Dynamic Range of RAW digital sensor data

Gisle Hannemyr wrote:

I am looking for hard data on the dynamic
range of different digital sensors,

Unfortunately such hard data is not available unless you find the
manufacturer's data-sheet of the sensor. And if you do find such a
data-sheet then you must calculate the effect of photon shot noise in to
the specified properties since all the sensor manufacturers ignore the
photon shot noise totally.

Sensor manufacturers simply calculate the dynamic range as:
The full well capacity in electrons in divided by the noise electrons
that are induced by the sensor. This is the proper definition for many
other instrumentation but not for any instrumentation that measures
light (photons).

Light has the property called photon shot noise (also called as the
Poisson noise) and the quantity of this noise is the square of the
electrons (electrons are those photons that gets detected).

In photographic sense the sensor manufacturer's definition of the
dynamic range is the same as a shooting situation where an object
surface in the scene is captured by the camera in such way that the
camera records the surface at the maximum output level (255 in 8-bit/c
notation) but there is not a single photon reflecting from that surface
(so it appears to be absolutely black). Obviously such definition and
specification of the dynamic range is nonsense.

For example, the true dynamic range for a full well that has the
capacity of 50000 electron is sqrt(50000) or 223:1, due to the photon
shot noise. Those noises that the sensor manufacturers regard as noises
then decrease this further. In other words the true dynamic range of a
light sensing sensor can never be equal to the square root of the full
well capacity in electrons. It can be rather close to that in case the
sensor induced noises are very small (this is the case with actively
cooled sensors that are often used in scientific applications).

Not all that 233:1 dynamic range is usable since we do not accept such
image information as _useful image information_ that has signal to noise
ratio of sqrt(1) or 1:1.

E.g. at 16 electrons the signal to noise ratio is just 4:1 due to the
photon shot noise only, such image information looks _very_ bad, very
noisy. But if we do accept that then a sensor that has full well
capacity of 50000 electrons has _useful_ dynamic range of 233/4 or
58.25:1 or 5.9 f/stops only.

Now then, the task of measuring the dynamic range of a digital camera is
incredibly a difficult one.

One major error source are the internal reflections: Between the
individual lenses of the camera lens, between the blur-filter and the
surface of the exit lens of the camera lens, between the blur filter and
the sensor, and inside the sensor compartment.

These reflections create a more or less diffuse fog of light that adds
to the measurement so in the dark end the measurement will be way
incorrect. What happens is that when testing the dynamic range e.g.
using a Stouffer step wedge even the 3.0D patch _seems_ to get recorded,
the camera _seems_ to output some signal for the 3.0D patch but the
reality is that the signal is mostly from the fog. But people happily go
and announce that the dynamic range is more than 3.0D or more than
1000:1 or more than 9.966 f/stops. These reflections are one of the main
reasons for the incorrect/unrealistic high DR test results that can be
found on the Web.

An other major error source is the noise reduction, some of it is
performed already before the raw data is written. The noise reduction
has the effect that even if a camera seem to detect some signal for a
very dark, large, uniform patch of a step wedge, it can not deliver fine
structured image detail that reside at equally low luminance levels, the
noise reduction algorithms will clean such fine structured image detail
away. So, such signal is not inside the useful dynamic range of the
camera nor inside the true dynamic range of the camera. Unless the
camera is only used for recording such large uniform surface areas like
the patches of the step wedge.

Timo Autiokari

Timo Autiokari wrote:

Gisle Hannemyr wrote:

I am looking for hard data on the dynamic
range of different digital sensors,

Unfortunately such hard data is not available unless you find the
manufacturer's data-sheet of the sensor. And if you do find such a
data-sheet then you must calculate the effect of photon shot noise in to
the specified properties since all the sensor manufacturers ignore the
photon shot noise totally.

Wrong.
http://www.clarkvision.com/imagedeta...rmance.summary

several sensors analyzed at (and references to others):
http://www.clarkvision.com/imagedeta...ensor_analysis

Sensor manufacturers simply calculate the dynamic range as:
The full well capacity in electrons in divided by the noise electrons
that are induced by the sensor. This is the proper definition for many
other instrumentation but not for any instrumentation that measures
light (photons).

Wrong. It is the correct definition for light sensors and is
the definition used in the electronics industry.

Light has the property called photon shot noise (also called as the
Poisson noise) and the quantity of this noise is the square of the
electrons (electrons are those photons that gets detected).

Correct.

In photographic sense the sensor manufacturer's definition of the
dynamic range is the same as a shooting situation where an object
surface in the scene is captured by the camera in such way that the
camera records the surface at the maximum output level (255 in 8-bit/c
notation) but there is not a single photon reflecting from that surface
(so it appears to be absolutely black). Obviously such definition and
specification of the dynamic range is nonsense.

Wrong. You forget that 8-bit image data are gamma encoded.

For example, the true dynamic range for a full well that has the
capacity of 50000 electron is sqrt(50000) or 223:1, due to the photon
shot noise. Those noises that the sensor manufacturers regard as noises
then decrease this further. In other words the true dynamic range of a
light sensing sensor can never be equal to the square root of the full
well capacity in electrons. It can be rather close to that in case the
sensor induced noises are very small (this is the case with actively
cooled sensors that are often used in scientific applications).

Wrong. You confuse signal-to-noise ratio with dynamic range.

Not all that 233:1 dynamic range is usable since we do not accept such
image information as _useful image information_ that has signal to noise
ratio of sqrt(1) or 1:1.

Wrong.

E.g. at 16 electrons the signal to noise ratio is just 4:1 due to the
photon shot noise only, such image information looks _very_ bad, very
noisy. But if we do accept that then a sensor that has full well
capacity of 50000 electrons has _useful_ dynamic range of 233/4 or
58.25:1 or 5.9 f/stops only.

Wrong.

Now then, the task of measuring the dynamic range of a digital camera is
incredibly a difficult one.

No it is not if you have access to the raw data.

One major error source are the internal reflections: Between the
individual lenses of the camera lens, between the blur-filter and the
surface of the exit lens of the camera lens, between the blur filter and
the sensor, and inside the sensor compartment.

If you use correct methods, none of the above are problems.
Follow the procedures here, which is the industry standard
method for measuring properties:

Procedures for Evaluating Digital Camera
Sensor Noise, Dynamic Range, and Full Well Capacities;
Canon 1D Mark II Analysis
http://www.clarkvision.com/imagedetail/evaluation-1d2

These reflections create a more or less diffuse fog of light that adds
to the measurement so in the dark end the measurement will be way
incorrect. What happens is that when testing the dynamic range e.g.
using a Stouffer step wedge even the 3.0D patch _seems_ to get recorded,
the camera _seems_ to output some signal for the 3.0D patch but the
reality is that the signal is mostly from the fog. But people happily go
and announce that the dynamic range is more than 3.0D or more than
1000:1 or more than 9.966 f/stops. These reflections are one of the main
reasons for the incorrect/unrealistic high DR test results that can be
found on the Web.

An other major error source is the noise reduction, some of it is
performed already before the raw data is written. The noise reduction
has the effect that even if a camera seem to detect some signal for a
very dark, large, uniform patch of a step wedge, it can not deliver fine
structured image detail that reside at equally low luminance levels, the
noise reduction algorithms will clean such fine structured image detail
away. So, such signal is not inside the useful dynamic range of the
camera nor inside the true dynamic range of the camera. Unless the
camera is only used for recording such large uniform surface areas like
the patches of the step wedge.

Timo Autiokari

I suggest more research before you post again, and then if
you don't change, be prepared to tell why the entire
electronics industry and scientists are wrong and you
are right. There is a Nobel prize waiting.

Roger