X-Git-Url: http://git.kpe.io/?a=blobdiff_plain;f=fov.lisp;h=64bbe80c737aaa71ffce0b2618ec9c7bfae71ae5;hb=50e13cbf899629662bacf8e224b4daeaabc2b054;hp=211820af13e616d9d5b83818b908f84e47eb8a15;hpb=cd49c092c9ede840170af3301b9296cec4b0be3e;p=cl-photo.git

diff --git a/fov.lisp b/fov.lisp
index 211820a..64bbe80 100644
--- a/fov.lisp
+++ b/fov.lisp
@@ -159,7 +159,7 @@ focal-length and image-distance are in mm, object-distance is in units"
    (t
     (error "Must set two, and only two, of the parameters: image-distance, object-distance, and focal-length."))))
 
-(defun close-up (&key focal-length object-distance image-distance magnification (units :feet) &aux bellows-factor)
+(defun close-up (&key focal-length object-distance image-distance magnification (units :feet))
   "Computes the parameters for focusing closer than infinity.
 Requires two, and only two, of the input parameters.
 Returns: focal-length object-distance image-distance magnification bellows-factor."
@@ -208,3 +208,54 @@ Returns: focal-length object-distance image-distance magnification bellows-facto
   "Returns the bellows factor, the ratio of effective aperature to actual aperture."
   (1+ (magnification :focal-length focal-length :object-distance object-distance)))
 
+(defun n-args-not-nil (n &rest args)
+  "Returns T when count N of input args are not nil."
+  (= n (count-if-not #'null args)))
+
+(defun extension-tube (focal-length &key original-object-distance 
+		       original-image-distance 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, original-bellows-factor
+         new-object-distance, new-image-distance, new-magnification, extension-length."
+  
+  (when (or (not focal-length) (not units)
+	    (not (n-args-not-nil 1 original-object-distance 
+				 original-image-distance
+				 original-magnification))
+	    (not (n-args-not-nil 1 new-object-distance 
+				 new-image-distance
+				 new-magnification
+				 extension-length)))
+    (error "Invalid arguments.
+Must set 1 of the following original-object-distance, original-image-distance,
+or original-magnification parameters as well as one of the following parameters
+new-object-distance, new-image-distance, new-magnification, or extension-length."))
+
+  (flet ((ret (ood oid om obf nod nid nm nbf e)
+	   (list :focal-length focal-length :original-object-distance ood
+		 :original-image-distance oid :original-magnification om
+		 :original-bellows-factor obf :new-object-distance nod
+		 :new-image-distance nid :new-magnification nm
+		 :new-bellows-factor nbf :extension-length e)))
+
+  (multiple-value-bind (focal-length-original 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)
+    (declare (ignore focal-length-original))
+    
+    (cond
+     (extension-length
+      (multiple-value-bind (focal-length-new n-od n-id n-m n-bf)
+	  (close-up :focal-length focal-length :image-distance (+ o-id extension-length) :units units)
+	(declare (ignore focal-length-new))
+	(ret 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-new 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)
+	(declare (ignore focal-length-new))
+	(ret o-od o-id o-m o-bf n-od n-id n-m n-bf (- n-id o-id))))))))