Scanners are subject to the same saturation:noise criterion as for dynamic range in digital cameras, except it is instead described in terms of density (D). Depending on the application, each unit f-stop may also be described as a "zone" or "eV." SCANNERS A contrast ratio of 1024:1 could therefore also be described as having a dynamic range of 10 f-stops (since 2 10 = 1024). The most commonly used unit for measuring dynamic range in digital cameras is the f-stop, which describes total light range by powers of 2. Overall, the dynamic range of a digital camera can therefore be described as the ratio of maximum light intensity measurable (at pixel saturation), to minimum light intensity measurable (above read-out noise). Total noise represents the sum of photon noise and read-out noise. Photon noise is created by the statistical variation in arrival of photons, and therefore represents a theoretical minimum for noise. Techncal Note: Even if a photosite could count individual photons, it would still be limited by photon noise.
#F STOP IN PHOTOGRAPHY ISO#
Therefore, dynamic range generally increases for lower ISO speeds and cameras with less measurement noise. The black level is limited by how accurately each photosite can be measured, and is therefore limited in darkness by image noise. Dynamic range is therefore limited by the darkest tone where texture can no longer be discerned we call this the black level. In reality, consumer cameras cannot count individual photons.
An example of this is many of the Canon cameras, which have an ISO-50 speed below the ordinary ISO-100.
#F STOP IN PHOTOGRAPHY FULL#
This is because the setting in effect overexposes the image by a full f-stop, but then later truncates the highlights - thereby increasing the light signal. Technical Note: In some digital cameras, there is an extended low ISO setting which produces less noise, but also decreases dynamic range. Since larger photosites can contain a greater range of photons, dynamic range is generally higher for digital SLR cameras compared to compact cameras (due to larger pixel sizes). If each held 1000 photons, then the contrast ratio would be 1000:1. For an ideal camera, its contrast ratio would therefore be just the number of photons it could contain within each photosite, divided by the darkest measurable light intensity (one photon). A photosite which overflows is said to have become saturated, and is therefore unable to discern between additional incoming photons - thereby defining the camera's white level. Therefore, if the bucket becomes too full, it will overflow.
Photosites can be thought of as buckets which hold photons as if they were water. Darker White Level (Low Capacity Photosite)
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