D3 sensor efficiency

ejmartin

Veteran Member
Messages
6,236
Reaction score
4
Location
Chicago, IL, US
As a companion to the dynamic range measurement reported here:
http://forums.dpreview.com/forums/read.asp?forum=1021&message=25627719

I have now also measured the (full well) capacity of the pixels of the Nikon D3. I found that at the base ISO of 200, the full well capacity is 53,400 electrons, a new high among DSLR's. The previous record holder was the Canon 1Dmk3, whose well capacity at ISO 200 is about 39,500.

To put this in perspective, if we scale up the 7.2 micron photosites of the 1Dmk3 to the size 8.46 microns of the D3 photosites, the scaled up photosites would have 54,600 electrons full well -- the same within experimental error. It seems then that the D3 and the 1D mark 3 have about the same level of sensor technology, just different choices for sensor size and pixel pitch. The read noises are comparable too: I found 4.9 14-bit raw levels of read noise at ISO 200, 14.3 at ISO 1600, and 23.3 at ISO 3200 for the D3; and for the 1Dmk3, 4.9 @ISO200, 12.1@ISO1600, and 23.8@ISO3200.

So it looks as though the D3 will indeed be the high ISO champion, by about .2 stop per pixel in midtones and highlights (and marginally even better as a percentage of image area due to having 20% more pixels, pushing the noise to finer spatial scales where it is less noticeable); the above figures tell us the relative photon noise levels when viewed at 100% (at the pixel level) are essentially the same as the ratio of pixel pitches. In shadows, the read noise dominates and the performances of the two cameras are roughly the same.

Note that my analysis was carried out on the raw files themselves, prior to raw conversion that adds additional uncontrolled effects to the image. The pixel capacity is a property of the sensor itself. A lot of high ISO samples from the D3 are jpegs exhibiting strong noise reduction (especially chroma noise); the direct analysis of the raw files renders that issue moot.
--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
In your previous post you mentioned that the DR of D3 is around 11.5 EV. With the same method you did your test, as a comparison, do you have any D200 or Fuji S5 Dr data by the same way you tested D3?
 
In your previous post you mentioned that the DR of D3 is around 11.5
EV. With the same method you did your test, as a comparison, do you
have any D200 or Fuji S5 Dr data by the same way you tested D3?
I have not carried out nor seen elsewhere a direct analysis of the Fuji raw data with regard to sensor characteristics. For the Nikon D200 the sorts of results I have been reporting can be found at Roger Clark's website
http://www.clarkvision.com/imagedetail/evaluation-nikon-d200/index.html

Clark reports an 11.7 stop DR for the D200, but if I recall correctly he doesn't take into account the fact that Nikon clips the blackpoint, and if he hasn't corrected for that his methodology would lead him to under-report the read noise of the camera by a factor 1.66, or about .7 stop. I suspect the true figure for the D200 DR is about 11 stops. His figures for full well capacity should be fairly accurate.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
Thanks. That's very disappointing. :( That means D3 will have the same DR as D200 which was reported by Phil just has 8 EV usable DR.

I really hope D3 with its much bigger photo sites will increase its Dr significantly.
 
Thanks. That's very disappointing. :( That means D3 will have the
same DR as D200 which was reported by Phil just has 8 EV usable DR.
I really hope D3 with its much bigger photo sites will increase its
Dr significantly.
Two points to note here:

1. The engineering definition that I, Clark and others are using is a rather liberal definition of DR; it sets the noise floor as the noise at zero signal. Most people would stop well before then. The part of the range where the signal is "high quality" will be larger on the D3 because of those large photosites; that is what the well capacity measurement tells us.

2. The DR by any definition will be much better on the D3 at high ISO than it is on the D200, due to the advantages of CMOS technology over the CCD used in the D200. Even according to the engineering definition, it's over two stops better at ISO 1600.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
I have now also measured the (full well) capacity of the pixels of
the Nikon D3. I found that at the base ISO of 200, the full well
capacity is 53,400 electrons, a new high among DSLR's. The previous
record holder was the Canon 1Dmk3, whose well capacity at ISO 200 is
about 39,500.
Full well capacity has nothing to do with ISO setting. Do you really mean to say that you are measuring the electron count which corresponds to the converter full-scale code at ISO 200?
To put this in perspective, if we scale up the 7.2 micron photosites
of the 1Dmk3 to the size 8.46 microns of the D3 photosites, the
scaled up photosites would have 54,600 electrons full well -- the
same within experimental error. It seems then that the D3 and the 1D
mark 3 have about the same level of sensor technology, just different
choices for sensor size and pixel pitch.
In other words, quantum efficiency is the same. I'm rather disappointed that Nikon's elaborate microlens design hasn't improved on the Mk III in this respect.
Note that my analysis was carried out on the raw files themselves,
prior to raw conversion that adds additional uncontrolled effects to
the image.
What software or method are you using to analyze the raw data? I'm still waiting patiently for Mike Unsold to issue ImagesPlus 3.0, which will have Mk III compatibility (and hopefully D3 as well).
Thank you for posting the data.
 
I have now also measured the (full well) capacity of the pixels of
the Nikon D3. I found that at the base ISO of 200, the full well
capacity is 53,400 electrons, a new high among DSLR's. The previous
record holder was the Canon 1Dmk3, whose well capacity at ISO 200 is
about 39,500.
Full well capacity has nothing to do with ISO setting. Do you really
mean to say that you are measuring the electron count which
corresponds to the converter full-scale code at ISO 200?
Yes, perhaps a misapplication of terminology. I meant the electron count where the signal is clipped at that ISO. The well may or may not be saturated, even though this is the base ISO. And it has nothing to do with any converter.
To put this in perspective, if we scale up the 7.2 micron photosites
of the 1Dmk3 to the size 8.46 microns of the D3 photosites, the
scaled up photosites would have 54,600 electrons full well -- the
same within experimental error. It seems then that the D3 and the 1D
mark 3 have about the same level of sensor technology, just different
choices for sensor size and pixel pitch.
In other words, quantum efficiency is the same. I'm rather
disappointed that Nikon's elaborate microlens design hasn't improved
on the Mk III in this respect.
Note that my analysis was carried out on the raw files themselves,
prior to raw conversion that adds additional uncontrolled effects to
the image.
What software or method are you using to analyze the raw data? I'm
still waiting patiently for Mike Unsold to issue ImagesPlus 3.0,
which will have Mk III compatibility (and hopefully D3 as well).
Thank you for posting the data.
I used dcraw with option -D to read out the raw data (the latest build supports the D3 and D300), and converted to fits format with the netpbm package; then loaded the result into IRIS, split the CFA into color channels, selecting small uniform patches to sample mean and st dev. I actually used an ISO 1600 file for the analysis for arcane reasons, then scaled up the results to ISO 200. Subtracting off (in quadrature) a previous measurement of the read noise gave the photon shot noise in raw levels. The ratio of the mean raw level to the shot noise squared yields the conversion between electrons and raw units. After rescaling to ISO 200 I got 13.0 electrons/12-bit ADU, + - 0.5. Multiplying by 4095 gives the quoted number of electrons at raw saturation.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
I used dcraw with option -D to read out the raw data (the latest
build supports the D3 and D300), and converted to fits format with
the netpbm package; then loaded the result into IRIS, split the CFA
into color channels, selecting small uniform patches to sample mean
and st dev. I actually used an ISO 1600 file for the analysis for
arcane reasons, then scaled up the results to ISO 200. Subtracting
off (in quadrature) a previous measurement of the read noise gave the
photon shot noise in raw levels. The ratio of the mean raw level to
the shot noise squared yields the conversion between electrons and
raw units. After rescaling to ISO 200 I got 13.0 electrons/12-bit
ADU, + - 0.5. Multiplying by 4095 gives the quoted number of
electrons at raw saturation.


--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
Hello Emil,

Very intereting work. As I'm sure you know, pixel-to-pixel nonuniformities can also contribute to your standard deviations. Since I don't know much about the degree of pixel-to-pixel nonuniformity of these sensors, do you have a feel for the size of these nonuniformities, and whether it is so small as to not be a worry?

Thanks,

Chris
 
Thanks. That's very disappointing. :( That means D3 will have the same DR as D200 which was reported by Phil just has 8 EV usable DR.

I really hope D3 with its much bigger photo sites will increase its Dr significantly.
That's exactly what you can find in the full D3 & D300 review in Chasseur d'Images, in their conclusion they write: "@ iso 100 there is a big loss on DR. Overall DR stays classique... "

About D3 that is one of the two less flathering conclusions next to "D3 AF points coverage which is quiet narrow..."

Out of that they quote D3 only in superlatives...
--
Kindest regards,
Stany
I prefer one really good picture in a day over 10 bad ones in a second...

http://www.fotografie.fr/
 
Hello Emil,

Very intereting work. As I'm sure you know, pixel-to-pixel
nonuniformities can also contribute to your standard deviations.
Since I don't know much about the degree of pixel-to-pixel
nonuniformity of these sensors, do you have a feel for the size of
these nonuniformities, and whether it is so small as to not be a
worry?
The only way to know for sure is to have two identical images so as to be able to subtract them, response nonuniformity then cancels in the difference image leaving only the read and shot noise. I have measured this effect on the Canon 1Dmk3 and 20D. There the response nonuniformity leads to fluctuations in the raw level that are roughly equal to photon shot noise, in the highlights at ISO 100.

Now, the Nikon D3 measurements I did were at ISO 1600, precisely in order to mitigate this effect (I then converted the answer to ISO 200 by multiplying by the ratio of the gain factors).

Let us assume that the response nonuniformity of the Nikon D3 sensor is at about the same level as on the Canon sensors. Then in going from ISO 100 to 1600, the response nonuniformity goes down by a factor of 16 since it is proportional to the gain, while the photon noise goes down by a factor of 4 since it is proportional to the sqrt of signal. So at ISO 1600, the response nonuniformity should be about 4 times smaller in the highlights (where I did the measurements) than the photon shot noise. When adding the noises in quadrature, the response nonuniformity will produce a roughly 3% correction, which is well within the uncertainty of the measurements I was doing. But you are right, my value might be a teensy bit low due to this effect.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
To put this in perspective, if we scale up the 7.2 micron photosites
of the 1Dmk3 to the size 8.46 microns of the D3 photosites, the
scaled up photosites would have 54,600 electrons full well -- the
same within experimental error. It seems then that the D3 and the 1D
mark 3 have about the same level of sensor technology, just different
choices for sensor size and pixel pitch.
In other words, quantum efficiency is the same. I'm rather
disappointed that Nikon's elaborate microlens design hasn't improved
on the Mk III in this respect.
Hm, how big is the difference between 5D and Mk III in this respect?
Here is a comparison of QE to the 5D:
http://forums.dpreview.com/forums/read.asp?forum=1018&message=25654095
 
Full well capacity has nothing to do with ISO setting. Do you really
mean to say that you are measuring the electron count which
corresponds to the converter full-scale code at ISO 200?
Yes, perhaps a misapplication of terminology. I meant the electron
count where the signal is clipped at that ISO. The well may or may
not be saturated, even though this is the base ISO. And it has
nothing to do with any converter.
Emil,

Thanks for posting the data and excellent analysis. However, to call the D3 the new champion in full well is a bit misleading when Roger Clark reports the full well of the Canon 1D MII at 79,900 electrons, compared to the 53,400 that you measured. Roger has no data for the 1D MIII as yet.

Of course, the Nikon full well is at ISO 200 whereas the Canon is at ISO 50 (actually it would occur at ISO 75, according to Roger, but that ISO is not available). What does this mean? My take is that, since the Canon has a higher full well capacity, shot noise would be less. Since the Nikon achieves full well at ISO 200, its sensor must be more sensitive to light than the Canon. In an analogy with film, it is as though you are using ISO 200 film in the Nikon, but ISO 50 (or 75) film in the Canon.

BTW, how did you obtain the images for your test?

Bill
 
...of full-well capacity.

I expect 1D3 to offer such performance at ISO100, though, since ISO50 will most likely be pure meta-data, as it currently is on 5D.

What is the D3's real maximum full-well capacity? Sorry if I missed anything, here...

Roger Clark has not published his results, yet, which I kind of look forward to it.

PIX

--

TIP: If you do not like this post, simply press the 'COMPLAINT' button. Mommy/Daddy are just one click away.
 
Of course, the Nikon full well is at ISO 200 whereas the Canon is at
ISO 50 (actually it would occur at ISO 75, according to Roger, but
that ISO is not available).
...That iso WAS and IS available. Simply set Personal/Custom function to expand ISO to "L" and "H", and dial a permanent -0.3EV E.C. and voila! Enjoy ULTRA clean, noise-free shadows on the 1D2/N, as long as Lightroom/ACR is used.

Enjoy!

--

TIP: If you do not like this post, simply press the 'COMPLAINT' button. Mommy/Daddy are just one click away.
 
Emil,

Thanks for posting the data and excellent analysis. However, to call
the D3 the new champion in full well is a bit misleading when Roger
Clark reports the full well of the Canon 1D MII at 79,900 electrons,
compared to the 53,400 that you measured. Roger has no data for the
1D MIII as yet.

Of course, the Nikon full well is at ISO 200 whereas the Canon is at
ISO 50 (actually it would occur at ISO 75, according to Roger, but
that ISO is not available). What does this mean? My take is that,
since the Canon has a higher full well capacity, shot noise would be
less. Since the Nikon achieves full well at ISO 200, its sensor must
be more sensitive to light than the Canon. In an analogy with film,
it is as though you are using ISO 200 film in the Nikon, but ISO 50
(or 75) film in the Canon.
I probably should not have used the term "full well capacity", rather what I quoted is more properly called the number of photoelectrons at raw saturation. If you like, it is easily converted to the number of photoelectrons/raw level (what Clark in a poor choice of terminology calls the "gain"). It is this figure that should be used to compare cameras on a level playing field -- if you shoot them side-by-side at the same Tv,Av, and ISO, the one collecting the most photons per raw level will have the least photon noise per pixel.
BTW, how did you obtain the images for your test?
I used the ones made available here:
http://aaronlinsdau.com/gear/articles/d3.html

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
What is the D3's real maximum full-well capacity? Sorry if I missed
anything, here...
As I've mentioned above, I was imprecise in my choice of terminology. What I really measured was the collection efficiency, photoelectrons per raw level, at ISO 1600, then scaled the results to ISO 200 at raw saturation (raw level 4095). Since sensors are linear up to very near saturation, and the change in ISO just scales the number of photoelectrons by a factor of eight, I think this is perfectly reasonable. Since the sensor wells were not full for the images I was using, this is not the full well capacity. For that one would have to find an ISO at which the sensor saturates before raw level 4095 is reached, as it is on Canons at their lowest ISO's.
Roger Clark has not published his results, yet, which I kind of look
forward to it.
Indeed. I hope he corrects for the clipping of blacks in Nikon raw when he measures read noise.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
To put this in perspective, if we scale up the 7.2 micron photosites
of the 1Dmk3 to the size 8.46 microns of the D3 photosites, the
scaled up photosites would have 54,600 electrons full well -- the
same within experimental error. It seems then that the D3 and the 1D
mark 3 have about the same level of sensor technology, just different
choices for sensor size and pixel pitch.
In other words, quantum efficiency is the same. I'm rather
disappointed that Nikon's elaborate microlens design hasn't improved
on the Mk III in this respect.
Hm, how big is the difference between 5D and Mk III in this respect?
Here is a comparison of QE to the 5D:
http://forums.dpreview.com/forums/read.asp?forum=1018&message=25654095
From Christian Buil's measurement of collection efficiency of the 5D, 4.08 electrons/12-bit raw level (ADU) at ISO 400, you would find 32,400 electrons at raw saturation at ISO 200, compared to the 39,500 of the 1D3 and 54,000 of the D3.

Or, in terms of electrons/12-bit ADU at ISO 200, the 5D comes in at 8.2, the 1D3 at 10.2, and the D3 at 13.1.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
I probably should not have used the term "full well capacity", rather
what I quoted is more properly called the number of photoelectrons at
raw saturation. If you like, it is easily converted to the number of
photoelectrons/raw level (what Clark in a poor choice of terminology
calls the "gain"). It is this figure that should be used to compare
cameras on a level playing field -- if you shoot them side-by-side at
the same Tv,Av, and ISO, the one collecting the most photons per raw
level will have the least photon noise per pixel.
Emil,

I'm not a electronics engineer, but according to the definition of gain posted below, Roger is using the term correctly. As indicated in the first link below.

"Because gain refers to the amplification of a system and the gain reported in CCD imaging is actually inverse amplification, the meaning of gain is not entirely intuitive."

http://www.photomet.com/library/library_encyclopedia/library_enc_gain.php

To confuse the situation further, Christian Buil uses the term "inverse gain". He reports further that Nikon does process the raw data before writing them to the memory card, and that they are not true raw files. This apparently applies only to exposures greater than one second.

http://www.astrosurf.com/buil/nikon_test/test.htm
BTW, how did you obtain the images for your test?
I used the ones made available here:
http://aaronlinsdau.com/gear/articles/d3.html
That means that you do not have a true bias (zero integration dark image) frame and that some of the variance in the dark region of the image could be due to nonuniform illumination and nonuniform reflectance in the dark areas rather than to read noise per se. The same reservations apply to the highlight data.

In addition, the camera has multiple readout channels, and if these are not properly balanced, fixed pattern noise may occur. These artifacts can be eliminated by subtracting two frames as recommended by Roger and the Photomet article.

Your data are most interesting and an example of what can be done with limited data, but shouldn't they be considered preliminary?

Bill
 
The reason I don't like the term "gain" is that nothing is being amplified. The thing being called "gain" is simply a conversion factor between two sets of units -- photoelectrons on the one hand, and raw levels on the other. Gain has no units; it is a pure number representing the ratio of output to input of the same quantity. If you converted dollars to euros, would you call it a gain? (Well some people might, but for a different reason ;)
--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
In other words, quantum efficiency is the same. I'm rather
disappointed that Nikon's elaborate microlens design hasn't improved
on the Mk III in this respect.
The Canon 1D Mark III also features new and improved microlenses which cover a larger area relative to the actual sensor. I think Nikon was perhaps just a bit louder in touting this improvement.
 

Keyboard shortcuts

Back
Top