"The exposures are at 1/100,000,000ths of a second"

In article , William Graham
writes

I don't know how I would go about building a shutter that could take a
picture at one, one millionth of a second. Also, I don't think that kind of
speed would be necessary. After all, the blast can't be that much brighter
than the sun, which is simply a continuous nuclear explosion.

Oh yes it can!

So, taking a
picture of a nuclear blast would be like taking a photograph of the sun.

What you see when you look at the sun is not actually the nuclear
reaction, but the photosphere, which is hot gases at about 5300degC but
considerably colder than the 10 million or so degC at the heart of the
sun where the nuclear reactions are occurring. Just remember that the
only thing that stops the sun from collapsing under its own weight is
the pressure produced in the core by the nuclear generated light - that
is a lot of light.

There are lots of things that are brighter than the sun here on earth,
and they don't need to be nuclear sources. My hefty old flashgun, for
example, has a flash duration at full power of 1/250th of a second and
ISO100 GN of 56. So it produces enough light to match the "sunny 16
rule" at about 1m range - making it just as bright at that range as the
sun for the time it is lit. Half a metre and it is 4 times brighter
than the sun, and so on.

It's true that it isn't the brightness that they were worried about, but the
ability to freeze the motion. So the question is, how fast must the shutter
be in order to do this, and do they have film that is fast enough to record
it at that speed. I think that a millionth of a second is way too fast to
answer either question. IOW, they don't need that kind of speed to freeze
the motion, and even if they did, they don't have any film fast enough to be
able to record the event at that speed. We certainly don't have any film
fast enough to record the sun at a millionth of a second, do we? Most high
speed photographs are frozen in time by the strobe light, and not by the
shutter.

So, what you are saying is that the strobe light used to capture such
images must be many times brighter at the scene than the sun would be,
which is certainly true, as witnessed by the rough estimate given above.
But even those powerful strobes are trivially dim compared to a nuclear
flash.

In other words, your own observation contradicts what you are asserting
- there certainly did have enough light for that shutter speed, and at
quite a large f/# as well I expect, given that this is a 10ft focal
length optic! ;-)
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

"Kennedy McEwen" wrote in message
...
In article , William Graham
writes

I don't know how I would go about building a shutter that could take a
picture at one, one millionth of a second. Also, I don't think that kind
of
speed would be necessary. After all, the blast can't be that much brighter
than the sun, which is simply a continuous nuclear explosion.

Oh yes it can!

So, taking a
picture of a nuclear blast would be like taking a photograph of the sun.

What you see when you look at the sun is not actually the nuclear
reaction, but the photosphere, which is hot gases at about 5300degC but
considerably colder than the 10 million or so degC at the heart of the sun
where the nuclear reactions are occurring. Just remember that the only
thing that stops the sun from collapsing under its own weight is the
pressure produced in the core by the nuclear generated light - that is a
lot of light.

There are lots of things that are brighter than the sun here on earth, and
they don't need to be nuclear sources. My hefty old flashgun, for
example, has a flash duration at full power of 1/250th of a second and
ISO100 GN of 56. So it produces enough light to match the "sunny 16 rule"
at about 1m range - making it just as bright at that range as the sun for
the time it is lit. Half a metre and it is 4 times brighter than the sun,
and so on.

It's true that it isn't the brightness that they were worried about, but
the
ability to freeze the motion. So the question is, how fast must the
shutter
be in order to do this, and do they have film that is fast enough to
record
it at that speed. I think that a millionth of a second is way too fast to
answer either question. IOW, they don't need that kind of speed to freeze
the motion, and even if they did, they don't have any film fast enough to
be
able to record the event at that speed. We certainly don't have any film
fast enough to record the sun at a millionth of a second, do we? Most high
speed photographs are frozen in time by the strobe light, and not by the
shutter.

So, what you are saying is that the strobe light used to capture such
images must be many times brighter at the scene than the sun would be,
which is certainly true, as witnessed by the rough estimate given above.
But even those powerful strobes are trivially dim compared to a nuclear
flash.

In other words, your own observation contradicts what you are asserting -
there certainly did have enough light for that shutter speed, and at quite
a large f/# as well I expect, given that this is a 10ft focal length
optic! ;-)

So all I guess I need to know is how to get a 1/millionth second
shutter.....I don't know how to rotate a polarizer that fast, and I don't
understand the other faraday reference.....I know that I used to use a
Tectronics capture scope that couldn't even blank off the erase pulse, which
used to destroy my vision in a darkened room every few seconds.....I don't
know why they didn't blank that off with a standard mechanical shutter, much
less a millionth second electronic one.....

"William Graham" wrote in message
...

"Kennedy McEwen" wrote in message
...
In article , William Graham
writes

I don't know how I would go about building a shutter that could take a
picture at one, one millionth of a second. Also, I don't think that kind
of
speed would be necessary. After all, the blast can't be that much
brighter
than the sun, which is simply a continuous nuclear explosion.

Oh yes it can!

So, taking a
picture of a nuclear blast would be like taking a photograph of the sun.

What you see when you look at the sun is not actually the nuclear
reaction, but the photosphere, which is hot gases at about 5300degC but
considerably colder than the 10 million or so degC at the heart of the
sun where the nuclear reactions are occurring. Just remember that the
only thing that stops the sun from collapsing under its own weight is the
pressure produced in the core by the nuclear generated light - that is a
lot of light.

There are lots of things that are brighter than the sun here on earth,
and they don't need to be nuclear sources. My hefty old flashgun, for
example, has a flash duration at full power of 1/250th of a second and
ISO100 GN of 56. So it produces enough light to match the "sunny 16
rule" at about 1m range - making it just as bright at that range as the
sun for the time it is lit. Half a metre and it is 4 times brighter than
the sun, and so on.

It's true that it isn't the brightness that they were worried about, but
the
ability to freeze the motion. So the question is, how fast must the
shutter
be in order to do this, and do they have film that is fast enough to
record
it at that speed. I think that a millionth of a second is way too fast to
answer either question. IOW, they don't need that kind of speed to freeze
the motion, and even if they did, they don't have any film fast enough to
be
able to record the event at that speed. We certainly don't have any film
fast enough to record the sun at a millionth of a second, do we? Most
high
speed photographs are frozen in time by the strobe light, and not by the
shutter.

So, what you are saying is that the strobe light used to capture such
images must be many times brighter at the scene than the sun would be,
which is certainly true, as witnessed by the rough estimate given above.
But even those powerful strobes are trivially dim compared to a nuclear
flash.

In other words, your own observation contradicts what you are asserting -
there certainly did have enough light for that shutter speed, and at
quite a large f/# as well I expect, given that this is a 10ft focal
length optic! ;-)

So all I guess I need to know is how to get a 1/millionth second
shutter.....I don't know how to rotate a polarizer that fast, and I don't
understand the other faraday reference.....I know that I used to use a
Tectronics capture scope that couldn't even blank off the erase pulse,
which used to destroy my vision in a darkened room every few seconds.....I
don't know why they didn't blank that off with a standard mechanical
shutter, much less a millionth second electronic one.....

Ah......I found some information on it he

http://www.rit.edu/~andpph/text-high-speed.html

Magneto-optical Shutter

This utilizes the Faraday effect, i.e., the rotation of the plane of
polarization of light passing through a transparent medium in a magnetic
field.

To use the Faraday effect, a suitable medium in a magnetic coil is placed
between crossed polarizers. Dense flint glass is generally used, since it
shows considerable rotation of the plane of polarization for a given
magnetic field and is convenient to handle. With no current in the coil,
there is no magnetic field, no rotation of the plane of polarization occurs,
and therefore no light is transmitted. When a suitable current is applied
(often 1,000 amperes needing 10,000 volts) the plane of polarization is
rotated until it agrees with the second polarizer, and the maximum light is
transmitted. This current can be supplied by discharging a capacitor through
the coil using a spark gap as a switch. The time of the discharge depends on
the capacitor size, the voltage, and the number of turns in the coil.
Exposure times down to 1 microsecond have been achieved.

Andy Williams wrote:

William Graham wrote:


I don't know how I would go about building a shutter that could take a
picture at one, one millionth of a second.


It is not a shutter in the ordinary mechanical sense, of course. It's
an electronic effect. Google Kerr effect.


Also, I don't think that kind of
speed would be necessary. After all, the blast can't be that much brighter
than the sun, which is simply a continuous nuclear explosion. So, taking a
picture of a nuclear blast would be like taking a photograph of the sun.


You are ignoring the inverse square law. The Sun is 93 million miles
away. A nuclear explosion can be photographed from seven miles away.
The fireball is about 60 - 100 million degrees C, 10,000 times hotter
and about 10^16 times brighter than the surface of the sun.

And the reason for the millionth of a second "shutter speeds" isn't to
deal with the brightness, but to deal with TIME.

They wanted discrete images of the fireball in very small increments of
time, so they could see how it developed.

In article , William Graham
writes


So all I guess I need to know is how to get a 1/millionth second
shutter.....I don't know how to rotate a polarizer that fast, and I don't
understand the other faraday reference.....I know that I used to use a
Tectronics capture scope that couldn't even blank off the erase pulse, which
used to destroy my vision in a darkened room every few seconds.....I don't
know why they didn't blank that off with a standard mechanical shutter, much
less a millionth second electronic one.....

The Kerr cell is only one way of achieving this sort of shutter time. I
posted a link to a gated intensifier camera the other day with a 10nS
gate period (which is the electronic equivalent of the shutter).

http://www.linuxdevices.com/articles/AT2171151224.html

I worked with a similar system based on an intensified isocon camera for
low light imaging back in the early 80's, although that had been in
service with the RAF for at least a decade by then.

There are equivalent solid state devices available these days, some of
which are used for laser gated imaging, for example in cost effective
undersea surveillance from an aircraft. In such systems the rapid
shutter speed, coupled to a pulsed laser illumination source, permits
the camera shutter to be closed when the laser pulse is reflected by the
sea surface, but opened when the reflection from the sea bed returns.
This effectively eliminated the reflection from the ocean surface from
the images, permitting clear images of the sea bed to be obtained.
Obviously, since the sea water rapidly attenuates the laser light there
are limits as to how deep you can image, hence the need for high
sensitivity as well as fast shutter speed.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

"William Graham" writes:

So all I guess I need to know is how to get a 1/millionth second
shutter.....I don't know how to rotate a polarizer that fast, and I don't
understand the other faraday reference.....

You need a substance that changes the amount it rotates polarized light
depending on the voltage applied. Liquid crystals work that way, but
they're too slow for this use. But there are other faster
technologies.

I know that I used to use a
Tectronics capture scope that couldn't even blank off the erase pulse, which
used to destroy my vision in a darkened room every few seconds.....I don't
know why they didn't blank that off with a standard mechanical shutter, much
less a millionth second electronic one.....

And how would you go about that? The erase is done by flooding the
screen with electrons for a significant fraction of a second, to
equalize the charge on the storage grid behind the screen. The only way
to block that is have a shutter between your eye and the screen - which
means a full-screen-sized shutter (impractical if mechanical, expensive
if electronic), or forcing you to look through a small hole that can
have a small shutter protecting it.

Anyway, aren't you glad that these have mostly been replaced by digital
storage? Now the image doesn't degrade no matter how long you look at
it, and you don't get fainter images at faster writing speeds, and you
can even print the waveform or save it on your PC, instead of having to
photograph it on film before it decayed. (See, there's a camera in this
posting after all).

Dave

David Littlewood writes:

Anyone seriously interested in the general subject of high-speed
photography may care to get hold of a copy of "High Speed Photography
and Photonics", Ed Sidney F Ray, Focal Press 1997, ISBN 0 2405 1479 3
(The may be a later edition for all I know.

If you find yourself in London England with some time to kill, there are
examples of some of these very high-speed cameras in the Photography
section of the Science Museum, located in South Kensington.

(There might well be some in the National Museum of Photography, Film,
and Television in Bradford too; I wasn't there long enough to see its
whole collection).

Dave

"Kennedy McEwen" wrote in message
...
In article , William Graham
writes


So all I guess I need to know is how to get a 1/millionth second
shutter.....I don't know how to rotate a polarizer that fast, and I don't
understand the other faraday reference.....I know that I used to use a
Tectronics capture scope that couldn't even blank off the erase pulse,
which
used to destroy my vision in a darkened room every few seconds.....I don't
know why they didn't blank that off with a standard mechanical shutter,
much
less a millionth second electronic one.....

The Kerr cell is only one way of achieving this sort of shutter time. I
posted a link to a gated intensifier camera the other day with a 10nS gate
period (which is the electronic equivalent of the shutter).

http://www.linuxdevices.com/articles/AT2171151224.html

I worked with a similar system based on an intensified isocon camera for
low light imaging back in the early 80's, although that had been in
service with the RAF for at least a decade by then.

There are equivalent solid state devices available these days, some of
which are used for laser gated imaging, for example in cost effective
undersea surveillance from an aircraft. In such systems the rapid shutter
speed, coupled to a pulsed laser illumination source, permits the camera
shutter to be closed when the laser pulse is reflected by the sea surface,
but opened when the reflection from the sea bed returns. This effectively
eliminated the reflection from the ocean surface from the images,
permitting clear images of the sea bed to be obtained. Obviously, since
the sea water rapidly attenuates the laser light there are limits as to
how deep you can image, hence the need for high sensitivity as well as
fast shutter speed.

Yes. that would be an excellent use of a super fast shutter. It is similar
to the problem of the power pulse in a radar set burning out the sensitive
receiver that must be attached to the same waveguide to capture the much
lower intensity received pulse. Basically this was accomplished by "shorting
out" the waveguide path to the receiver, using the power pulse itself to do
the shorting......

"Dave Martindale" wrote in message
...
"William Graham" writes:

So all I guess I need to know is how to get a 1/millionth second
shutter.....I don't know how to rotate a polarizer that fast, and I don't
understand the other faraday reference.....

You need a substance that changes the amount it rotates polarized light
depending on the voltage applied. Liquid crystals work that way, but
they're too slow for this use. But there are other faster
technologies.

I know that I used to use a
Tectronics capture scope that couldn't even blank off the erase pulse,
which
used to destroy my vision in a darkened room every few seconds.....I don't
know why they didn't blank that off with a standard mechanical shutter,
much
less a millionth second electronic one.....

And how would you go about that? The erase is done by flooding the
screen with electrons for a significant fraction of a second, to
equalize the charge on the storage grid behind the screen. The only way
to block that is have a shutter between your eye and the screen - which
means a full-screen-sized shutter (impractical if mechanical, expensive
if electronic), or forcing you to look through a small hole that can
have a small shutter protecting it.

Anyway, aren't you glad that these have mostly been replaced by digital
storage? Now the image doesn't degrade no matter how long you look at
it, and you don't get fainter images at faster writing speeds, and you
can even print the waveform or save it on your PC, instead of having to
photograph it on film before it decayed. (See, there's a camera in this
posting after all).

Dave

Yes. (I am glad) But even at the time I was doing this (some thirty years
ago) they had all the time in the world to shutter off that erase pulse. I
could have done it with a motor driven window shade..:^) I did get rather
good at simply closing my eyes during the erase time.......

In article , William Graham
writes

It is similar
to the problem of the power pulse in a radar set burning out the sensitive
receiver that must be attached to the same waveguide to capture the much
lower intensity received pulse.

A similar effect to the laser back-scatter from close range atmospheric
suspensions swamping out the much lower intensity signals from the
scene. This is quite common on laser illuminated systems and the gated
sensor is a neat solution.

There is a classic example of this shown he
http://www.obzerv.com/video/Snowfall_large.html

In this case the image is totally obscured by reflections from the close
range falling snow, in fact the snow is falling so heavily that it would
obscure the scene in any case. However, by extending the delay between
the laser firing and the sensor gate (shutter) opening, the sensor can
suddenly see right through the falling snow without significant loss of
contrast.

There were times when I was shooting in smoke filled rooms years ago
when this technology would have been most welcome. Fortunately, that
particular form of pollution has diminished - and in some places become
illegal - so it is less of an issue for photographers these days.

Basically this was accomplished by "shorting
out" the waveguide path to the receiver, using the power pulse itself to do
the shorting......

Actually, in the solid state devices I referred to, that is almost
exactly what is done - the storage well is effectively shorted out until
the start of the gate. All of which goes to show that there is nothing
new. ;-) Controlling the back edge of the gate is a lot trickier
though. ;-)
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)