The Economist article on mirrorless cameras

Started 6 months ago | Discussions thread
Jerry Fusselman
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Answer 2
In reply to Erik Magnuson, 6 months ago

Erik Magnuson wrote:

Jerry Fusselman wrote:

Yes, I looked at the five curves under the Measurements tab, and all five matter, but I didn't want to get bogged down in so much detail. Any subset of that detail can look like cherry picking.

But looking at these graphs, do they support your statement "According to DXOmark, the a7r sensor already beats every Canon camera (I own mostly Canon equipment) in low-light ISO performance." Four performance graphs at the ISO 1600 line:

  • SNR18%: too close to call where it crosses the 1600 line.
  • DR: The 6D is slightly higher where it crosses the 1600 line.
  • Tonal Range: too close to call but the A7R may be a tiny bit higher.
  • Color Sensitivity: At the 1600 line, Sony about 1-bit higher.

So you look at that and say "beats?" On the right side of the, DxO attempts to indicate the visual significance of those numbers with a color scale. Are any of the differences visually significant? Remember also that this is purely based on the raw data not including a converter. Can you get these same differences (or more or less difference) using your toolchain of choice?

I don't plan to quibble on what beats means except to say that higher is better in these cases.  Win a marathon by 0.01 seconds and you still won.  You still beat the other guy.

I'm not going to get into "significance" or any of that ugly NHST nonsense.  Objectively better is better, and I was mainly trying to show that Sony's best sensor is *not inferior* to Canon's best in low light.  It is icing on the cake for it to be higher when told it surely must be much lower (and not going to catch up even in three years), even if higher by just a smidgen.

But there are two things you left out of your analysis that ought to relate to "significance," if you want to see a gap between the two in low-light performance.  First, that 1-bit superiority in color depth is surely significant:  It equals the standard improvement in color depth that you get when going from ISO 200 to ISO 100.  That's plenty visible for many subjects.

Second, the low-light ISO score takes into account several issues not in the five curves you like so much, and combining all of these aspects gives the A7r a score of 2746 vs. the 5D M3's 2293, which might be noticeable.

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Jerry Fusselman

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