Add x-y adjustment section

NOTES_ON_OPTICAL_PRINTER_TECHNIQUE.md

@@ -193,3 +193,36 @@ At indicated f/5.6 there is already more than enough depth of field for a bipack
 Also it is unnecessary to refocus when adding the second film.
 Likewise when a single film is reversed emulsion to base.
 At larger apertures and at larger magnifications depth of field is less.
+
+## BOLEX PRISM 
+
+It isn't a worry.
+There isn't a distinction between RX lenses and non-RX lenses for most any lens which will be used on a bellows for optical printing.
+
+## BOLEX GROUNDGLASS
+
+Only for the best optical printer lenses, which will be used at apertures larger than f/4, does the Bolex groundglass need to be reset from its everyday position.
+
+## DEFOCUS
+
+To throw an image out of focus without changing its size, if printing at 1:1, move the camera a distance and the lens 1/2 this distance, in the same direction.
+
+## X-Y ADJUSTMENT
+
+Besides its to and fro movement the lens has lateral movements.
+These adjust the position of the original frame's image on the print frame.
+For example, if the lens is raised a bit...
+
+**![Graphic depicting a lens' central position between two frames demonstrating a rise adjusting framing](#)**
+
+At 1:1 moving the lens up a distance d raises the viewed field by twice d.
+Likewise for down, right, and left.
+
+At `M > 1` lateral adjustment effects a scan of the original frame.
+This is not geometrically equivalent to a pan, bad it been made in the original photography.
+
+On simple optical printers the only lateral adjustment is of the lens (rather than the heavier camera or gate).
+This is geometrically adequate.
+
+But the J-K adjustments are even too flimsy for a lens.
+It helps, after they are set, to gently tap the lens, so it finds a stable position, and then to readjust if necessary, etc., etc.