Olympus OM-D (EM-5) comparison samples are now.. (continued)

Started Mar 17, 2012 | Discussions thread
John Carson Veteran Member • Posts: 4,253
Confused reasoning...

Bilgy_no1 wrote:

Raist3d wrote:

Continued to answer Andy Westlake:

Raist3d wrote:
Andy Westlake wrote:

A> How does the lighting intensity affect the high ISO noise?

R> If the camera compensates for the exposure with different shutter speed it sure can! A capture of the same final intensity under a longer exposure accumulates more noise.

So, the E-M5 is actually at a disadvantage. Less sensitivity means longer exposure means more noise? How does this prove that Olympus are cheating?

The passage you are quoting refers to variations in lighting, not variations in the reporting of ISO values. Here is what is being said

  1. Holding aperture and ISO constant, lower light means longer exposures are necessary to compensate for the lower light, and these longer exposures (marginally) increases noise.

  2. Holding aperture, reported ISO and lighting constant, overstated ISOs will mean longer exposures are necessary to compensate for the lack of gain being applied to the signal, and these longer exposures mean more light is being received by the sensor, which reduces noise (or, more precisely, boosts the signal to noise ratio).

To state the second point more simply, if you are overstating ISOs, then you are "really" shooting at a lower ISO than claimed and this, as everyone knows, gives less noisy images.

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john carson

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