The second release button push before the second keep open the shutter until your finger on. It was nice for night picture or low light in a room.
I remember what said my father when he was police inspector in crime branch (before to go to a special branch to "return" Russian spy's, work sometime with US and U-K secret service too).
He explained to me when a crime in a room need a 2D shoot he closed the window, put shutter open with use of a very low speed film, go to the bar one hour... and scientist police moving around the body was not on the picture, only immobile subject was on. Apparently it is impossible to do now with digital !
My father (dead 64 years old) making also 9,5 mm and 16 mm movies with special effect, comic's, draw motion, fiction... and he got several prices.
I keep his secret service 2D camera call a "Robot"... the front shutter  could be closed and a mirror come to permit a 90° shoot by a very small (invisible) lens on the corner of the camera body.
A springiness permit many successive shoot... could be good for stereo Cha-cha or lenticular shoot needed several frames. I never think to use it :-\

Jm

Le 24/02/2014 20:53, Duke a écrit :

 

The Hannel Tri-vision is certainly a classic...I didn't know it went all the way back to 1940!   Choice of stereo base was a nice feature.  It looks as if it has two shutter release buttons, why is that?

Duke

On Sun, Feb 23, 2014 at 6:07 PM, forum(-at-)trivision3d.com <forum(-at-)trivision3d.com> wrote:

 

TKS Duke. Notice the Hannel TRI-VISION 3D camera 1940 was first a three lenses to permit to choice stereobase, than second version was two lenses only.
But for economy they do not change the three red inactinic window behind.

Jm

Jm

Le 23/02/2014 22:10, Duke a écrit :

 

Excellent phantogram...very realistic!

Duke

On Sun, Feb 23, 2014 at 4:01 PM, forum(-at-)trivision3d.com <forum(-at-)trivision3d.com> wrote:

TKS Duke... here is the phantogram version I call Exoglyph.

Jm

--

3D info:  SPM, Photoshop.

My 3D anaglyphs on Flickr
http://www.flickr.com/photos/ddduke/sets/72157603868766664/