Why exactly do large sensors have more dynamic range

Started 3 months ago | Discussions thread
Erik Kaffehr
Erik Kaffehr Veteran Member • Posts: 5,825
Re: Why exactly do large sensors have more dynamic range

HDRI wrote:

JimKasson wrote:

HDRI wrote:

Many resources(websites) attribute the large sensors having more DR due to they having bigger pixels. But in current days , GFX100 has 3.75 µm pixel pitch and Sony A7Siii has 8.4 µm pixel pitch. And yet GFX100 has higher PDR than Sony by around 1.5 stops.

So what exactly makes larger sensors have more DR.

Or if a company wishes they can actually have FF sensor like A7Siii have more/same DR as GFX 100 but they don't so for some other marketing reasons ?

You're talking per-image DR, not per-pixel DR, right? Useful base-ISO DR these days is pretty much controlled by shot noise, not read noise. Signal to noise ratio of shot noise goes as the square root of the number of electrons counted. Full well capacity per unit area has maxxed out at around 3000 electrons per square micrometer (3000 e-/um^2).

The only useful way at present to get more FWC across the entire sensor is to make the sensor bigger.

One further question which I have on this is : since a scene can have bright areas and dark areas , does per image DR would actually be DR at pixel group level instead of single pixel , so that such multiple groups capture the luminance they are exposed to correctly ? And with current tech more pixels per area is gonna help more than single large pixel ?

Hi,

Larger pixels have a tiny advantage in DR comapred with smaller pixels over the same area.

Phase One used to have Sensor+ that bins four pixels in hardware at some ISO. Here you can see that binning four pixels at ISO 800 yields a gain in DR. But the much smaller pixels of a modern camera have a huge improvement in DR. The plots here are normalized to the same print size.

Source: DxO mark

Best regards

Erik

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Erik Kaffehr
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