Does higher sensor resolution change exposure or raw pixel values?
Asked 12/15/2016
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I tested two image sensors with the same 6 ms exposure time and the same set of lenses. For the same targets, the lower-resolution sensor gives higher raw DN values, while the higher-resolution sensor gives lower values.
Can spatial resolution itself affect the measured pixel values? For example, if a higher-resolution sensor has more, smaller pixels, are the incoming photons effectively spread across more pixels so each pixel records a lower DN value, even though the exposure settings are the same?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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It all depends upon how one defines exposure. If one defines exposure as the total number of photons captured per pixel then pixel density will most definitely affect exposure.
But in photography exposure is normally expressed in terms of field density. That is, in terms of photons per area unit of the film or sensor's surface. When the raw sensor data is used to create a viewable image the number of photons measured per pixel is normalized to account for the varying sizes of pixel wells (more properly called sensels) in much the same way that the brightness of prints of various sizes from the same negative are normalized so that a print with twice the surface area of another print from the same negative does not wind up being half as bright.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
9y ago
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Generated from our catalog & community — verify before relying on it.
Yes—if you compare raw per-pixel values, sensor resolution can affect the DN you measure.
In photography, exposure usually means the amount of light per unit area reaching the sensor, not the number of photons collected by each individual pixel. If two sensors receive the same light for the same time, the exposure on the sensor surface can be the same even though the raw pixel values differ.
A lower-resolution sensor often has larger pixels, so each pixel collects light from a larger area and can record a higher DN. A higher-resolution sensor often has smaller pixels, so the same total light is divided among more pixels, and each pixel may show a lower DN.
When creating a final image, this is normally normalized so brightness appears comparable despite different pixel sizes. So spatial resolution does not inherently change exposure in the photographic sense, but it can change raw per-pixel signal levels.
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