X-Git-Url: http://git.kpe.io/?a=blobdiff_plain;f=fov.lisp;fp=fov.lisp;h=a66d551f5cc87f0b1f342d8801903171ff89bbf2;hb=3dcc204b2a191c22f760f2c4caeb71e3802e3b80;hp=6fec649da285882846259180f3037c6fdaf74cd6;hpb=8910ad89a31d63e822079b060e4e2903c455fa75;p=cl-photo.git

diff --git a/fov.lisp b/fov.lisp
index 6fec649..a66d551 100644
--- a/fov.lisp
+++ b/fov.lisp
@@ -209,13 +209,29 @@ Returns: focal-length object-distance image-distance magnification bellows-facto
   (1+ (magnification :focal-length focal-length :object-distance object-distance)))
 
 (defun extension-tube (focal-length &key original-object-distance new-object-distance original-image-distance
-					 new-object-distnace original-magnification new-magification
+					 original-magnification
+					 new-object-distance new-image-distance new-magnification
 					 extension-length (units :feet))
   "Computes the parameters for using extension tubes.
 Requires: 1. original-object-distance, original-image-distance, or original-magnification
           2. new-object-distance, new-image-distance, new-magnification, or extension-length
-Returns: original-object-distance, original-image-distance, original-magnification,
+Returns: original-object-distance, original-image-distance, original-magnification, original-bellows-factor
          new-object-distance, new-image-distance, new-magnification, extension-length."
-  )
+  
+  (multiple-value-bind (focal-length o-od o-id o-m o-bf)
+      (close-up :focal-length focal-length :object-distance original-object-distance
+		:image-distance original-image-distance :magnification original-magnification :units units)
+    
+    (cond
+     (extension-length
+      (multiple-value-bind (focal-length n-od n-id n-m n-bf)
+	  (close-up :focal-length focal-length :image-distance (+ o-id extension-length) :units units)
+	(values o-od o-id o-m o-bf n-od n-id n-m n-bf extension-length)))
+     ((not extension-length)
+      (multiple-value-bind (focal-length n-od n-id n-m n-bf)
+	  (close-up :focal-length focal-length :object-distance new-object-distance
+		    :image-distance new-image-distance :magnification new-magnification :units units)
+	(values o-od o-id o-m o-bf n-od n-id n-m n-bf (- n-id o-id)))))))
+