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Re: [OM] A shutter speed mystery

Subject: Re: [OM] A shutter speed mystery
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Mon, 12 Mar 2012 15:55:28 -0400
And there was plenty of "flash powder" in the guns!  :-)

Chuck Norcutt


On 3/12/2012 2:24 PM, John Ockman wrote:
> Very slow film, electrical sync. and lots of flash powder is my guess.
>
>
> On Sat, Mar 10, 2012 at 4:52 PM, Chuck Norcutt<
> chucknorcutt@xxxxxxxxxxxxxxxx>  wrote:
>
>> To my mild surprise the guns were fired electrically.  Perhaps it was
>> possible to synch the camera with the firing signal.
>>
>> Chuck Norcutt
>>
>>
>> On 3/10/2012 2:32 PM, Rick Beckrich wrote:
>>> .
>>>
>>> Agree with Mark... I once spent half a day at the Yakima Firing Range
>>> trying to
>>>
>>> capture the flight of the round from an 81mm mortar. Got lots of misses.
>>>
>>> .
>>>
>>>
>>>
>>> On Sat, Mar 10, 2012 at 11:46 AM, Mark Marr-Lyon<mark.marrlyon@xxxxxxxxx
>>> wrote:
>>>
>>>> It's possible that the guns there only ever fired dummy rounds for
>>>> practice, so the docent might not have been completely wrong :)
>>>> Certainly in wartime, explosive rounds would have been used.
>>>>
>>>> As for the photo, it looks like Speed Graphics were available in the
>>>> 1910s which had a 1/1000 s focal plane shutter. Presumably, fast
>>>> enough film also existed to use it. At that shutter speed, the
>>>> projectile only moves a foot, and since they're about 4 feet long, 3
>>>> feet of the blurred projectile would have been exposed for the entire
>>>> shutter duration (not accounting for focal plane shutter oddities,
>>>> which could probably be used to advantage), and easily visible in the
>>>> photo. The blur at 1/250 s should be pretty noticeable, and the
>>>> projectile would look ghostly. If the muzzle flash is providing the
>>>> light, then the background of the image would be dark. It's hard to
>>>> say more without seeing the photo.
>>>>
>>>> I've spent a bit of my professional life trying to take photos of
>>>> projectiles, and even trying hard to synchronize events it can still
>>>> take a fair amount of luck.
>>>>
>>>> Mark
>>>>
>>>> On Sat, Mar 10, 2012 at 8:12 AM, Johnny Johnson<theronemmie@xxxxxxxxx>
>>>> wrote:
>>>>> Thanks Chuck, it seems that our docent that day was less than well
>>>> informed
>>>>> and that some of the projectiles did include explosive charges. Also,
>> the
>>>>> maximum projectile weight was ~1/2 ton, not 3/4 ton. Now I wonder what
>>>>> other misinformation we were given. Oh well, at least we didn't pay for
>>>> the
>>>>> service.  :-)
>>>>>
>>>>> Cya,
>>>>> Johnny
>>>>>
>>>>> ---------------------
>>>>> Johnny Johnson
>>>>> Cleveland, GA
>>>>> On Mar 10, 2012 9:57 AM, "Chuck Norcutt"<chucknorcutt@xxxxxxxxxxxxxxxx
>>>
>>>>> wrote:
>>>>>
>>>>>> For those of you so inclined here is the entire 136 page "user's
>> manual"
>>>>>> for the 12-inch Mortar Model 1890MI.
>>>>>> <
>>>>>>
>>>>
>> http://www.scribd.com/doc/17375868/TM-9456-12inch-Seacoast-Materiel-12inch-Mortar-M1890MI-Mounted-on-12inch-Mortar-Carriage-M1896MI-and-M1896MII
>>>>>>>
>>>>>> All of the info about the various forms of ammunition is found on
>> pages
>>>>>> 77-101 (according to the index)  :-)
>>>>>>
>>>>>> Chuck Norcutt
>>>>>>
>>>>>>
>>>>>> On 3/10/2012 8:52 AM, Johnny Johnson wrote:
>>>>>>> Don't know the answer to your question Chuck but when I was there I
>>>> was
>>>>>>> impressed by the sheer size of the projectiles and the range. If I
>>>>>> remember
>>>>>>> correctly they were on the order of 3/4 ton each and had a range of
>>>> seven
>>>>>>> miles with a maximum altitude of ~three miles. They didn't contain
>>>>>>> explosives, just depended on the weight of the projectile to do the
>>>>>> damage.
>>>>>>>
>>>>>>> I do remember seeing the photograph that has you puzzled.  My only
>>>>>> reaction
>>>>>>> was to think of how neat it was that they caught the projectile on
>>>> film,
>>>>>>> not the technicalities of how it was done.
>>>>>>>
>>>>>>> Cya,
>>>>>>> Johnny
>>>>>>>
>>>>>>> ---------------------
>>>>>>> Johnny Johnson
>>>>>>> Cleveland, GA
>>>>>>> On Mar 10, 2012 8:00 AM, "Chuck Norcutt"<
>>>> chucknorcutt@xxxxxxxxxxxxxxxx>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> As a possible answer to my own question it occurred to me that the
>>>>>>>> projectiles (at only about 1/300 second after firing) are probably
>>>> being
>>>>>>>> illuminated by the bright flash of the guns.  So the film was
>>>> probably
>>>>>>>> exposed by the flash of the guns and not the ambient light.  Sort of
>>>> a
>>>>>>>> built-in strobe and not requiring a fast shutter or fast film.
>>   Sound
>>>>>>>> reasonable?
>>>>>>>>
>>>>>>>> Chuck Norcutt
>>>>>>>>
>>>>>>>>
>>>>>>>> On 3/10/2012 7:34 AM, Chuck Norcutt wrote:
>>>>>>>>> Yesterday we went with some friends to Fort DeSoto Park for a
>> picnic
>>>>>> and
>>>>>>>>> a bit of beach lounging.<http://en.wikipedia.org/wiki/Fort_Desoto>
>>>>>>>>>
>>>>>>>>> While a very large public park today, Fort DeSoto was originally
>>>>>>>>> constructed between 1898-1906 as a coastal defense battery to
>>>> protect
>>>>>>>>> Tampa Bay.  If you scroll to the bottom of the page linked above
>>>> you'll
>>>>>>>>> see some of the artillery and mortars originally installed here and
>>>> at
>>>>>>>>> Fort Dade a short distance away.  With 12" bores the mortars are
>>>> rather
>>>>>>>>> impressive beasts.  They were first fired in 1903 and were
>>>> deactivated
>>>>>>>>> not later than 1917.
>>>>>>>>>
>>>>>>>>> In a long corridor of historic photographs of the guns and
>>>> emplacements
>>>>>>>>> there is one very faded shot of two mortars being fired at the same
>>>>>>>>> time.  Much to my amazement the projectiles of both guns are
>> clearly
>>>>>>>>> visible perhaps some 30 feet above the muzzles.  According to the
>>>>>>>>> details I've been able to find about these guns the muzzle velocity
>>>>>>>>> ranges from about 1,000 to 1,500 feet/second depending on the
>>>> weight of
>>>>>>>>> the projectiles whose length ranges from about 3-4 feet.
>>>>>>>>>
>>>>>>>>> Now the shutter speed mystery.  How was this photo taken?  At 1/500
>>>>>>>>> second the projectiles moving at 1,000 feet/second move 2 feet or 4
>>>>>> feet
>>>>>>>>> at 1/250 second.  The angle of view from the camera's position
>>>> probably
>>>>>>>>> creates some foreshortening of the projectiles but it *appears* to
>>>> me
>>>>>>>>> that the shutter speed would have been not longer than 1/250.  I
>>>> don't
>>>>>>>>> know whether shutters of the period operated that fast but, even if
>>>>>> they
>>>>>>>>> did, I don't know how it would have been captured on a film
>>>> emulsion of
>>>>>>>>> the time.
>>>>>>>>>
>>>>>>>>> So, how was this photo taken?
>>>>>>>>>
>>>>>>>>> Chuck Norcutt
>>>>>>>>>
>>>>>>>> --
>>>>>>>> _________________________________________________________________
>>>>>>>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>>>>>>>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>>>>>>>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>>>>>>>
>>>>>>>>
>>>>>> --
>>>>>> _________________________________________________________________
>>>>>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>>>>>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>>>>>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>>>>>
>>>>>>
>>>>> --
>>>>> _________________________________________________________________
>>>>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>>>>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>>>>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>>>>
>>>> --
>>>> _________________________________________________________________
>>>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>>>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>>>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>>>
>>>>
>> --
>> _________________________________________________________________
>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>
>>
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