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The Great War in Stereoviews

Medium Format (6 x 13 cm) and Small Format (45 x 107 mm) Glass Stereoviews

Most manufacturers made their glass stereoviews available in both 6x13 and 45x107 formats.  While original medium format slides could be cropped into small format, the reverse was not true, so slides taken with a small format camera were only available in that format.

Converting  a medium format slide to small format was not done by a machine making the entire image smaller, but by cropping the medium format image. Since the two formats have different aspect ratios (6 x 13 cm—.46; 45x107 mm— .42), [1] relatively more cropping was necessary in the vertical dimension.  The example below illustrates this process. In order to make a small format version, 2.3 cm (18%) was cropped from the sides and 1.56 cm (26%) from the top and bottom.  As may be seen by the soldier in front of the bunker in the left image, cropping keeps the subjects of interest the same size in both formats.  A new title bar was usually made for small formats, since it was cropped with the image.

Medium Format LSU 2021: 1917 Entonnoir de mines aux Éparges (1917 Mine crater at Les Éparges)

Small format LSU 2021, published as SDV 577. 

Medium format view above cropped to match small format.

It is not merely a matter of size; a shot composed for a medium-format camera lacks many of the details after conversion to small format.  For distant landscapes such as the one above, the effect may be hardly noticeable, but close-ups are different in an artistic sense, as shown below.

LSU 2040 Le Mont-Haut 1918 Entrée d'un tunnel pris aux allemands (Mont Haut—Entrance to a tunnel taken from the Germans), 6 x 13 format (top) and SDV 355 (bottom).

The additional detail of the tunnel construction and the stereo effect of the ribs were largely lost after conversion to the smaller format of SDV 355. Note that the title bar is actually two bars; the left is the same on both views, while the right has been redone. The reversed "355" is typical of LSU/SDV views.

Horizontal and vertical cropping was not the only source of image loss when converting 6x13 images to 45x107.  The standard 45x107 camera and viewer had an approximately 20mm-wide dead space that blocked the center of the slide. The size of the center bar  in standard 45x107 slides varies from 15mm to 24 mm; the commercial Brentano’s slides typically have a clear center 18-20mm wide. Conversion from medium to small format often included creating clear bars on either side of the title bar so the slide would more closely resemble a slide taken with a 45x107 camera.  As shown in the LSU examples below, even without making clear bars the center could not be seen in a 45x107 viewer.

LSU 8422 Albert—La Basilique

Albert—The Basilica

 6x13 format (top) compared to the 45x107 version with clear bars (bottom).

LSU 9570 Peronne: Vue prise du Chateau

Peronne: View taken from the Chateau).

6x13 compared to 45x107 without clear bars; the 20mm area not visible through the viewer is shaded.

In summary, cropping and the larger obscured area in the center result in a 45x107 slide with only about half the viewable area of a 6x13 original.

·       Medium:    60 x 130 = 7800 mm2

                 minus   60 x     6 =   360 mm2 (title bar area)

                                               7440 mm2   Total viewable image area

·       Small:        45 x 107 = 4815 mm2

                minus   45 x   20 =   900 mm2 (title bar area)

                                                      3915 mm2   Total viewable image area (53% less)

NOTE: American Fisherview glass stereographs are in a nonstandard medium format. A Fisherview plate is slightly narrower and has a 12mm title area running its full width, so the viewing area is only 6050mm2, or about 81% that of a French medium format view.

[1] Slide measurements vary slightly.  A typical 45 x 107 is closer to 44 x 107, and a 6 x 13 can be 59-60 mm x 129-130 mm.  In addition, vertical and horizontal borders (i.e., distance from the edge of the image to the edge of the glass) typically vary from 0-3 mm (usually 0-1 mm) for 45 x 107, and 0-5 mm (usually 1-2 mm) for 6 x 13.

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