Megapixels to Sensor Sizes - Best Matches?

Paul D. Sullivan wrote:
> I read an article on Cnet about how 8 or 10 megapixel cameras are
> not as good as they could be because their megapixel capability
> does not match sensor sizes well. If you buy a camera with 8 or
> 10 megapixels and they have some really small sensor, the extra
> megapixels will not be realized in terms of quality.
>
> Got me thinking - what are some of the best matches of megapixel
> capability to sensor size?

While one can't prove there is an optimum, because the
trade space of size of a pixel versus performance just keeps
getting better with larger pixels, I personally think the
about 6 to 8 micron pixel pitch is the ideal size. That pitch
allows many pixels to be crammed into an small sensor
(e.g. about 8 megapixels in APS-C), while still collecting
enough photons for great performance, including high ISO
performance. Collecting about 50,000 photons per pixel
produces beautiful images, and the 6 to 6 micron pixel pitches
do that. This is the performance point of many DSLRs.

Quantitative data on sensor performance can be found at:
http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
>
> How does the Canon a640 mentioned in the article hold up?
>
> How does the Canon S3 IS hold up?

S3: 2-micron pixel pith: performance near the bottom of the range on the
plots on the above page.
>
> Olympus Evolt series with those 4/3rds sized sensors?

E300: 5.3 micron pitch should plot in the mid range of performance:
below most DSLRs and above most P&S.
>
> Do Fuji, Kodak, Nikon and others have a good ratio on average, or
> are certain models better than others?

Look at each model. The newer P&S cameras seem to cram in megapixels,
and performance per pixel suffers. Most notably, the high iso
performance (Figures 6 and 7 on the above web page).
>
> I'd like to think that consumers aren't getting screwed when they
> want to get to an 8 or 10 megapixel camera, and wanted to ask
> some of ya'all here about it so I could learn what up.
>
> Any helpful answers would be appreciated.
>
> Thanks

Manufacturers are trying to hide the noise and low performance
issues by average pixel in their noise reduction software. So what any
one camera produces out of camera can be confusing and the
manufacturers are trying to get you to think they have a better
solution. But CCD and CMOS sensors have noise dominated by photon
counting statistics over most of their range. That is a fundamental
limit, so collecting more photons with larger pixels is the only
major performance metric.

Other related info at:
http://www.clarkvision.com/imagedetail/index.html#sensor_analysis

Roger
Photos at: http://www.clarkvision.com
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

On Wed, 07 Feb 2007 14:46:45 +0000, Paul D. Sullivan wrote:

> I read an article on Cnet about how 8 or 10 megapixel cameras are
> not as good as they could be because their megapixel capability
> does not match sensor sizes well. If you buy a camera with 8 or
> 10 megapixels and they have some really small sensor, the extra
> megapixels will not be realized in terms of quality.
>
> Got me thinking - what are some of the best matches of megapixel
> capability to sensor size?
>
> How does the Canon a640 mentioned in the article hold up?
>
> How does the Canon S3 IS hold up?
>
> Olympus Evolt series with those 4/3rds sized sensors?
>
> Do Fuji, Kodak, Nikon and others have a good ratio on average, or
> are certain models better than others?
>
> I'd like to think that consumers aren't getting screwed when they
> want to get to an 8 or 10 megapixel camera, and wanted to ask
> some of ya'all here about it so I could learn what up.
>
> Any helpful answers would be appreciated.
>
> Thanks

FWIW - I remember two or three years ago reading that the latest crop of 8
mp cameras (pretty much state of the art then) were suffering from
crosstalk and not giving the results that had been anticipated.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

Yeah, that's kind of what that article was saying.

For me, I would want 8mp so I can get 300 dpi of resolvable
detail on 8x10 prints. I almost never go over 8x10, so figure
8mp is the sweet spot.

But I'd hate to think that extra 3 megapixels overy my 5
megapixel C5050 was simply "hot air" and not worth the
investment.

> FWIW - I remember two or three years ago reading that the
> latest crop of 8 mp cameras (pretty much state of the art
> then) were suffering from crosstalk and not giving the results
> that had been anticipated.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

On Thu, 08 Feb 2007 06:36:46 GMT, Paul D. Sullivan wrote:

> For me, I would want 8mp so I can get 300 dpi of resolvable
> detail on 8x10 prints. I almost never go over 8x10, so figure
> 8mp is the sweet spot.
>
> But I'd hate to think that extra 3 megapixels overy my 5
> megapixel C5050 was simply "hot air" and not worth the
> investment.

It's not hot air, but it may provide less than you expect. From
looking at some of dpreview's resolution tests for various cameras,
I'd say that based on the resolution of the 7mp sensor in Canon's
A620, the 10mp sensor in the A640 greater resolution, but only the
increase that you'd expect to see going from 7mp to 8mp. It may be
a different story for other cameras with other sensors.

It's very easy to see exactly what you'll get by going from the
C5050 to a specific camera with an 8mp sensor. Dpreview has a full
review for the C5050. Look at the resolution chart sections and the
studio scene comparisons. Some of the items will probably have
changed in the studio scenes over the years, but there should be
several that are still being used. Don't look at what appears on
the web page, but download the full sized studio scene images (not
all of them, just choose a couple of the better, low ISO versions).
These should each be several MB in size. Differences in resolvable
detail should be obvious using whatever program you normally use to
view photos on your computer. The last review web page shows a
sample image gallery containing pictures taken with the camera being
reviewed. These will be of different types of pictures more
representative of the shots real people take - no artificial test
images. So you can download a few of these for more comparisons.
These should show you exactly what you can expect from any of the
reviewed cameras. The best place to quickly find them is here:

http://www.dpreview.com/reviews/default.asp?view=alpha
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

That's a ton of data that I can't begin to understand. I wonder
if you would be so kind as to help summarize it in simpler terms?

For example, you indicate that the 4/3rds in the Oly Evolt is mid
range. That makes sense and I can understand that.

But I guess I'd further ask, what megapixel size is that sensor
able to resolve properly? Is 8 mp a good fit for that 4/3rds
sensor? Would it max out at 8 mp or would it also work well for
10 mp or 12 mp too?

Thanks much.

> While one can't prove there is an optimum, because the
> trade space of size of a pixel versus performance just keeps
> getting better with larger pixels, I personally think the
> about 6 to 8 micron pixel pitch is the ideal size. That pitch
> allows many pixels to be crammed into an small sensor
> (e.g. about 8 megapixels in APS-C), while still collecting
> enough photons for great performance, including high ISO
> performance. Collecting about 50,000 photons per pixel
> produces beautiful images, and the 6 to 6 micron pixel pitches
> do that. This is the performance point of many DSLRs.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

Thank you again. So the 10mp and sensor configuration in the
A640 really is not able to fully resolve those 10mp in a useful
or proper way? You are not truly getting the full possible
benefit from those 10 megapixels because the sensor is too small
inside the camera?

> It's not hot air, but it may provide less than you expect.
> From looking at some of dpreview's resolution tests for
> various cameras, I'd say that based on the resolution of the
> 7mp sensor in Canon's A620, the 10mp sensor in the A640
> greater resolution, but only the increase that you'd expect to
> see going from 7mp to 8mp. It may be a different story for
> other cameras with other sensors.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

On Thu, 08 Feb 2007 08:01:35 GMT, Paul D. Sullivan wrote:

> Thank you again. So the 10mp and sensor configuration in the
> A640 really is not able to fully resolve those 10mp in a useful
> or proper way? You are not truly getting the full possible
> benefit from those 10 megapixels because the sensor is too small
> inside the camera?

Not at all. I don't really understand how the 10mp sensor would
be considered to be not useful or not be able to resolve detail
properly. Some may say that it shows that Canon should have used a
larger sensor if they wanted to take the A6xx series up to 10mp, but
that probably would have been a mistake. It would have almost
certainly resulted in a camera that wasn't an incremental upgrade
from previous versions. The camera and lens probably would have
been larger. Someone owning a previous model such as the A610 or
A620 that had also purchased the wide or tele lens adapters may have
found themselves unable to use them with the A640. The A640's 10mp
sensor won't have the resolution of a good 10mp DSLR, but the
resolution it does provide is probably about as good as the
resolution you'd get from other 10mp P&S cameras using the same size
sensor. All I meant was to say that higher resolution alone is not
a good reason to upgrade, if you'll only be upgrading from a 7 or
8mp sensor, since the benefit is not as great as the numbers
indicate. The difference between the A640's 10mp sensor and any P&S
camera's 5mp sensor should be considerable, and the newer cameras
should also be faster, much easier on batteries, and have better
high ISO performance. The reviews indicate that even though more
pixels are squeezed into the same size sensor that is used by the
7mp sensor in the A620 (which I own), Canon has managed to do so
without degrading the image with more noise. My preference would
have been to keep the A640 at 7mp and try to reduce the noise (ie,
increase the usable ISO a notch or two). But other people might
prefer the higher resolution. An alternative would be to check out
the A630, the A640's smaller, less expensive 8mp sibling.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

Thanks for the clarification.

I guess it is hard to find some general rule of thumb about which
sensor size can properly handle what level of megapixels.

I guess I was hooping for something like this, for example:

"An Oly 4/3rds sensor is large enough to properly resolve a full
12 megapixels of image data - anything above that and you might
start to lose detail because the sensor cannot properly
accommodate more than 12 megapixels. In order to get higher than
12 megapixels and have those extra pixels be meaningful, they
would have to increase the size of the sensor"

But I guess it isn't that simple.

I do appreciate the reply. The more I read, the less that
article seems to be on target. They generalized too much, I
think.

Canon certainly seems to feel that the sensor in their 10mp A640
is fully capable of handling all 10mp of data properly, and
Olympus seems to feel very confident that the size of its 4/3rd
sensor is able to handle a full 8mp without any compromise in
quality.

Anyway, I'll keep on readin' - there is much to learn.

> themselves unable to use them with the A640. The A640's 10mp
> sensor won't have the resolution of a good 10mp DSLR, but the
> resolution it does provide is probably about as good as the
> resolution you'd get from other 10mp P&S cameras using the
> same size sensor.

> performance. The reviews indicate that even though more
> pixels are squeezed into the same size sensor that is used by
> the 7mp sensor in the A620 (which I own), Canon has managed to
> do so without degrading the image with more noise.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

On Feb 8, 11:48 am, "Paul D. Sullivan" <dudeb... DeleteThis @hotmail.com> wrote:
> Thanks for the clarification.
>
> I guess it is hard to find some general rule of thumb about which
> sensor size can properly handle what level of megapixels.
>
> I guess I was hooping for something like this, for example:
>
> "An Oly 4/3rds sensor is large enough to properly resolve a full
> 12 megapixels of image data - anything above that and you might
> start to lose detail because the sensor cannot properly
> accommodate more than 12 megapixels. In order to get higher than
> 12 megapixels and have those extra pixels be meaningful, they
> would have to increase the size of the sensor"

Well, the reason you don't get such an answer is probably that you
haven't defined the question carefully enough. There's not much
problem with these small sensors with lots of pixels, except for a)
noise, b) high pixel density which means the lens needs to resolve
many more line pairs/mm (at the sensor) than for eg a DSLR (which has
much larger pixels). The second problem is alleviated by the fact that
the sensor is smaller and thus the size of the image that must be
projected by the lens is also smaller, so that the lens doesn't cost
as much as one with equivalent resolution with a DSLR (or medium
format back!). On the other hand, I would have thought that not all
that much money and effort would be expended on making the lenses on
these compacts as sharp etc as possible, so probably some degradation
is also coming from there.

So, one cannot say "a sensor of size m cannot properly accomodate more
than n pixels", for the simple reason that you have not defined
"properly". If you say eg "this amount of noise is acceptable", then
probably a rough estimate can be found, or at least an upper limit for
n. But how do you plan to quantify it? Better to look at images and
decide.

There's not much else wrong with small sensors beside this noise
business (which can be a huge problem of course!), and of course there
are several advantages (cheaper and smaller lenses and cameras,
possiblity of having more versatile zooms with reasonable quality
etc). But a 10mp camera with a small sensor (such as the various
recent compacts) will always have more noise than a 10mp with a bigger
sensor (at least if they are both newer than, say, 2004).

>
> But I guess it isn't that simple.
>
> I do appreciate the reply. The more I read, the less that
> article seems to be on target. They generalized too much, I
> think.
>
> Canon certainly seems to feel that the sensor in their 10mp A640
> is fully capable of handling all 10mp of data properly, and
> Olympus seems to feel very confident that the size of its 4/3rd
> sensor is able to handle a full 8mp without any compromise in
> quality.

Well, as for handling the data, it's not a problem; the problem is to
actually collect it. But clearly if Canon did feel that the sensor
could handle 10mp with no problem, why do they produce cameras with
bigger ones? Do you really think that people pay 6-7000 euro for a
1Dmkwhateveritis just to be able to use their old lenses, if they
could get similar results otherwise? The differences, when they are
visible, can be huge, and so is the price difference!

>
> Anyway, I'll keep on readin' - there is much to learn.
>
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

Great reply. Thank you very much.

How does the Canon A640 hold up, if you don't mind? Does it give
a good combination for a 10 megapixel camera?

> Paul D. Sullivan wrote:
>> I read an article on Cnet about how 8 or 10 megapixel cameras
>> are not as good as they could be because their megapixel
>> capability does not match sensor sizes well. If you buy a
>> camera with 8 or 10 megapixels and they have some really
>> small sensor, the extra megapixels will not be realized in
>> terms of quality. Got me thinking - what are some of the best
>> matches of
>> megapixel capability to sensor size?
>
> While one can't prove there is an optimum, because the
> trade space of size of a pixel versus performance just keeps
> getting better with larger pixels, I personally think the
> about 6 to 8 micron pixel pitch is the ideal size. That pitch
> allows many pixels to be crammed into an small sensor
> (e.g. about 8 megapixels in APS-C), while still collecting
> enough photons for great performance, including high ISO
> performance. Collecting about 50,000 photons per pixel
> produces beautiful images, and the 6 to 6 micron pixel pitches
> do that. This is the performance point of many DSLRs.
>
> Quantitative data on sensor performance can be found at:
> http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
>>
>> How does the Canon a640 mentioned in the article hold up?
>>
>> How does the Canon S3 IS hold up?
>
> S3: 2-micron pixel pith: performance near the bottom of the
> range on the plots on the above page.
>>
>> Olympus Evolt series with those 4/3rds sized sensors?
>
> E300: 5.3 micron pitch should plot in the mid range of
> performance: below most DSLRs and above most P&S.
>>
>> Do Fuji, Kodak, Nikon and others have a good ratio on
>> average, or are certain models better than others?
>
> Look at each model. The newer P&S cameras seem to cram in
> megapixels, and performance per pixel suffers. Most notably,
> the high iso performance (Figures 6 and 7 on the above web
> page).
>>
>> I'd like to think that consumers aren't getting screwed when
>> they want to get to an 8 or 10 megapixel camera, and wanted
>> to ask some of ya'all here about it so I could learn what up.
>>
>> Any helpful answers would be appreciated.
>>
>> Thanks
>
> Manufacturers are trying to hide the noise and low performance
> issues by average pixel in their noise reduction software. So
> what any one camera produces out of camera can be confusing
> and the manufacturers are trying to get you to think they have
> a better solution. But CCD and CMOS sensors have noise
> dominated by photon counting statistics over most of their
> range. That is a fundamental limit, so collecting more
> photons with larger pixels is the only major performance
> metric.
>
> Other related info at:
> http://www.clarkvision.com/imagedetail/index.html#sensor_analysis
>
> Roger
> Photos at: http://www.clarkvision.com
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

On Feb 7, 8:46 am, "Paul D. Sullivan" <dudeb... RemoveThis @hotmail.com> wrote:
> I read an article on Cnet about how 8 or 10 megapixel cameras are
> not as good as they could be because their megapixel capability
> does not match sensor sizes well. If you buy a camera with 8 or
> 10 megapixels and they have some really small sensor, the extra
> megapixels will not be realized in terms of quality.
>
> Got me thinking - what are some of the best matches of megapixel
> capability to sensor size?
>
> How does the Canon a640 mentioned in the article hold up?
>
> How does the Canon S3 IS hold up?
>
> Olympus Evolt series with those 4/3rds sized sensors?
>
> Do Fuji, Kodak, Nikon and others have a good ratio on average, or
> are certain models better than others?
>
> I'd like to think that consumers aren't getting screwed when they
> want to get to an 8 or 10 megapixel camera, and wanted to ask
> some of ya'all here about it so I could learn what up.
>
> Any helpful answers would be appreciated.
>
> Thanks



It is the same situation as with film- "bigger is better". There used
to be an old saying- "nothing beats format size". While sometimes
people made higher acuity film for smaller formats, frequently the
film would gravitate up to larger formats.

With digicams bigger format size means larger aperture diameter at
same f/#, and collecting more photons during the same exposure time
period.

More expensive, of course. Silicon chips are more expensive when
larger, larger lenses needed for same field of view. But- better!
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

On Thu, 08 Feb 2007 06:56:35 GMT, "Paul D. Sullivan"
<dudeboyz.DeleteThis@hotmail.com> wrote:

>But I guess I'd further ask, what megapixel size is that sensor
>able to resolve properly? Is 8 mp a good fit for that 4/3rds
>sensor? Would it max out at 8 mp or would it also work well for
>10 mp or 12 mp too?

I think you're asking for objective answers to subjective questions.
How do you define "resolve properly"?
What is a "good fit"?
What does "work well" mean?

The answers will differ depending on who's asked. The end result is
that only you can answer these questions for yourself.
There are sites (such as, for example, dpreview.com) that offer sample
images from reviewed cameras, so that you can see for yourself how
these various cameras handle different conditions.
At such sites, you can see how well each camera handles the
compromises between different design goals; is 10MP on this camera
worth the trade-off in more noise? Or should you stick with the 8MP
model?
These are questions only you can answer; that's why there are so many
different makes and models out there; they offer different
combinations of compromises to attempt to meet the demands of as many
users as possible. But they aqre all compromises; there is no perfect
answer to your questions.

--
Massachusetts' former governor
Mitt Romney said Tuesday he will
announce his candidacy for the
GOP nomination for president next
week. He's a Mormon. It's not
expected to hurt him as long as
Rudy Giuliani is the candidate
with three wives.
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches? 

Paul D. Sullivan wrote:
> That's a ton of data that I can't begin to understand. I wonder
> if you would be so kind as to help summarize it in simpler terms?
>
> For example, you indicate that the 4/3rds in the Oly Evolt is mid
> range. That makes sense and I can understand that.
>
> But I guess I'd further ask, what megapixel size is that sensor
> able to resolve properly? Is 8 mp a good fit for that 4/3rds
> sensor? Would it max out at 8 mp or would it also work well for
> 10 mp or 12 mp too?

For each camera, first compute the pixel pitch. The pixel
pitch gives the best indicator of the active area of each pixel.
To compute pixel pitch, look up the size of the sensor
in mm. Many cameras have only an obscure size related to
vidicon vacuum tube size from over 50 years ago.
Sensor size conversion is here:
http://www.clarkvision.com/imagedetail/does.pixel.size.matter/index.ht...Sensor%

Let's say your camera has a 1/2.5 inch sensor. The above table
shows the real sensor size is 5.76 x 4.29 mm Now look up
the maximum size of images (not interpolated digital zoom)
the camera makes. For example the Canon S3 with a 1/2.5-inch sensor
gets 2816 x 2112 pixels. Take the size in mm times 1000 divide by
the number of pixels:

pixel pitch = long dimension in mm * 1000 / #pixels in long dimension

Canon S3 pixel pitch = 5.76 * 1000 / 2816 = 2.0 microns.

(there are 1000 microns per mm; the reason for the 1000 factor).

Now go to
http://www.clarkvision.com/imagedetail/digital.sensor.performance.summ.../index.

and plot a point in the gray band on Figure 2, 4 and 6 on the above
web page to get an idea of the camera performance, and how it
compares to other cameras. For example, on Figure 6, unity
gain ISO, 2-microns plots around ISO 100 in the gray band, the
bottom of performance. The unity gain ISO is the ISO where
1 digital number corresponds to 1 electron, so using higher ISO
is no help. This tells the high ISO performance of the camera.
If, for example, you want to take pictures indoors without flash of moving
subjects (baby's first step, kids and pets at play), you want unity gain
ISO to be as high as possible, with ISO 400 being a point where
images are reasonable quality (my opinion). In effect, ISO's higher
than the unity gain ISO is like "digital ISO." "Digital ISO,"
like digital zoom can be done in post processing and gains no
additional real image information. Camera manufacturers should
be able to publish unity gain ISOs on each camera in my
opinion.

Plotting points on Figure 2 will show image quality of a typical
well-exposed scene. You want to be in the 40 to 1 range or higher.
If the camera has ISO 50, the boost the numbers by 1.4x, so
ISO 100 giving signal-to-noise ratio (S/N) = 30 would give
30*1.4 = 42 at ISO 50 and good quality. If you do a lot of
editing (stretching, dodging and burning), you need higher
S/N. Also, if you want good shadow detail, you need good
S/N.

For total image quality, good lenses with high megapixel count
using larger pixels are best, but that makes for a larger (bulk and
weight) camera and higher cost. Only you can decide what
trade point you want/can afford.

Roger
>
> Thanks much.
>
>> While one can't prove there is an optimum, because the
>> trade space of size of a pixel versus performance just keeps
>> getting better with larger pixels, I personally think the
>> about 6 to 8 micron pixel pitch is the ideal size. That pitch
>> allows many pixels to be crammed into an small sensor
>> (e.g. about 8 megapixels in APS-C), while still collecting
>> enough photons for great performance, including high ISO
>> performance. Collecting about 50,000 photons per pixel
>> produces beautiful images, and the 6 to 6 micron pixel pitches
>> do that. This is the performance point of many DSLRs.
>
>
 >> Stay informed about: Megapixels to Sensor Sizes - Best Matches?