The Eyes Have It
By Michael Reichmann
On Sunday, June 15th I published my review of the new Sony A7s. With regard to the camera's dynamic range, and Sony's claim of 15 stops of DR, I wrote...
"Based on these tests as well as my day-to-day shooting I do not see any obvious difference
in dynamic range between the two camera. Many people had speculated that the larger pixels
of the A7s would produce wider dynamic range capability. Not that I can detect. It will take someone
with a full testing lab to determine if there is any gain in DR or not, but I don't see it'.
This did not sit well with some people. I must be blind, they wrote, or worse.
But, when I test equipment I do something that puzzles some people – I trust my eyes. I may not be the world's finest observer, but decades as a photographer, teacher, writer and reviewer have given me some ability to judge image quality. I don't have a sensor test bench, but I just didn't see any advantage in terms of DR to the 12 Megapixel A7s over the 36 Megapixel A7r.
Then, two days later on Tuesday, June 17, DxO Labs, who does have a rather nifty sensor testing lab, published their test results on the A7s, and anyone can call up a comparison with any other tested camera. Such a comparison with the A7r is shown below.
As can be seen, DxO rates the A7s as having 13.2 stops of dynamic range while the A7r has 14.1 stops. Not a huge margin for the A7r, but noticeable.
Marketing vs. Reality
At issue here as well is that when Sony claims 15 stops of dynamic range they don't say what their test criteria are. And since there are no standards for DR testing, a comparison can therefore only be regarded as apples and oranges.
On the other hand, the DxO numbers, whether you believe them in an absolute sense or not, are relative to the hundreds of cameras that DxO have tested over the years.
I won't belabor the point. Sony claims 15 stops, and based on their internal criteria they may be correct. I have no reason to doubt their veracity. But, a lot of photographers hung their hats on this claim, and dissed me for not seeing it.
Now we see that based on a self-consistent third party test, the A7s does not have better DR than the A7r, and indeed has lower DR by almost a full EV. The absolute number isn't important. At least 30 other cameras in the DxO database have better DR scores than the A7s.
I should also point out that when it comes to high ISO performance the A7s is #1 in DxO's ranking, but not by as huge a margin as one would imagine.
One More Thing
I normally don't comment on what's said on other web sites, but the site Petapixel wrote in a headline "Report Claims the Sony A7s’ Image Quality is Comparable to Medium Format". Well, actually no. That's not what I wrote. Rather, what I wrote in part was... "There is something to the look of A7s files that reminds me of medium format..." . Quite a difference, don't you think?
Oh well, at least they spelled my name right.