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Re: [OM] A shutter speed mystery

Subject: Re: [OM] A shutter speed mystery
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sat, 10 Mar 2012 16:48:37 -0500
If I get back there (but not likely this year) I'll try to take a shot 
of the photo.  It's not in good shape.

Chuck Norcutt


On 3/10/2012 11:46 AM, Mark Marr-Lyon 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
>>>>>>
>>>>> --
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>>>>>
>>>>>
>>> --
>>> _________________________________________________________________
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>>>
>> --
>> _________________________________________________________________
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>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>
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