BASIC Question - Sensor size vs pixil size
Stromer2
1. Are the pixils in all camera sensors the same size?
2. Thus, do all cameras with the same MP rating have the same size sensor?
3. When a newer camera comes out with a larger MP sensor, is the sensor larger
than the older smaller MP sensor?
4. Why can't they just come out with a bigger sensor with more MP to give
better quality? Why not add two 6 MP sensors to get a 12 MP sensor? Is the
problem with this the processing power required? or cost because the sensor is
the most expensive part of the camera? Is the analogy to this the ever
increasing speed of computer microprocessors or memory size getting larger for
lower cost?
Thanks for inputs to this topic. I am very curious about how digital cameras
work.
Thank you, Rick
Don Cohen
You're technically correct, although in "common usage" I think people can
understand pixel size in the physical context here as being the sensor area
divided by the number of pixels. The D30 has the same sensor size as the
D60, while the D60 has twice the number of pixels. In this sense, "pixel
size" would be smaller in the D60 (?by a factor of 2 in terms of area?).
But again you're correct that it's the size of the individual sensor that
varies.
One other consideration is that people who know more than I about the
electronics involved indicate that to some degree, the larger the individual
sensor elements, the less electronic noise, and the 'smoother' the image.
I'm sure there are other variables that effect this as well, so it's not an
absolute element, but may enter into the end result.
--
Don
Photo Website at:
http://www.dlcphotography.net
[Remove the "lens cap" for email]
"Jim Townsend" <Xj...@escape.ca> wrote in message
news:udjvmi9...@news.supernews.com...
> Stromer2 wrote:
>
> > I would like to ask these questions to all of the experts on this
> > thread. 1. Are the pixils in all camera sensors the same size?
>
> Pixels have no size.. This is an important concept to grasp.
>
> If you look at camera specs they ONLY talk about the number of
> Pixels... X and Y. NOWHERE do you see any reference to the size of
> the pixels... That measurment doesn't exist. Pixels have no size.
>
> An imaging device has a grid of individual sensors that generate
> pixels. These individual sensors *do* have a physical size..
>
> The smaller the individual sensor, the more pixels the imaging device
> can generate. Conversely, the larger the individual sensors, the
> fewer pixels the device can generate.
>
> In 35mm film, you want the lens to focus on an area the size of the
> negative.. With digital imaging, you want to have the lens focus on
> an area the size of the imaging device.. The more individual sensors
> you have on the device, the more pixels will be generated. More
> pixels = better resolution and the ability to make larger prints.
>
>
bfu...@no-spam.pippinf.com
>I would like to ask these questions to all of the experts on this thread.
>1. Are the pixils in all camera sensors the same size?
>2. Thus, do all cameras with the same MP rating have the same size sensor?
These seem to be related.
If two sensor have the same number of pixels, the larger sensor will
have the larger pixel cells.
However, as far as a photo image file is concerned, there is no "size"
to a pixel. The image has so-many-pixels by so-many-pixels in it; how
large the image will be depends entirely on how it is displayed.
>3. When a newer camera comes out with a larger MP sensor, is the sensor larger
>than the older smaller MP sensor?
The number of pixels in a sensor is not tied to sensor size. Many 3 MP
zsensors are the same size as 2 MP sensors; even many 4 MP sensors are
the same physical size of many 2 MP sensors.
So, no, more MP does not necessarily mean larger sensor size.
>4. Why can't they just come out with a bigger sensor with more MP to give
>better quality? Why not add two 6 MP sensors to get a 12 MP sensor? Is the
>problem with this the processing power required? or cost because the sensor is
>the most expensive part of the camera? Is the analogy to this the ever
>increasing speed of computer microprocessors or memory size getting larger for
>lower cost?
Larger sensors mean higher costs. The sensors are cut from silicon
wafers, and the larger the sensor is, then fewer can be cut from a
wafer, raising the cost.
Two 6 MP sensors would not make for a file size anywhere near the LxW
ratio we are used to. A single 12 MP sensor will be much better.
CPU speed isn't related to this at all. In CPU's, smaller size meand
less power used, which in turn means less heat. Thus, the drive to
smaller and smaller die sizes.
With an image sensor, smaller size means less area per cell to gather
photons, thus less sensitivity to light, a bad thing.
A larger sensor would mean larger cells, meaning more light
sensitivity, meaning less noise and higher possible ISA numbers, as
well as a better fit with existing 35mm lenses. It also means higher
costs, which is, I think, one of the main reasons we don't see sensors
the size of a 35mm frame in current consumer digital cameras.
>Thanks for inputs to this topic. I am very curious about how digital cameras
>work.
>Thank you, Rick
-
Bill Funk
www.pippinf.com
Del Stanton
>
sensors together to make a 12 MP camera. Surely a sensor must be
designed with some sort of border surrounding the sensitive area.
I have no idea of what the reject rate is in sensor manufacture, but
doubling the sensor area would tend to double the reject rate. (More
pixels - more chances for bad pixels.) If the reject rate is 1% then
a doubling would not be very expensive for the manufacturer. If the
reject rate is 15% then doubling the sensor size increases it to 30%.
That would make the sensors much more expensive.
Manufacturers work hard to optimize their products for features and
cost in competitive markets. The digital still camera market is now
very large and many manufacturers are reaching for the brass ring. And
in the next five years it will probably double or triple in number of
cameras sold. So there will be lots of new camera, higher pixel
cameras and so forth.
I suspexct the average point and shoot photographer will wait until a
digital camera costs about $150 and it is ridiculously easy to
transfer pictures from the camera to his computer. I see the Kodak
camera dock as a step in that direction. But that user seldom gets
more thjan 4 x 6 inch prints from the photofishier and will probably
be quite happy with a 2 MP camera. Even at that size the pictures are
too big to view on a 1024 x 768 pixel monitor !
Del Stanton sd...@earthlink.net
On 09 May 2002 04:19:35 GMT, stro...@aol.com (Stromer2) wrote:
Jerome Bigge
>Stromer2 wrote:
>
>> I would like to ask these questions to all of the experts on this
>> thread. 1. Are the pixils in all camera sensors the same size?
>
>Pixels have no size.. This is an important concept to grasp.
>
>If you look at camera specs they ONLY talk about the number of
>Pixels... X and Y. NOWHERE do you see any reference to the size of
>the pixels... That measurment doesn't exist. Pixels have no size.
>
>An imaging device has a grid of individual sensors that generate
>pixels. These individual sensors *do* have a physical size..
>
>The smaller the individual sensor, the more pixels the imaging device
>can generate. Conversely, the larger the individual sensors, the
>fewer pixels the device can generate.
>
>In 35mm film, you want the lens to focus on an area the size of the
>negative.. With digital imaging, you want to have the lens focus on
>an area the size of the imaging device.. The more individual sensors
>you have on the device, the more pixels will be generated. More
>pixels = better resolution and the ability to make larger prints.
>
The manufacturers are increasing the number of pixels per the
same area of the sensor. For example, the Olympus D-370 was
1.3 megapixels, the new Olympus D-380 is 2 megapixels. Both
cameras use the exact same focal length lens, (4.5mm) which
is supposed to equal a 35mm on a 35mm film camera. This is
much like what the film manufacturers have done with film, that
is, giving you a finer grain structure so that the picture is less
"grainy" at any certain size.
Jerome Bigge
NRA Life Member
Supporter of National Health Insurance
CompTIA A+ Certified Computer Technician
Author of the "Warlady" & "Wartime" series.
Download at "http://members.tripod.com/~jbigge"
Don Stauffer
professional astronomers that were intended to be butted together. They
brought off all leads to two adjacent sides. That left the other two
sides available for butting, and they were butted together in a 2 x 2
(four chip) arrangement. But these were very special, very expensive,
and only doubled the linear resolution. I suspect also that there was
still an artifact where the sides butted together.
Del Stanton wrote:
>
> >Why not add two 6 MP sensors to get a 12 MP sensor?
> >
> I do not think it would be physically possible to butt two 6 MP
> sensors together to make a 12 MP camera. Surely a sensor must be
> designed with some sort of border surrounding the sensitive area.
>
--
Don Stauffer in Minnesota
stau...@usfamily.net
webpage- http://www.usfamily.net/web/stauffer
Thomas
> 4. Why can't they just come out with a bigger sensor with more MP to give
> better quality? Why not add two 6 MP sensors to get a 12 MP sensor?
ISTR there was a Minolta which worked this way. Optically split the
image and direct towards 2 CCDs that actually were some distance apart.
Thomas
Leonard Evens
<Xj...@escape.ca> wrote:
> Stromer2 wrote:
>
>> I would like to ask these questions to all of the experts on this
>> thread. 1. Are the pixils in all camera sensors the same size?
>
> Pixels have no size.. This is an important concept to grasp.
>
> If you look at camera specs they ONLY talk about the number of Pixels...
> X and Y. NOWHERE do you see any reference to the size of the pixels...
> That measurment doesn't exist. Pixels have no size.
>
> An imaging device has a grid of individual sensors that generate pixels.
> These individual sensors *do* have a physical size..
>
> The smaller the individual sensor, the more pixels the imaging device
> can generate. Conversely, the larger the individual sensors, the fewer
> pixels the device can generate.
What you say here is basically correct, but there is one other
possibility. Most digital cameras today have sensor arrays
approximately one fourth to one fifth the size of a 35 mm frame
(24 x 36 mm). If the sensor array size stays fixed, the more sensor
elements, the smaller each element has to be. But there is also the
option of increasing the size of the sensor array, so more sensor
elements of the same size will fit. The most expensive Canon digital
cameras have sensor arrays which are more than one half the size of a 35
mm frame. With such a camera, standard Canon lenses may be used,
although they then have smaller angles of view and act like longer focal
length 35 mm lenses for the standard frame size.
There is also a good reason to use larger sensor arrays. Lenses are
limited by diffraction at higher f-numbers, and this effect is
independent of focal length. The smaller the light sensitive array, the
more the image has to be magnified for a useful picture. That magnifies
the effect of diffraction. It is true that the shorter focal length
lenses in digital cameras have greater depth of field for the same angle
of view and same f-number, so to some extent the diffraction problem can
be avoided simply by limiting the highest f-number available. But the
manufacturers have not been able to produce acceptable lenses with very
small f-numbers for these cameras, so the net result is that the range of
f-numbers available is reduced. One solution to this problem is to use
larger sensor arrays.
As digital technology proceeds, I think we may find it moving towards
something like the situation for film photography. There will be a
common format for general use by amateurs for "snapshots" which will
approximate point and shoot 35 mm film photography, there will be larger
formats for general professional use of the quality of today's medium
format photography, and there will be large formats for the highest
quality art photography and commercial photography requiring the use of
view cameras. What these sizes will be is not clear, but they will
probably be somewhat smaller than the current film formats in use today.
>
> In 35mm film, you want the lens to focus on an area the size of the
> negative.. With digital imaging, you want to have the lens focus on an
> area the size of the imaging device.. The more individual sensors you
> have on the device, the more pixels will be generated. More pixels =
> better resolution and the ability to make larger prints.
>
>
--
Leonard Evens l...@math.northwestern.edu 847-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208
Jeepnik
I've been using film for quite some time and I'm interested in starting
with digital. What you have written is one of the most lucid explanations
of pixels vs. sensor array size with a comparison to 35mm. I just want to
say thank you. You cleared up quite a few questions, but of course raise
many more.
"Leonard Evens" <l...@math.northwestern.edu> wrote in message > What you say