Sigma/Foveon Questions
 

Bubba wrote:
I don't understand how a sensor can claim 14 pixels, and the photo
itself be 4.

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

--
Ray Fischer

Sigma/Foveon Questions
 

Ray Fischer wrote:
Bubba wrote:
I don't understand how a sensor can claim 14 pixels, and the photo
itself be 4.

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

They don't lie. It's a different kind of sensor with sufficiently
different kinds of pixels and properties that the sensor megapixel
numbers aren't comparable with hose of Bayer sensors. It's like trying
to compare the engine capacities of ordinary car engines with
cylindrical pistons and rotary Wankel engines. The numbers have to
be normalised before you can make comparisons.

Of course it may well be the case that Foveon exaggerate a bit in
normalising their numbers. But then the megapixel numbers of Bayer
sensors are exaggerated themselves. An ordinary 14MP Bayer sensor
desn't give you the image resolution you'd expect from 14MP. Some gets
lost in the necessary AA filter. And that's not a constant, because
it's a trade off between detail resolution and aliasing
artefacts. Some makers give you more detail, in effect more megapixels
of detail, at the cost of more aliasing artefacts in the situations
where aliasing obtrudes.

So there's no simple way of normalising Foven megapixel numbers to
make them comparable to Bayer megapixel numbers. You simply have to
look at the results and make a subjective appraisal of comparability.
Just as you have to do when comparing Bayer megapixels from cameras
with different attitudes towards aliasing, such as Leica, Nikon, and
Hasselblad.

--
Chris Malcolm

Sigma/Foveon Questions
 

In article , Chris Malcolm
wrote:

I don't understand how a sensor can claim 14 pixels, and the photo
itself be 4.

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

They don't lie.

yes they do. calling it anything other than 4.6 or 4.7 megapixels is a
lie (it's actually 4.65, so either one is fine).

It's a different kind of sensor with sufficiently
different kinds of pixels and properties that the sensor megapixel
numbers aren't comparable with hose of Bayer sensors.

the difference is that bayer has one layer and foveon has three layers
per pixel. you don't get to count each layer as a separate pixel.

if you had a single pixel sensor with 1 million layers, would that be a
megapixel sensor? no.

It's like trying
to compare the engine capacities of ordinary car engines with
cylindrical pistons and rotary Wankel engines.

you can measure horsepower, torque and engine displacement for both.

The numbers have to
be normalised before you can make comparisons.

pixel is normalized.

Of course it may well be the case that Foveon exaggerate a bit in
normalising their numbers.

exaggerate a bit? they multiply it by 3. that's a lot.

But then the megapixel numbers of Bayer
sensors are exaggerated themselves.

no they're not.

An ordinary 14MP Bayer sensor
desn't give you the image resolution you'd expect from 14MP.

it does for me.

Some gets
lost in the necessary AA filter. And that's not a constant, because
it's a trade off between detail resolution and aliasing
artefacts. Some makers give you more detail, in effect more megapixels
of detail, at the cost of more aliasing artefacts in the situations
where aliasing obtrudes.

it doesn't matter how much detail there is in a photo, the number of
pixels on the sensor does not change.

So there's no simple way of normalising Foven megapixel numbers to
make them comparable to Bayer megapixel numbers.

yes there is.

You simply have to
look at the results and make a subjective appraisal of comparability.
Just as you have to do when comparing Bayer megapixels from cameras
with different attitudes towards aliasing, such as Leica, Nikon, and
Hasselblad.

sure, but the subjective quality doesn't change the number of pixels on
the sensor.

Sigma/Foveon Questions
 

In article
,
Bubba wrote:

At the risk of getting a rain of more invective on a day that's rainy
enough in my parts, does this mean that you can't...focus?!

focus and zoom are separate things.

assuming you are talking about the dp1/dp2 series, they can focus
(slowly), but there is no zoom. there is auto-focus, but as i said,
it's slow.

If you can
focus, there has to be *some* zoom (or is it just digital)?

there is no optical zoom. it's a fixed single focal length lens.

the dp1 has a 28mm equivalent lens and the dp2 has a 41mm equivalent.
if you want a focal length other than either of those, you're need a
different camera. sigma's strategy is to have you buy multiple cameras
for every focal length you want.

however, there is digital zoom and the sigma fanbois even claim that
the sensor is *so* good that digital zoom is just as good as optical
zoom (they really do say that).

These
Sigma owners, and the gentleman on another thread who recommended a
camera with a Foveon sensor to me, seem to use it for what I want it
for: nature photography in low light,

foveon is one of the worst choices for low light. it's noisy to begin
with but it gets really bad beyond iso 200.

without the artifacts that I
suppose you all here are calling "aliasing." (I've called it red
flare, because that's what I was told it was by the British folk on my
Serif editing software sight--a nicer bunch of people, I have not met
on any forum--including those on which I've tangled with nospam.)

red flare is not aliasing, however, the dp1/dp2 series have a red dot
problem, although the latest versions have minimized it.

Sigma/Foveon Questions
 

Chris Malcolm wrote:
Ray Fischer wrote:
Bubba wrote:
I don't understand how a sensor can claim 14 pixels, and the photo
itself be 4.

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

They don't lie. It's a different kind of sensor with sufficiently
different kinds of pixels and properties that the sensor megapixel

They lie.

When you measure the size of the image it produces you see that it is
4.6 mega pixels. That is the cold, hard fact. No amount of sophisty,
lies, or self-serving bull**** will alter that fact.

--
Ray Fischer

Sigma/Foveon Questions
 

In article
,
Bubba wrote:

red flare is not aliasing, however, the dp1/dp2 series have a red dot
problem, although the latest versions have minimized it.

If you're not yanking my chain and are serious when you use the term
"red flare"--which no one on the threads I've started has even
acknowledged exists--

this is the problem to which i refer:

http://www.testiweb.com/images/jpg/d...20dp1/Jpg%2095
0x%20or%20lower/foveon_flares_2_SDIM0025_950x.jpg
http://www.testiweb.com/images/jpg/d...20dp1/Jpg%2095
0x%20or%20lower/foveon_flares_3_SDIM0043_950x.jpg
http://raist3d.typepad.com/files/sigmanotoksunclouds.jpg

In a $500-$600 range, is a camera available that will lessen or do
away with red flare without the purchase of additional lenses or
filters?

plenty of them.

So if these wacky Sigma cameras have no zoom except digital, but if
their partisans swear by the cameras' sensors' ability to get rid of/
diminish this flare, that makes me ask Why would these people not want
another P&S camera that *has* optical zoom (or at least the ability to
attach a lens) AND a CMOS sensor.

they're delusional.

Sigma/Foveon Questions
 

In article
,
Bubba wrote:

Only the last link works, but I see what you mean. It looks like there
are red polka dots in the sun's rays.

try copy/pasting it if it wrapped, or just use these:
http://tinyurl.com/y5zam25
http://tinyurl.com/y46nhpj

In a $500-$600 range, is a camera available that will lessen or do
away with red flare without the purchase of additional lenses or
filters?

plenty of them.

I am familiar only with Canon products and do not understand this
Third-Fourths or Fourth-Third thing (if the term refers to CMOS
sensors). Canon offered me a "steady-date" discount on new equipment,
and I want to get a SX S1.

4/3rds is a smaller sensor than what's in nikon and canon slr cameras,
with a 2x crop factor versus 1.5 and 1.6.

the slrs based around the 4/3rds sensor weren't that much smaller than
the smallest nikon or canon slrs and never sold that well, but olympus
and panasonic have done away with the mirror box and now have what they
call micro-4/3rds, which is basically a large sensor compact camera.

So if these wacky Sigma cameras have no zoom except digital, but if
their partisans swear by the cameras' sensors' ability to get rid of/
diminish this flare, that makes me ask Why would these people not want
another P&S camera that *has* optical zoom (or at least the ability to
attach a lens) AND a CMOS sensor.

they're delusional.

Is that it?

what else could it be, when someone buys a sub-5 megapixel camera that
has noise and other problems and claims it is as good or better than an
18-24 megapixel camera?

it's one thing to like a certain look but it's another to claim things
that are simply not possible.

Sigma/Foveon Questions
 

Ray Fischer wrote:
Chris Malcolm wrote:
Ray Fischer wrote:
Bubba wrote:
I don't understand how a sensor can claim 14 pixels, and the photo
itself be 4.

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

They don't lie. It's a different kind of sensor with sufficiently
different kinds of pixels and properties that the sensor megapixel

They lie.

When you measure the size of the image it produces you see that it is
4.6 mega pixels. That is the cold, hard fact. No amount of sophisty,
lies, or self-serving bull**** will alter that fact.

Of course it doesn't. But I was talking about the image implications
of that fact. People are using image MP as a measure of image
quality. Different kinds of image sensor technology buy you different
amounts of image quality for the same number of pixels. If you look at
the two different methods that have to be used in order to translate
from sensor pixels to image pixels from the two kinds of sensor
technology you'll see there is an inherent difference in luminance
resolution, and a larger difference in chrominance resolution.

--
Chris Malcolm

Sigma/Foveon Questions
 

In article , Chris Malcolm
wrote:

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

They don't lie. It's a different kind of sensor with sufficiently
different kinds of pixels and properties that the sensor megapixel

They lie.

When you measure the size of the image it produces you see that it is
4.6 mega pixels. That is the cold, hard fact. No amount of sophisty,
lies, or self-serving bull**** will alter that fact.

Of course it doesn't.

so you agree they lie.

But I was talking about the image implications
of that fact. People are using image MP as a measure of image
quality.

it's a major factor but it's not the only one.

Different kinds of image sensor technology buy you different
amounts of image quality for the same number of pixels. If you look at
the two different methods that have to be used in order to translate
from sensor pixels to image pixels from the two kinds of sensor
technology you'll see there is an inherent difference in luminance
resolution, and a larger difference in chrominance resolution.

the luminance resolution is about the same as another 4.6 megapixel
sensor (alias artifacts is not resolution, it's false detail) and the
eye can't see the extra chroma resolution.

however, the point is that the number of pixels is still 4.6 million,
no matter what kind of image the sensor produces.

Sigma/Foveon Questions
 

Chris Malcolm wrote:
Ray Fischer wrote:
Chris Malcolm wrote:
Ray Fischer wrote:
Bubba wrote:
I don't understand how a sensor can claim 14 pixels, and the photo
itself be 4.

That's easy - Sigma lies. They pretend that you can take a single
pixel and split it up into three colors and have that be three pixels.

They don't lie. It's a different kind of sensor with sufficiently
different kinds of pixels and properties that the sensor megapixel

They lie.

When you measure the size of the image it produces you see that it is
4.6 mega pixels. That is the cold, hard fact. No amount of sophisty,
lies, or self-serving bull**** will alter that fact.

Of course it doesn't. But I was talking about the image implications
of that fact.

There aren't any. Sigma lies.

People are using image MP as a measure of image
quality.

People do all manner of stupid things. That doesn't justify lying.

--
Ray Fischer