P3D Mounting stereo prints 2

[dale.walsh@xxxxxxxxxxxxxxx]

	Version 2 which I hope is better.


	Concerning questions asked about mounting stereo prints, I have taken the =
liberty of sending a few quotes from an excellent resource for 3D photograp=
hy which is available from the authors below.  If anyone is interested, I c=
ould get you the address.  Hope this helps.


Dale Walsh


A STEREO/PHOTO GLOSSARY



   by: Craig Daniels and Dale Hammerschmidt


 Scopeability:  A jargon term used in reference to a view's over-all ease o=
f being  viewed.


Standard separation of homologous points, suitable deviation, absence  of r=
otation, a well placed window, balanced printing, accurate image  alignment=
/masking/trimming --- all of these contribute to a good view. This is  some=
times spelled scopability,  but to describe  the difference as a point of  =
controversy would be overstatement.


 Interpupillary distance (IPD):  The distance between the pupils of the eye=
s when vision is at infinity.  IPDs range from 55 to 70 millimeters, but th=
e average is usually taken to be somewhere between 63.5 and 65 mm (2-1/2 in=
ches).


  Interocular distance:  The separation between optical centers of a viewer=
 (which may be adjustable). (From L. oculis, eye; an ocular lens is one thr=
ough which the eye views, as opposed to an objective lens. So the interocul=
ar distance is the distance between the optical axes of the eyes themselves=
, or of the ocular lenses of the viewer which should be the same). In stere=
ography, the term is usually used to refer to the distance between the axes=
 of the ocular lenses, which may not be quite the same as the distance betw=
een the axes of the eyes (for reasons of collimation q.v.). It is a common =
error to assume that the interocular distance should agree with the interpu=
pillary distance of the observer. It should be equal to or slightly greater=
 than the maximum separation of homologous  points of the view (in the case=
 of a simple viewer) or such points of the image formed by the objective le=
nses (stereoscopic optical viewing system).  See collimation.


Collimation: When the distance between the optical centers of a stereoscope=
 and the separation of the image pair placed in it are equal, and when the =
images (or view) are (is) placed at the full focal length, the lenses of th=
e stereoscope act agreeable as collimators  for the homologous points of th=
e image pair. This means that the interpupillary distance of any user's eye=
s is automatically accommodated without adjustment. It also means that one'=
s eyes need not be level with the view (a great convenience in viewing).  A=
ccordingly, gravity-leveled eyewear has been proposed for viewing side-by-s=
ide pairs presented on a fixed screen at close range.


Interpupillary distance (IPD):  The distance between the pupils of the eyes=
 when vision is at infinity.  IPDs range from 55 to 70 millimeters, but the=
 average is usually taken to be somewhere between 63.5 and 65 mm (2-1/2 inc=
hes).


A special case worth mentioning is the use of windows with arched tops. Bec=
ause the arches are in part vertical, they give distance information. There=
fore, if one uses the upper edge to align the homologous points in a print,=
 there is a great danger of error; homologous points should be the same dis=
tance below the top edge (of a curved top) only in the object is meant to b=
e in the plane of the window. This may be seen in the illustration below. T=
he caneweave patterned blob is in the plane of the window, and is identical=
ly positioned in each frame. The speckled blob is behind the window, and is=
 slightly further down from the top edge in the right-hand chip. But it's t=
he same distance up from the bottom of the image in each chip. It is best f=
or arched tops to make all measurements from the bottom, and with great car=
e.


Homologous distance:  The distance between two homologous points (meaning t=
he same, except for being the left and right versions) in a stereo view.  T=
he maximum separation of such points in a view's distant subject matter are=
 often said to be the separation of the view, and held to some standard.  T=
he optical centers of the lenses of a stereoscope (or free hand lorgnette) =
are separated by this distance or more.





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