Could you actually see photos made from RAW files?

On Sat, 06 Jun 2009 20:29:27 +1000, Bob Larter
wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 14:45:53 +1000, Bob Larter
wrote:

Well, Eric's correct to say that at a quantum level, you're dealing with
integer numbers of photons & electrons, but he's missing the important
point, which is that an image sensor doesn't have any way of 'counting'
anything, & that the output voltage is merely an approximation of the
input signal.

Which is then digitised to the necessary level of accuracy by
comparison with a ramp signal.

You're thinking of dual-slope conversion, as used in multimeters & the
like. Dual-slope is very, very slow. For this sort of application (ie;
fast) you either use a flash converter or a fast SAR converter.

Eg; something like this:
http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad9254/products/product.html
(Note that they aren't cheap.)

Its too long since I was involved with anything like this but as far
as I can see these all work by constructing a reference ramp signal
(not necessarily linear) comprised of individual reference voltages
with which to compare the input.

You may use http://en.wikipedia.org/wiki/Analog-...ital_converter
to define the limits of my understanding. :-)



Eric Stevens

On Sat, 06 Jun 2009 03:10:45 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 14:45:53 +1000, Bob Larter
wrote:

Well, Eric's correct to say that at a quantum level, you're dealing with
integer numbers of photons & electrons, but he's missing the important
point, which is that an image sensor doesn't have any way of 'counting'
anything, & that the output voltage is merely an approximation of the
input signal.

Which is then digitised to the necessary level of accuracy by
comparison with a ramp signal.

Comparison witha reamp signal???

You've been doing some research, and now the whole concept of
digital voltmeters is confusing you just as much as are digital
cameras!

Yeah. I did some research, way back in the mid 1960s. I did more with
the introduction of digital music (whenever that was). So I do have
some idea of what I am talking about.



Eric Stevens

Eric Stevens wrote:
On Sat, 06 Jun 2009 03:02:16 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Fri, 05 Jun 2009 16:27:15 -0800, (Floyd L.
Davidson) wrote:
Or instead of your search on "voltage +quantization" (which gets
only 276,000 hits), try "voltage +analog" for 10 million hits.

Its only a list of searches relating to the problems of the
quantization of voltage.

Right, now do you understand what you just said?

The problems associated with the process of quatization of
voltage. Which means that voltage is analog, and there
are processes used to quantize it.

Duh!

You original assertion is there for a "Duh!"

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Eric Stevens wrote:
On Sat, 06 Jun 2009 03:10:45 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 14:45:53 +1000, Bob Larter
wrote:

Well, Eric's correct to say that at a quantum level, you're dealing with
integer numbers of photons & electrons, but he's missing the important
point, which is that an image sensor doesn't have any way of 'counting'
anything, & that the output voltage is merely an approximation of the
input signal.

Which is then digitised to the necessary level of accuracy by
comparison with a ramp signal.

Comparison witha reamp signal???

You've been doing some research, and now the whole concept of
digital voltmeters is confusing you just as much as are digital
cameras!

Yeah. I did some research, way back in the mid 1960s. I did more with
the introduction of digital music (whenever that was). So I do have
some idea of what I am talking about.

I'm glad you told us that Eric, because it was not apparent
otherwise.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Sat, 06 Jun 2009 16:30:07 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 03:02:16 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Fri, 05 Jun 2009 16:27:15 -0800, (Floyd L.
Davidson) wrote:
Or instead of your search on "voltage +quantization" (which gets
only 276,000 hits), try "voltage +analog" for 10 million hits.

Its only a list of searches relating to the problems of the
quantization of voltage.

Right, now do you understand what you just said?

The problems associated with the process of quatization of
voltage. Which means that voltage is analog, and there
are processes used to quantize it.

Duh!

You original assertion is there for a "Duh!"

If you read and understand the papers you will realise that they are
discussing the problems of the voltage being quantized.



Eric Stevens

Eric Stevens wrote:
On Sat, 06 Jun 2009 16:30:07 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 03:02:16 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Fri, 05 Jun 2009 16:27:15 -0800, (Floyd L.
Davidson) wrote:
Or instead of your search on "voltage +quantization" (which gets
only 276,000 hits), try "voltage +analog" for 10 million hits.

Its only a list of searches relating to the problems of the
quantization of voltage.

Right, now do you understand what you just said?

The problems associated with the process of quatization of
voltage. Which means that voltage is analog, and there
are processes used to quantize it.

Duh!

You original assertion is there for a "Duh!"

If you read and understand the papers you will realise that they are
discussing the problems of the voltage being quantized.

Cite?

"The quantized voltage steps are then shown to result from
topological invariance of the system."
http://prola.aps.org/abstract/PRB/v46/i1/p564_1

Oops, not a intrinsic characteristic of voltage, but rather a
specific environment.

"The quantization is the result of coupling between the flux
flow mode and the internal cavity resonances of the
junction."
http://cat.inist.fr/?aModele=afficheN&cpsidt=4069315

Oops, not a intrinsic characteristic of voltage, but rather a
specific environment.

There a couple hundred thousand others just like that...

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Sat, 06 Jun 2009 19:09:56 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 16:30:07 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 03:02:16 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Fri, 05 Jun 2009 16:27:15 -0800, (Floyd L.
Davidson) wrote:
Or instead of your search on "voltage +quantization" (which gets
only 276,000 hits), try "voltage +analog" for 10 million hits.

Its only a list of searches relating to the problems of the
quantization of voltage.

Right, now do you understand what you just said?

The problems associated with the process of quatization of
voltage. Which means that voltage is analog, and there
are processes used to quantize it.

Duh!

You original assertion is there for a "Duh!"

If you read and understand the papers you will realise that they are
discussing the problems of the voltage being quantized.

Cite?

"The quantized voltage steps are then shown to result from
topological invariance of the system."
http://prola.aps.org/abstract/PRB/v46/i1/p564_1

Oops, not a intrinsic characteristic of voltage, but rather a
specific environment.

"The quantization is the result of coupling between the flux
flow mode and the internal cavity resonances of the
junction."
http://cat.inist.fr/?aModele=afficheN&cpsidt=4069315

Oops, not a intrinsic characteristic of voltage, but rather a
specific environment.

There a couple hundred thousand others just like that...

http://www.iop.org/EJ/abstract/0305-4470/15/5/017
"Quantum electrodynamic theory of voltage carrying states..."



Eric Stevens

Eric Stevens wrote:

heavily edited for brevity

Dingbat - interpolation is an assential part of going from the Bayer
array to the RAW data file. Please don't continue to pretend
otherwise.

edited

Hello, Eric:

"Dingbat," eh? Why don't youss dummy up, ya meathead, ya! g


Cordially,
John Turco

On Sun, 07 Jun 2009 11:53:51 +1000, Bob Larter
wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 20:29:27 +1000, Bob Larter
wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 14:45:53 +1000, Bob Larter
wrote:

Well, Eric's correct to say that at a quantum level, you're dealing with
integer numbers of photons & electrons, but he's missing the important
point, which is that an image sensor doesn't have any way of 'counting'
anything, & that the output voltage is merely an approximation of the
input signal.
Which is then digitised to the necessary level of accuracy by
comparison with a ramp signal.
You're thinking of dual-slope conversion, as used in multimeters & the
like. Dual-slope is very, very slow. For this sort of application (ie;
fast) you either use a flash converter or a fast SAR converter.

Eg; something like this:
http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad9254/products/product.html
(Note that they aren't cheap.)

Its too long since I was involved with anything like this but as far
as I can see these all work by constructing a reference ramp signal
(not necessarily linear) comprised of individual reference voltages
with which to compare the input.

That's not the case.

You may use http://en.wikipedia.org/wiki/Analog-...ital_converter
to define the limits of my understanding. :-)

From that article:
---
* A direct conversion ADC or flash ADC has a bank of comparators,
each firing for their decoded voltage range. The comparator bank feeds a
logic circuit that generates a code for each voltage range. Direct
conversion is very fast, but usually has only 8 bits of resolution (255
comparators - since the number of comparators required is 2n - 1) or
fewer, as it needs a large, expensive circuit. ADCs of this type have a
large die size, a high input capacitance, and are prone to produce
glitches on the output (by outputting an out-of-sequence code). Scaling
to newer submicrometre technologies does not help as the device mismatch
is the dominant design limitation. They are often used for video,
wideband communications or other fast signals in optical storage.

* A successive-approximation ADC uses a comparator to reject ranges
of voltages, eventually settling on a final voltage range. Successive
approximation works by constantly comparing the input voltage to the
output of an internal digital to analog converter (DAC, fed by the
current value of the approximation) until the best approximation is
achieved. At each step in this process, a binary value of the
approximation is stored in a successive approximation register (SAR).
The SAR uses a reference voltage (which is the largest signal the ADC is
to convert) for comparisons. For example if the input voltage is 60 V
and the reference voltage is 100 V, in the 1st clock cycle, 60 V is
compared to 50 V (the reference, divided by two. This is the voltage at
the output of the internal DAC when the input is a '1' followed by
zeros), and the voltage from the comparator is positive (or '1')
(because 60 V is greater than 50 V). At this point the first binary
digit (MSB) is set to a '1'. In the 2nd clock cycle the input voltage is
compared to 75 V (being halfway between 100 and 50 V: This is the output
of the internal DAC when its input is '11' followed by zeros) because 60
V is less than 75 V, the comparator output is now negative (or '0'). The
second binary digit is therefore set to a '0'. In the 3rd clock cycle,
the input voltage is compared with 62.5 V (halfway between 50 V and 75
V: This is the output of the internal DAC when its input is '101'
followed by zeros). The output of the comparator is negative or '0'
(because 60 V is less than 62.5 V) so the third binary digit is set to a
0. The fourth clock cycle similarly results in the fourth digit being a
'1' (60 V is greater than 56.25 V, the DAC output for '1001' followed by
zeros). The result of this would be in the binary form 1001. This is
also called bit-weighting conversion, and is similar to a binary search.
The analogue value is rounded to the nearest binary value below, meaning
this converter type is mid-rise (see above). Because the approximations
are successive (not simultaneous), the conversion takes one clock-cycle
for each bit of resolution desired. The clock frequency must be equal to
the sampling frequency multiplied by the number of bits of resolution
desired. For example, to sample audio at 44.1 kHz with 32 bit
resolution, a clock frequency of over 1.4 MHz would be required. ADCs of
this type have good resolutions and quite wide ranges. They are more
complex than some other designs.
---

You're thinking of either a ramp-compare, dual-slope or delta-encoded
ADC, all of which are much too slow for a digital camera.

Yes, once you have reference voltages you don't need to re-establish
them every ti. But just out of curiousity, how are they established in
the first place?



Eric Stevens

On Sun, 07 Jun 2009 11:56:17 +1000, Bob Larter
wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 03:10:45 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On Sat, 06 Jun 2009 14:45:53 +1000, Bob Larter
wrote:

Well, Eric's correct to say that at a quantum level, you're dealing with
integer numbers of photons & electrons, but he's missing the important
point, which is that an image sensor doesn't have any way of 'counting'
anything, & that the output voltage is merely an approximation of the
input signal.
Which is then digitised to the necessary level of accuracy by
comparison with a ramp signal.
Comparison witha reamp signal???

You've been doing some research, and now the whole concept of
digital voltmeters is confusing you just as much as are digital
cameras!

Yeah. I did some research, way back in the mid 1960s. I did more with
the introduction of digital music (whenever that was). So I do have
some idea of what I am talking about.

All of the ramp-based converters are too slow to be any use for reading
an image sensor. It'd take *minutes* to read a single image.

I'm not suggesting that this is how it is done with image sensors. I
was just using this, along with my brick and spring-balance analogy to
explain to Floyd how a nominally analog voltage signal can be used to
digitize data.



Eric Stevens