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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