From: ASAAR on
On Sat, 17 Mar 2007 16:00:50 -0400, John Smith wrote:

>> Here are some scenarios,
>> Indoor shooting of people talking with hand gestures, people walking
>> or pacing in the room, kids playing, women cooking in kitchen, or
>> groups of people in meeting rooms etc. Sometimes I don't have the
>> ability to use lights, I need to depend on flash and high brightness
>> setting. Currently, I am using a Sony Digital Camera, Cyber-shot, DSC-
>> H2. My budget is $1000 and at the most $1500.
>
> When you say "hand gestures" you mean they get angry if you use
> a flash or other additional light source?

I think that yip meant that if photos of those subjects are taken
in dim light without the use of a flash, the various movements, such
as hands moving about while gesturing will result in image blur.
Did you *really* think that?


> Sounds like you're going to be working in a confined area. If you don't need
> the long reach of a zoom, you might want to consider something like the
> Nikon D40, throw away the kit lens, and buy a 50mm 1.8 (about 100$give or
> take) Nice fast lens, and the camera is getting good reviews for higher ISO
> shootin'.

Set aside when not needed, maybe, but throw it away? Anyway, the
slightly larger, slightly more capable D50 is still available new
from B&H without kit lens for $108 less than the D40 with 18-55mm
kit lens. It's low light performance is virtually identical to the
D40's, so you could get a D50 with 50mm f/1.8 lens for less than the
cost of the D40 with the relatively inferior 18-55mm kit lens.
Every reviewer other than Ken Rockwell seems to think that Nikon's
18-70mm lens is a much more capable lens, even though it's more
expensive. Faster in both operating speed and lens aperture,
sharper, less distortion and it has a metal mount and includes a
lens hood vs. the plastic used by the 18-55mm lens which does not
include the hood.


> I'm going to order one myself tomorrow night.

Congratulations. I'll probably do the same, but substitute a D50
for the D40, since I don't know how much longer they'll be available
new, and I recently found out that my old Ai-S lenses are atypical
in that they don't require a D200 to be fully functional, but they'd
lose both AF and metering capability on a D40.

From: John Sheehy on
Doug McDonald <mcdonald(a)SnPoAM_scs.uiuc.edu> wrote in
news:eth6t0$pcg$1(a)news.ks.uiuc.edu:

> I should add that in the limit of really small pixels, I suppose that
> a designer could get the read noise well below 1 electron. When that
> happens, you really DO reach the limit where smaller pixels are better
> (except for fill factor arguments and the associated factor of
> microlenses.) It IS possible to get semiconductor read noise below one
> electron, it just hard to do very fast. With read noise well below one
> electron, and enough analog gain, amplifier noise at low signals
> (streaks) can be processed way.

Popular belief varies greatly from forum to forum. There are a good number
of people who are on top of the technological issues in the Open Talk and
News Discussion forums on DPReview, even people who actually design digital
cameras, and there is more of a belief there that the future lies in true
digital imaging; gigapixel digital sensors, measuring as little as one
photon per pixel, with one bit of depth. IIRC, there are already
prototypes of some of this technology.

No color aliasing. No downsampling artifacts. No need for AA filters, or
teleconverters (except for the optical viewfinders). Just highly detailed
photon capture.


--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS(a)no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
From: acl on
On Mar 18, 12:47 am, John Sheehy <J...(a)no.komm> wrote:
> Doug McDonald <mcdonald(a)SnPoAM_scs.uiuc.edu> wrote innews:eth6t0$pcg$1(a)news.ks.uiuc.edu:
>
> > I should add that in the limit of really small pixels, I suppose that
> > a designer could get the read noise well below 1 electron. When that
> > happens, you really DO reach the limit where smaller pixels are better
> > (except for fill factor arguments and the associated factor of
> > microlenses.) It IS possible to get semiconductor read noise below one
> > electron, it just hard to do very fast. With read noise well below one
> > electron, and enough analog gain, amplifier noise at low signals
> > (streaks) can be processed way.
>
> Popular belief varies greatly from forum to forum. There are a good number
> of people who are on top of the technological issues in the Open Talk and
> News Discussion forums on DPReview, even people who actually design digital
> cameras, and there is more of a belief there that the future lies in true
> digital imaging; gigapixel digital sensors, measuring as little as one
> photon per pixel, with one bit of depth. IIRC, there are already
> prototypes of some of this technology.
>
> No color aliasing. No downsampling artifacts. No need for AA filters, or
> teleconverters (except for the optical viewfinders). Just highly detailed
> photon capture.
>

Exactly, but you cannot see this if you're stuck at thinking in terms
of today's electronics (as most people here are). Knowledge inertia.

From: Doug McDonald on
John Sheehy wrote:
>
> What are you comparing it against? Let's say you have 9 tiny pixels with
> a signal of 5 electrons, and a read noise of 2.7 electrons. 9 of those,
> binned together, have a signal of 45 electrons, and a read noise of 8.1
> electrons. With hardware binning like Dalsa uses, that might mean 2.7
> electrons (or a tad more) even for the binned superpixel.


Hardware binning, that is, adding the charge before the amplifiers,
does indeed work fine, except you lose the resolution!


As I said in another post, all else (i.e. fill factor) being
equal, smaller pixels do result in a smaller read noise due
to smaller capacitance. The downside of course is lower
dynamic range.

Doug McDonald
From: Roger N. Clark (change username to rnclark) on
John Sheehy wrote:
> Doug McDonald <mcdonald(a)SnPoAM_scs.uiuc.edu> wrote in
> news:eth4fs$o8k$1(a)news.ks.uiuc.edu:
>
>> John Sheehy wrote:
>
>>> Of course not, but many people believe so for capturing photons
>>> instead of raindrops!
>
>> That last sentence is WRONG. That said, it is wrong only because
>> of read noise, which is of the order of 3 to 5 electrons.
>
> This was a thought experiment, to isolate the shot noise issue. People
> are always saying that smaller pixels means more shot noise. That is
> what this was about. Read noise is another subject, but the fact is,
> read noise in the real world decreases with smaller pixels, either in
> binning, downsampling, or considering noise power as a function of
> magnification.
>
> Read noise is 2.7 electrons in my FZ50 at ISO 100. 9 of those pixels
> binned together equal a typical DSLR pixel both in coverage area, and
> maximum photon count. 2.7 * 9^0.5 = 8.1 electrons of read noise for the
> "superpixel". That's about 1/3 of the ISO 100 read noise on my 20D.

Your number for the 20D is incorrect. What you refer to as read noise
is not true sensor read noise, but the limitation of a 12-bit A/D converter.
The 20D has a full signal well depth of 51,000 electrons.
So: 51000/4095 = 12.5 electrons per A/D bit. Add +/- 1 bit noise
on each A/D reading, and noise should be about 1.4 bits, or
1.4 * 12.5 = 17.5 electrons not including actual sensor read
noise. DSLRs are so good at low ISOs, they are limited at the
low end by A/D converter electronics, not sensor read noise.

Small pixel P&S cameras get so few photons, that the entire range
is adequately characterized by 12-bit converters.

Roger
>
>> If the
>> actual signal is bigger than say 100 photoelectrons the read
>> noise becomes negligible. Nevertheless, at the very lowest signal
>> levels, your argument is wrong in the real quantized world.
>
> What are you comparing it against? Let's say you have 9 tiny pixels with
> a signal of 5 electrons, and a read noise of 2.7 electrons. 9 of those,
> binned together, have a signal of 45 electrons, and a read noise of 8.1
> electrons. With hardware binning like Dalsa uses, that might mean 2.7
> electrons (or a tad more) even for the binned superpixel. A typical DSLR
> at ISO 100 will have a read noise of 18 to 30 electrons.
>
> Large pixels are not doing well in current technology, in terms of read
> noise at low ISOs!

Again, not doing well with 12-bit A/Ds. That is why canon has
now announced a camera with 14-bit A/Ds. We'll see more of that
in the future,
>
> The real world does not match your boogey-man stories of read noise
> problems with small pixels.

The real world marches to a complete description of physics,
not a narrow view to push an agenda.

Roger