FZ20 and image stabilization versus the larger sensor of the Sony 717

The Panasonic FZ20 has a 1/2.5 sensor while the Sony DSC-717 has a 2/3
sensor. The sensor area per pixel for the Sony is 2.8 times that for
the FZ20. This is equivalent to 1.5 stops. Thus I can set the ISO on
my Sony to between two and four times higher than on the Panasonic and
still get the same number of photons per pixel in a given light
situation. This means I can set the ISO on my Sony 2 to 4 times
higher and get the equivalent digital noise.

But this implies I can set my shutter to between 2 and 4 times faster.
It seems to me that I get the same handheld performance as the
Panasonic without the image stabilization.

Of course I don't get the same maximum telephoto, but with my
conversion telephoto lens, I almost do.

The bottom line is with a larger sensor, Panasonic wouldn't need image
stabilization.

"Martin" wrote in message
m...
The Panasonic FZ20 has a 1/2.5 sensor while the Sony DSC-717 has a 2/3
sensor. The sensor area per pixel for the Sony is 2.8 times that for
the FZ20. This is equivalent to 1.5 stops. Thus I can set the ISO on
my Sony to between two and four times higher than on the Panasonic and
still get the same number of photons per pixel in a given light
situation. This means I can set the ISO on my Sony 2 to 4 times
higher and get the equivalent digital noise.

I don't follow the argument here.

The amount of light falling on the sensor is a function of
the diameter of the lens as well as the size of the sensor.
If you increase the size of each pixel without increasing
the diameter of the lens, it would seem to me that you
would simply have to move the sensor further back from
the lens, and the number of photons falling on each
pixel would be identical to the number falling on a
smaller sensor set closer to the lens, but having the
same "effective" focal length.

If you are using, say, an f2.8 lens on each camera,
the number of photons per pixel should be identical
in each camera - whatever the pixel size.

There may be other factors which make the larger sensor
less noisy, but photons/pixel shouldn't be one of them.

Am I wrong? Don't hesitate to correct me, I've
certainly been wrong lots of times before.

Alan

But this implies I can set my shutter to between 2 and 4 times faster.
It seems to me that I get the same handheld performance as the
Panasonic without the image stabilization.

Of course I don't get the same maximum telephoto, but with my
conversion telephoto lens, I almost do.

The bottom line is with a larger sensor, Panasonic wouldn't need image
stabilization.

"Martin" wrote in message
m...
The Panasonic FZ20 has a 1/2.5 sensor while the Sony DSC-717 has a 2/3
sensor. The sensor area per pixel for the Sony is 2.8 times that for
the FZ20. This is equivalent to 1.5 stops. Thus I can set the ISO on
my Sony to between two and four times higher than on the Panasonic and
still get the same number of photons per pixel in a given light
situation. This means I can set the ISO on my Sony 2 to 4 times
higher and get the equivalent digital noise.

I don't follow the argument here.

The amount of light falling on the sensor is a function of
the diameter of the lens as well as the size of the sensor.
If you increase the size of each pixel without increasing
the diameter of the lens, it would seem to me that you
would simply have to move the sensor further back from
the lens, and the number of photons falling on each
pixel would be identical to the number falling on a
smaller sensor set closer to the lens, but having the
same "effective" focal length.

If you are using, say, an f2.8 lens on each camera,
the number of photons per pixel should be identical
in each camera - whatever the pixel size.

There may be other factors which make the larger sensor
less noisy, but photons/pixel shouldn't be one of them.

Am I wrong? Don't hesitate to correct me, I've
certainly been wrong lots of times before.

Alan

But this implies I can set my shutter to between 2 and 4 times faster.
It seems to me that I get the same handheld performance as the
Panasonic without the image stabilization.

Of course I don't get the same maximum telephoto, but with my
conversion telephoto lens, I almost do.

The bottom line is with a larger sensor, Panasonic wouldn't need image
stabilization.

For the same f-stop and focal length, the area of the lens aperture is
directly proportional to the area of the sensor. Thus the camera with
the 2/3 sensor has a larger lens than the camera with the 1/2.5 sensor
assuming both cameras have about the same maximum f-stop and samme
focal length. Thus it seems to me that Panasonic has traded off
sensor size and lens size for image stabilization. Perhaps a far
trade, I'm not sure.









"Alan Meyer" wrote in message ...
"Martin" wrote in message
m...
The Panasonic FZ20 has a 1/2.5 sensor while the Sony DSC-717 has a 2/3
sensor. The sensor area per pixel for the Sony is 2.8 times that for
the FZ20. This is equivalent to 1.5 stops. Thus I can set the ISO on
my Sony to between two and four times higher than on the Panasonic and
still get the same number of photons per pixel in a given light
situation. This means I can set the ISO on my Sony 2 to 4 times
higher and get the equivalent digital noise.

I don't follow the argument here.

The amount of light falling on the sensor is a function of
the diameter of the lens as well as the size of the sensor.
If you increase the size of each pixel without increasing
the diameter of the lens, it would seem to me that you
would simply have to move the sensor further back from
the lens, and the number of photons falling on each
pixel would be identical to the number falling on a
smaller sensor set closer to the lens, but having the
same "effective" focal length.

If you are using, say, an f2.8 lens on each camera,
the number of photons per pixel should be identical
in each camera - whatever the pixel size.

There may be other factors which make the larger sensor
less noisy, but photons/pixel shouldn't be one of them.

Am I wrong? Don't hesitate to correct me, I've
certainly been wrong lots of times before.

Alan

But this implies I can set my shutter to between 2 and 4 times faster.
It seems to me that I get the same handheld performance as the
Panasonic without the image stabilization.

Of course I don't get the same maximum telephoto, but with my
conversion telephoto lens, I almost do.

The bottom line is with a larger sensor, Panasonic wouldn't need image
stabilization.

"Martin" wrote in message
...
For the same f-stop and focal length, the area of the lens aperture is
directly proportional to the area of the sensor. Thus the camera with
the 2/3 sensor has a larger lens than the camera with the 1/2.5 sensor
assuming both cameras have about the same maximum f-stop and samme
focal length. Thus it seems to me that Panasonic has traded off
sensor size and lens size for image stabilization. Perhaps a far
trade, I'm not sure.

I think I understand you now.

Say two lenses are both rated f 2.8. One covers a 1 one square
inch sensor and the other a 1/3 square inch sensor. To achieve
f 2.8, the one covering the 1 square inch must have 3 times the
area of the one covering 1/3 sq. in. It therefore lets in 3 times as
much light. If both sensors have the same number of pixels, each
pixel in the 1 sq. in. sensor gets 3 times as much light.

In the film world, this is why large format cameras do not support
the fast lenses supported by 35 mm - because they can't make
lenses big enough to do it.

Makes sense.

Thanks for the explanation.

Alan

"Martin" wrote in message
...
For the same f-stop and focal length, the area of the lens aperture is
directly proportional to the area of the sensor. Thus the camera with
the 2/3 sensor has a larger lens than the camera with the 1/2.5 sensor
assuming both cameras have about the same maximum f-stop and samme
focal length. Thus it seems to me that Panasonic has traded off
sensor size and lens size for image stabilization. Perhaps a far
trade, I'm not sure.

I think I understand you now.

Say two lenses are both rated f 2.8. One covers a 1 one square
inch sensor and the other a 1/3 square inch sensor. To achieve
f 2.8, the one covering the 1 square inch must have 3 times the
area of the one covering 1/3 sq. in. It therefore lets in 3 times as
much light. If both sensors have the same number of pixels, each
pixel in the 1 sq. in. sensor gets 3 times as much light.

In the film world, this is why large format cameras do not support
the fast lenses supported by 35 mm - because they can't make
lenses big enough to do it.

Makes sense.

Thanks for the explanation.

Alan

"Martin" wrote in message
...
For the same f-stop and focal length, the area of the lens aperture is
directly proportional to the area of the sensor. Thus the camera with
the 2/3 sensor has a larger lens than the camera with the 1/2.5 sensor
assuming both cameras have about the same maximum f-stop and samme
focal length. Thus it seems to me that Panasonic has traded off
sensor size and lens size for image stabilization. Perhaps a far
trade, I'm not sure.

I think I understand you now.

Say two lenses are both rated f 2.8. One covers a 1 one square
inch sensor and the other a 1/3 square inch sensor. To achieve
f 2.8, the one covering the 1 square inch must have 3 times the
area of the one covering 1/3 sq. in. It therefore lets in 3 times as
much light. If both sensors have the same number of pixels, each
pixel in the 1 sq. in. sensor gets 3 times as much light.

In the film world, this is why large format cameras do not support
the fast lenses supported by 35 mm - because they can't make
lenses big enough to do it.

Makes sense.

Thanks for the explanation.

Alan