film speed..... circa 1945

[CMoore]

Just for example -
WW2, January 1944, flying photo reconnaissance, in a stripped-down Spitfire or Mosquito.
Their ground speed, depending on altitude of anywhere between 300 and 25k feet, was probably 325-425 MPH.?

How did they get those photos.?
What type of film and ASA was available to them, and what shutter speeds would they have been using.?

Thank You

BTW, how many of you could spell reconnaissance.?
I missed it by an N, A and S

 

[AgX]

Shutter speed in aerial photograophy is depending on image speed. And this again is dependand on image scale.

Morevover the taking angle is of influence too. In military reconnaissance it was not only photographed vertically but also as high-oplique forwards. Then you have image expansion instead of image lateral movement. But still the effect is lesser as in vertical taking at same scale.


vertical taking:

Image Speed = Ground speed x Image Scale

 

[Ian Grant]

During WWII in 1941Ilford introduced HP3 a 400 ASA/BS emulsion to replace HP2 which had been released in 1937, at the time it had a nominal ASA of 125 however the ASA system was revised in 1955 raising the speed to 250 and that was revised again in 1960 to 400ASA. There was no actual change in the film emulsion itself just a change in how films were exposed, better exposure determination allowed safety margins to be cut significantly. I used HP3 in the late 1960's and it was an excellent film as was FP3.

Kodak Tri-X the equivalent of HP2 has been released in 1938/9 as a sheet film but production ceased before the introduction of 35mm and 120, this was almost certainly because a key component had come from Germany. Tri-X technology would have fallen into German hands when they invaded Hungary and placed Kodak Ltd's Hungarian coating facility under Agfa's control. Kodak's fastest film was then Supper-XX Aero. There's not a listed speed in my catalogue but normal Super-XX had a nominal speed of 31º Scheiner (European) around 80 ASA (around 200 ISO by todays standard).

Ian

 

[AgX]

There's not a listed speed in my catalogue but normal Super-XX had a nominal speed of 31º Scheiner (European) around 80 ASA (around 200 ISO by todays standard).

31° Scheiner `=` 21° DIN (from 1934) = 24° DIN (from 1961) = 200 ISO