From: ejmartin on 23 Jul 2008 16:23
On Jul 23, 3:09 pm, Bob Newman <bob.csx...(a)gmail.com> wrote:
> On 23 Jul, 19:14, ejmartin <ejm_60...(a)yahoo.com> wrote:
> > On Jul 23, 12:42 pm, Bob Newman <bob.csx...(a)gmail.com> wrote:
> > > There's a wealth of
> > > interesting stuff in Eric's workshop papers, ...
> > Indeed. Here's one that proposes some theory for 1/f noise, extending
> > your model:
> > Look at section 4.
> Yup, and look at figure 5. There is predictable behaviour there that
> could be used to identify the flicker noise and process it out - real
> 'noise reduction'.
> One of the other papers is about 'backside illuminated sensors' -
> presumably they need to be made of Gallium Arsenide :D
Why do you say it's predictable? In terms of the output yes, but I
thought the point was that you couldn't predict when the interface
will trip into the "excited" state, which is why there is a 1/f random
From: Bob Newman on 23 Jul 2008 17:07
On 23 Jul, 21:23, ejmartin <ejm_60...(a)yahoo.com> wrote:
> On Jul 23, 3:09 pm, Bob Newman <bob.csx...(a)gmail.com> wrote:
> > On 23 Jul, 19:14, ejmartin <ejm_60...(a)yahoo.com> wrote:
> > > On Jul 23, 12:42 pm, Bob Newman <bob.csx...(a)gmail.com> wrote:
> > > > There's a wealth of
> > > > interesting stuff in Eric's workshop papers, ...
> > > Indeed. Here's one that proposes some theory for 1/f noise, extending
> > > your model:
> > >http://imagesensors.org/Past%20Workshops/2005%20Workshop/2005%20Paper...
> > > Look at section 4.
> > Yup, and look at figure 5. There is predictable behaviour there that
> > could be used to identify the flicker noise and process it out - real
> > 'noise reduction'.
> > One of the other papers is about 'backside illuminated sensors' -
> > presumably they need to be made of Gallium Arsenide :D
> Why do you say it's predictable? In terms of the output yes, but I
> thought the point was that you couldn't predict when the interface
> will trip into the "excited" state, which is why there is a 1/f random
> noise spectrum.
You can't detect 'when', but you can detect 'if'. Multiple sample,
exclude the high samples, noise gone. This might take longer, but it
could be a user choice - fast/noisy, slow/quiet.
From: Bob Newman on 23 Jul 2008 17:09
On 23 Jul, 21:01, John Sheehy <J...(a)no.komm> wrote:
> rfisc...(a)sonic.net (Ray Fischer) wrote in news:4886dd50$0$17165
> > Don't try to feed me bullshit in order to justify your weak argument.
> I haven't even told you what my weak argument is yet.
> <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
> John P Sheehy <J...(a)no.komm>
> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
From: John Turco on 25 Jul 2008 00:28
"Roger N. Clark (change username to rnclark)" wrote:
> John Sheehy wrote:
> > Then again, I'm the guy who got 100% on all his math and most of his
> > science tests, without studying, so maybe I'm expecting too much.
> So what happened? I showed you some of your math and conceptual
> errors but you failed to recognize them.
Look at the bright side: This current controversy has hastened your
return to <news:rec.photo.digital>, at least.
Welcome back, doc! <g>
John Turco <jtur(a)concentric.net>
From: Roger N. Clark (change username to rnclark) on 26 Jul 2008 18:00
Bob Newman wrote:
> I really do agree it's impressive, and a very useful body of work.
> However, I think you need to understand the limitations of such data,
> and how far you can stretch it in terms of analysis of trends from it.
> For instance, I have had your site quoted at me as irrefutable
> evidence that the 5D has a higher FWC than the D3. Certainly, most of
> your graphs show the 5D outperforming the D3. Does it? I don't know,
> but some of your figures are taken from Peter Facey, yet in his direct
> comparison, the D3 has a higher FWC. Because of the constraints, these
> figures are not exact, and it's fruitless to talk about
> interpretations which are in the noise, unless you can average a very
> large numebr of such datapoints to reduce the noise ;-)
I was out of town for a while (actually in Paris wthh little time
for internet discussion).
While I agree one must be careful with non-sensor manufacturer data,
we also have a lot of sensor manufacturer data and both the EOM
and amateur derived data are showing the same trends. In the case of the
D3, yes, Peter failed to make measurements at lower ISO to determine
the real saturation value of the sensor, so his quoted full well
number is low. But other factors, such as the unity gain ISO are higher
than any other consumer camera, showing the D3's superb low light
capability that falls about where expected for its largest DSLR pixels
would indicate. Then if one looks at the full well value noting it's
at ISO 200 (I think I'm remebering all this correctly), the dynamic range
is also higher than other cameras at ISO 200. So while the Full well
is probably too low, the camera's large pixels still have stunning
performance. In practice, the newer generation electronics of the D3
probably have less fixed pattern noise than the 5D, so it is somewhat
blind spec viewing to try and make a conclusion about which camera performs
better. In general, newer cameras generally do better, especially
when pixel count and sensor sizes are about the same.
>>> One of
>>> your major criticisms of John's stuff is based on an assumption that
>>> 'read noise', referred to photo-electrons, remains approximately
>> I never said read noise is constant, at least between sensors.
>> What I said was there was NO correlation of read noise with pixel size.
>> Read noise is independent of ISO because ISO is a post sensor read gain.
>> Read noise varies a lot between different sensors because of different
>> methods for reading the signal and suppressing noise.
> I believe there is a weak corelation in theory (in that input referred
> read noise is clearly scaled by the cell capacitance, which is weakly
> related to cell area). The best you can say is that there is no
> evidence in your data to support that, not that there is no
There is also no evidence in the sensor manufacturer data either.
In general, the conversation you've been having with Emil about
components in equations including T and C (temp and capacitance),
current read noise shows little to no temperature dependence.
The capacitance may be showing but one can't tell between the many
sensors because other parameters that are traded off.
I have heard of large pixel laboratory/telescope CCDs having sub electron
read noise with a combination of low temperature sensors and electronics
and slow readout times (e.g ~30 seconds / megapixel).
So in theory we might someday see lower read noise sensors
in consumer cameras. After all, 4 electron read noise was
amazing not that long ago in the lab. But we have yet to
see any consumer room temperature camera with less than
3 electron read noise, regardless of pixel size.