From: Steve on

3On Sat, 19 Jul 2008 00:37:19 GMT, John Sheehy <JPS(a)no.komm> wrote:

>Steve <steve(a)> wrote in
>> On Thu, 17 Jul 2008 22:15:06 GMT, John Sheehy <JPS(a)no.komm> wrote:
>>>That makes no sense at all. I am not comparing cameras; I am comparing
>>>the effects of pixel density. I am fighting the myth that pixel noise
>> Actually, you're not doing that at all. What you are doing is
>> comparing the effects of resolution at the focal plane. No one can
>> argue that higher pixel density gives higher resolution at the focal
>> plane. And that's the only thing your test proves ... the obvious.
>> Only you can argue that this somehow translates to higher pixel
>> density gives better noise and DR performance in any real world image.
>> It doesn't, and the rest of the world knows that to be true no matter
>> how much you profess otherwise.
>I don't know what to say to you; you are being totally illogical. Can
>you find *any* way in which the 400D crop is less noisy than the FZ50

Yes. Give each sensor the same image, same ISO, same exposure, same
everything. Your test does not do that. You are making the 400D
capture an image that's almost 300% the size of the FZ50 and then
pixel peeping. That's not a fair test at all.

>I don't know what it is, but I can not for the life of me figure out how
>people can hold such unrealistic models in their heads. 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.
>My FZ50 crop shows what the resolution and noise would look like with the
>same exposure, same scene, etc, etc, with FZ50 pixels filling the same

Your test doesn't do that at all. Both cameras are not capturing the
same scene. You're giving the 400D a 289% larger scene to capture.

From: Roger N. Clark (change username to rnclark) on
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.
From: John Sheehy on
Steve <steve(a)> wrote in

> You said you're trying to measure the noise and DR of the sensor as
> pixel density changes.

This is not a measurement, per se. It is a real-image demonstration. I
think measurement, as it is usually done, is a bit flawed. SNR of pixel
statistics do no equal SNR of an image, and even if you take viewed pixel
size into account, which, when factored with pixel noise, gives a good
representation of visible noise, any image that is upsampled from the
original capture resolution needs to use a scaling factor based on the
*original* pixel's dispalyed size, not the individual pixel of the
upsized image. Statistical noise measurement has a serious hole in it,
where symmetry about the 1:1 scaling factor of pixels does not exist;
standard deviation of noise drops at the new pixel level when you
downsample, but it does not increase in an upsample, statistically, even
though it does increase visually, because standard deviations are totally
blind to the details of noise frequency.

> But the only thing you're measuring above is
> resolution of a given area of the focal plane.

That is all I claim to be measuring. Why do you think I am or should be
measuring something else. FOR THE SEEMINGLY MILLIONTH TIME: I AM NOT
"PIXEL DENSITY". Comparing a 12MP 1/2.5" sensor's image to that of a
12MP FF with the same field of view is *NOT* a comparison of pixel
density. It is a comparison of full images from different sensor sizes,
with the same number of pixels, which happen also to have different

> I don't think anyone
> is going to argue that higher pixel density gives better resolution at
> the focal plane. But that is absolutely meaningless if the size of
> the sensor is different.

Pixel density is discussed concerning sensors of the same size. There
the same area from cameras with vastly different pixel densities, AND
sensor size, to extrapolate what a large sensor with high pixel density
might do, compared to the low pixel density that larger sensors now have.

> Almost nobody except you and some people
> with special applications that may require a small sensor size cares
> about resolution at the focal plane.

So why the hell are you and all the rest of the peanut gallery replying
to my posts, if this doesn't interest you? Do you burst into churches on
Sunday morning to anounce that their religion doesn't interest you? Do
you go to sporting events to protest people's interest in sports? So
why, then, do you fell a need to come here in this thread and tell us
that the subject matter is irrelevant to you?

> The measure of resolution the
> rest of us care about is the resolution of the image captured by the
> entire sensor.

Who said I don't care about that? What I am interested in, is what
different pixel densities or pitches do in sensors of a given size. A
bigger sensor is better for noise, unless the MFR messed up with low QE
or excessive read noise. That is undisputed. My point is that lower
pixel densities don't do much of anything good for IQ, in a given sensor
size. The only benefit, IQ-wise, is that the big-pixel CMOS DSLRs like
the D3 and the 1D3 have lower image-level read noise at ISOs around 1600
and above, and only by a small amount, less than a stop, while still
having far less resolution than 8.35x as many 2 micron pixels would. And
who knows how much lower they could get the read noise of the small
pixels, if they weren't budgeting for $200 pocket cameras, or $500
cameras with sharp zoom lenses? I've heard from more than one source
that read noises can be had as low as 1 electron with 1-micron pixels, in
the lab. So, let's say that each 1-micron pixel collected up to 1000
electron charges; that's a ratio of 1000:1 for max signal to read noise.
4 of these pixels would be 4000:2 or 2000:1, 9 would be 9000:3 or 3000:1
(about the same as the 1-series Canons and the D3 at the virtual pixel
level, and you're still only binning to 3 microns). At 8 microns, you
have 64000:8, or 8000:1, a virtual pixel-level DR far beyond *any* DSLR
with ~8 micron pixel pitches.

> Your test of DR and noise vs. pixel density is not valid because you
> did not take the variable of resolution out of the equation by keeping
> it constant for the images captured.

Nonsense. It is valid for what *I* am testing. I don't care what you
think I should be testing. I am not comparing sensors of different
sizes, with similar MP counts. That is old hat; it is accepted and
doesn't need to be proven that bigger sensors usually collect more
photons and give lower image shot noise!

> I.e., if you have two 10MP
> sensors of different sizes, the only real world meaningful way to
> measure noise and DR vs. pixel density is to allow both 10MP sensors
> to capture a similar scene across the entire sensor and then compare
> the results at 100%.

Nonsense. That is a test of SENSOR SIZE, not PIXEL DENSITY.

> If you don't do it that way, then you are adding
> another variable (different magnifications even though the sensors
> have the same total number of pixels) to the equation.

The number of pixels that the sensors have, and the size of the sensors,
are TOTALLY IRRELEVANT to the issue of PIXEL DENSITY. Pixel Density only
concerns the number of pixels per unit of area.

> When you do
> that, you are no longer measuring the noise and DR of a sensor when
> only the pixel density changes.

> I'm pretty sure you understand this and are just trying to troll for
> an argument.

I've given far more than just a hint of what I am demonstrating here, yet
almost no one who has responded seems to understand. My thoughts are
going way over your head, apparently.


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John P Sheehy <JPS(a)no.komm>
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From: Ray Fischer on
John Sheehy <JPS(a)no.komm> wrote:
>ASAAR <caught(a)> wrote in
>> On Thu, 17 Jul 2008 22:15:06 GMT, John Sheehy wrote:
>>> That makes no sense at all. I am not comparing cameras;
>> Only because sense can't penetrate your thick skull. People don't
>> buy sensors.
>I don't care what people do. I care about what gives or potentially
>gives the best imaging.

No evidence of that.

Ray Fischer

From: John Sheehy on
ASAAR <caught(a)> wrote in

>> Sorry, I hit send before I finished that post. It should have read
>> "Anyone with any amount of experience in these matters would
>> recognize that even a magic lens with no softness of any kind would
>> pale next to the FZ50 lens and pixel density here, using the 400D and
>> scaling 289%.

> Sorry, but that doesn't make as much sense as the original.

Really? How are you going to overcome the nyquist of the lower pixel
density, or the reduced contrast near its nyquist caused by the AA filter?

Have any ideas?


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John P Sheehy <JPS(a)no.komm>
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