Автор: tantris
Дата: 23-02-10 18:20
nycandre wrote:
Canon 1DM4 and D3 equal in low light performance?
I seriously doubt it - Canon would have trumpeted its high ISO advances - I'll trust my other sources which by the way are confirmed by the DxOMark high ISO performance ratings - and the do have a scientific method to rate cameras.
DxO marks: Canon 1D MarkIV: 1320 Nikon D3/D700: 2300 Nikon D3S: 3250
This, as usual, proves that it's critical to look past the headline 'DxOMark' and look at the actual data. If you do this, a different story emerges.
First of all, let's look at what DxOMark's 'Low light ISO' score actually represents. If you delve into the site and read the description, you'll see it's an either/or parameter that tries to balance 18% grey noise with dynamic range. In reality, though, because of the choice of cut-off points, in practice with DSLRs it effectively becomes a measure of 18% grey noise (which almost always cuts off sooner). Technically this is (roughly) a product of sensor size and quantum efficiency, and due substantially of the 1D IV's smaller sensor, it loses out by about a stop.
The problem is, though, that visually, when looking at actual pictures rather than raw sensor data, high ISO image quality tends to be limited much more by shadow noise than 18% grey noise. In DxO-speak, this is represented by the dynamic range tab. If you look at that, the 1D IV's line crosses over the D3's at 1600, giving slightly higher DR (i.e. lower shadow noise) at high ISOs. This is completely consistent with our review - the 1D IV is essentially capable of matching the previous champion. (Throw the D3S into the ring, though,and you can see the improvements Nikon has made.)
The scientific method is all very well, but you absolutely have to understand what assumptions are going on behind the presentation of that data, and what effect they have on the headline scores.
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