 1, 2013

CosmoZooo wrote:

Allright 2eyesee let's have that discussion:

First of you're preaching to the choir: I perfectly understand that NEX is APS-C sensor but not only you're arguing semantics - you're just incorrect in a number of ways in your assessment of that sensor advantage. "Better" is a very general word which in this case implies many characteristics such as size, DR, ISO performance etc. which is a much better way to characterize the advantage of the NEX-5R sensor over RX100 then larger.

We all know that APS-C sensor performance is not the same across all APS-C size sensors...you see where I am going with this. Sony sensors are some of the best ones right now. It is not that the sensor gathers more light overall because that simply implies a larger area: each of the photo sensitive sites on that sensors that correspond to pixels perform better - each one gathers more light then the equivalent pixels on RX100. That is one misconception in your statement.

The individual photosite size is not so relevant on modern sensors with gapless pixels - it's the total amount of light gathered by the lens that's the most important factor in determining noise levels/DR. I'm no expert but I have been corrected on this in another thread and upon further investigation it seems to be true for modern sensors.

Second is your pointless math which would imply that every APS-C size sensor would have a 1.66 stops advantage over RX100 which is obviously false. There are many APS-C sensors that do not perform nearly as well as NEX sensors and would not carry the same advantage over RX100 as NEX. Even NEX-7 which packs more pixels onto the sensor would not carry the same advantage as NEX-5R sensor. Just think about the sensor scores on the DXOmark RX100 scores close to 400 on the ISO while NEX-5R almost 1000. Again not just the sensor size that matters here.

My math was not pointless, but it was a gross over-simplification as a comparison as it was only dealing with the light-gathering capabilities of the RX100 vs NEX with kit lens, not sensor performance.

Which brings us to your third misconception about assigning a static value to the sensor advantage.    ISO performance is not necessarily linear if you look at DXO graphs as such the stop advantage could become even larger as the two sensors continue to push up the ISO scale. And the number you quantified is definitely meaningless because you based it on the size rather then actual sensor performance.

Theoretically speaking the small sensors of tomorrow may outperform the large sensors of today. Of course their larger counterparts will still keep the lead but my point here that ultimately its sensor performance that matters not sensor size which may or may not be a factor depending on which sensors are being compared.

I wasn't talking about sensor size - I was talking about the light gathering capabilities of each system, which will be a huge factor in determining image quality. And as my math showed a small sensor with fast lens (at least wide on the RX100) can be at an advantage over a large sensor with a slow lens.

Of course it doesn't take into account lens quality and sensor performance, but it's a worthwhile exercise to see how much light each sensor has to work with.

Even though my math was an over-simplification, it's interesting to note it essentially agrees with your first post on this thread:

"I'd say even comparing kit for kit NEX-6 wins overall, IMO...unless we are talking specifically at their lowest focal lengths at which RX100 has a slight lead."

For example the RX100 may already outperform or come extremely close to some of the significantly larger m43 sensors from previous generations.

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