Moon Maid's sensor comparison (PART 2)

Started Mar 1, 2012 | Discussions thread
MOD Marianne Oelund Veteran Member • Posts: 7,818
DR "immunity" from ISO increase

Horshack wrote:

This article looks like a description of unity gain, unless I'm missing something.

Think of it as showing how well the camera avoids losing DR as ISO is raised.

Three important cases:

1. Flat (e.g. D7000)

Read noise scales directly with ISO and DR falls about 1 stop for each stop increase in ISO, thus the "ISO-less" character. One comment I have, is that for comparison purposes, it would be better to show these cameras as flat at 1 instead of 0, for example.

2. Low-range immunity (e.g. D3)

Read noise rises very little from base ISO, until about ISO 800. This keeps DR from falling over that range. Above ISO 800, read noise scales with ISO. Compared to case 1, though, this type of camera starts with lower DR at base ISO, so it's really just recovering a deficit.

3. Wide-range immunity (e.g. D3s, D4)

Same as case 2 up to ISO 800, but then some optimization is seen, so that read noise rises more slowly than ISO. This results in preserving about an additional stop of DR by ISO 12800.

The D800 is a milder example of this case, with read noise rising more slowly than ISO, but only up to ISO 1600. The optimization gives the D800 about an extra 2/3 stop of DR above what it would have had at ISO 1600 without optimization.

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