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

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

Rich
Guest
Posts: n/a

 02-21-2006
On Sun, 19 Feb 2006 23:09:08 GMT, no_name <(E-Mail Removed)>
wrote:

>Kennedy McEwen wrote:
>
>> In article <Y91Kf.467\$(E-Mail Removed)>, Alan Browne
>> <(E-Mail Removed)> writes
>>
>>>
>>> My Maxxum 9 has a mechanical shutter speed of 1/12,000 of a second.
>>> Only 83 times slower than 1/1,000,000. It is a moving slit of the
>>> curtains in the camera.
>>>

>> But the slit takes about 1/250th sec to traverse the entire frame. The
>> fireball would be out by the time the first exposure was complete!
>> Similar problem with the idea of the slit in a rotating disk, although
>> with a big enough disk the slit could be larger than the frame size.

>
>multiple slits & multiple frames on a counter-spinning film disk? As the
>slit crosses the aperature clockwise, the film frame crosses the
>aperature counter-clockwise.
>
>If they were a large enough diameter & spinning fast enough.
>
>I'm not saying this is how they did it, just that it could be done.
>Although it sounds like a serious kludge.

They could synchronize machine guns so they didn't blow
the propellers off fighters in WW2, so making a multi slit camera
mechanism should be simple.
-Rich

Colin D
Guest
Posts: n/a

 02-21-2006

Alan Browne wrote:
>
> Colin D wrote:
>
> >
> > Alan Browne 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.
> >>
> >>My Maxxum 9 has a mechanical shutter speed of 1/12,000 of a second.
> >>Only 83 times slower than 1/1,000,000. It is a moving slit of the
> >>curtains in the camera. It is complex as the shutter is composed of
> >>seperate titanium blades that have to moves
> >>
> >>At 1/12,000 of a second, to cover 24mm (a bit more), the slit velocity
> >>is about 288 m/sec or 1036 km/hr (about 650 mph). (That's the shutter
> >>velocity at all shutter speeds, actually).
> >>

> >
> > Uhh, Alan, the blinds travel more slowly than that. It's the uncovered
> > time sensor that is 1/12,000 second, not the total travel time. If for
> > example, the slit between first and second blinds is 1 mm, the slit
> > velocity will be 1/24 of the exposure time, i.e. a speed of 1/500
> > second. Any given pixel will see 1/24 of the traverse time, i.e.
> > 1/500/24 = 1/12,000 sec.

>
> You're absolutely right. Not thinking each detail through. At that
> the slit is probably narrower than 1mm (@1/12,000) allowing an even
> slower travel time. This also slows down the spinning disk, which is a
> good thing! (Come to think of it I went through the same boo-boo
> routine here in a similar discussion a year or so ago... my neurons
> arem't cooperating).
>
> Cheers,
> Alan
>

theres a corollary to this effect as well. Although the per-pixel - or
per grain - exposure is 1/12000 sec, the total traverse time is quite
slow, about 1/500 or less, as you say. If you are photographing a
fast-moving object across the field of the camera, the object will have
moved some distance during the shutter traverse, so although the details
might be sharp, the image is time-shifted, causing vertical objects to
be slanted in the image. Back in the days of the 5x4 Speed Graphic and
similar cameras (with focal-plane shutter traverse time of about 1/20
sec), shots of racing cars would often show elliptical wheels and/or
leaning-over power poles, depending on how the photog panned the shot.

Cheers,

Colin D.

Alan Browne
Guest
Posts: n/a

 02-21-2006
Rich wrote:

> They could synchronize machine guns so they didn't blow
> the propellers off fighters in WW2, so making a multi slit camera
> mechanism should be simple.

The first synchonizers existed in WW I

Prior to that they had propellers with steel deflectors attached to
simply bounce the bullet away from the prop.

Alan Browne
Guest
Posts: n/a

 02-21-2006
Colin D wrote:

> theres a corollary to this effect as well. Although the per-pixel - or
> per grain - exposure is 1/12000 sec, the total traverse time is quite
> slow, about 1/500 or less, as you say. If you are photographing a
> fast-moving object across the field of the camera, the object will have
> moved some distance during the shutter traverse, so although the details
> might be sharp, the image is time-shifted, causing vertical objects to
> be slanted in the image. Back in the days of the 5x4 Speed Graphic and
> similar cameras (with focal-plane shutter traverse time of about 1/20
> sec), shots of racing cars would often show elliptical wheels and/or
> leaning-over power poles, depending on how the photog panned the shot.

Even at 1/200 a propeller will be "bent".

--
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David Littlewood
Guest
Posts: n/a

 02-21-2006
In article <4PuKf.7537\$(E-Mail Removed)>, Alan Browne
<(E-Mail Removed)> writes
>Rich wrote:
>
>
>> They could synchronize machine guns so they didn't blow
>> the propellers off fighters in WW2, so making a multi slit camera
>> mechanism should be simple.

>
>
>The first synchonizers existed in WW I
>
>Prior to that they had propellers with steel deflectors attached to
>simply bounce the bullet away from the prop.

The British (and possibly US) air forces used a hydraulic interrupter
design* by a Romanian gentleman by the name of Constantinesco. He had to
wait until several years after the war to get any payment (a few tens of
thousands) from the UK government, which they then proceeded to tax. He
took a tax appeal to the House of Lords, and lost. I imagine he must
have lost most of the money in this process. Still, it beats the few
pence a day most British servicemen got at the time.

*The firing of the machine gun was synchronised by a hydraulic impulse
from the engine, synchronised so that it fired at the right time to miss
both blades. The design of an interrupter for a machine gun firing at
600rpm (i.e. 10 rounds a second) is however a good deal different from
designing a shutter for a 10^-8 second exposure.

David
--
David Littlewood

Alan Browne
Guest
Posts: n/a

 02-22-2006
Kennedy McEwen wrote:

> In article <Y91Kf.467\$(E-Mail Removed)>, Alan Browne
> <(E-Mail Removed)> writes
>
>>
>> My Maxxum 9 has a mechanical shutter speed of 1/12,000 of a second.
>> Only 83 times slower than 1/1,000,000. It is a moving slit of the
>> curtains in the camera.
>>

> But the slit takes about 1/250th sec to traverse the entire frame. The
> fireball would be out by the time the first exposure was complete!
> Similar problem with the idea of the slit in a rotating disk, although
> with a big enough disk the slit could be larger than the frame size.
>
> It isn't just the exposure time that has to occur in 1/millionth of a
> sec, it is the exposure of the entire frame.

Somebody else beat ya to it.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

Kennedy McEwen
Guest
Posts: n/a

 02-22-2006
In article <(E-Mail Removed)>, Rich
<(E-Mail Removed)> writes
>
>They could synchronize machine guns so they didn't blow
>the propellers off fighters in WW2, so making a multi slit camera
>mechanism should be simple.

Even flat out, WW1 & 2 propellors moved many orders of magnitude slower
than atomic fireballs.
--
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
Guest
Posts: n/a

 02-22-2006
In article <deOKf.51523\$(E-Mail Removed)>, Alan Browne
<(E-Mail Removed)> writes
>Kennedy McEwen wrote:
>
>> In article <Y91Kf.467\$(E-Mail Removed)>, Alan Browne
>><(E-Mail Removed)> writes
>>
>>>
>>> My Maxxum 9 has a mechanical shutter speed of 1/12,000 of a second.
>>>Only 83 times slower than 1/1,000,000. It is a moving slit of the
>>>curtains in the camera.
>>>

>> But the slit takes about 1/250th sec to traverse the entire frame.
>>The fireball would be out by the time the first exposure was
>>complete!
>> Similar problem with the idea of the slit in a rotating disk,
>>although with a big enough disk the slit could be larger than the
>>frame size.
>> It isn't just the exposure time that has to occur in 1/millionth of
>>a sec, it is the exposure of the entire frame.

>
>Somebody else beat ya to it.
>

It happens. As do propagation delays getting posts from one server to
another. From what I can see, the above post was made at least 2hrs
--
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)