--- ray/doc/man/man1/pdfblur.1	2003/03/11 19:20:21	1.1
+++ ray/doc/man/man1/pdfblur.1	2005/01/18 20:19:56	1.5
@@ -1,11 +1,10 @@
-.\" RCSid "$Id"
+.\" RCSid "$Id: pdfblur.1,v 1.5 2005/01/18 20:19:56 greg Exp $"
 .TH PDFBLUR 1 1/24/96 RADIANCE
 .SH NAME
 pdfblur - generate views for depth-of-field blurring
 .SH SYNOPSIS
 .B pdfblur
 .B aperture
-.B distance
 .B nsamp
 .B viewfile
 .SH DESCRIPTION
@@ -14,11 +13,11 @@ takes the given
 .I viewfile
 and computes
 .I nsamp
-views based on a focus distance of
-.I distance
-and an aperture diameter of
+views based on an aperture diameter of
 .I aperture
-(both in world coordinate units).
+(in world coordinate units) and a focal distance equal to the length of the
+.I \-vd
+view direction vector.
 When rendered and averaged together, these views will result in
 a picture with the specified depth of field.
 Either
@@ -87,6 +86,29 @@ We have found a
 .I nsamp
 setting somewhere between 5 and 10 to be adequate for most images.
 Relatively larger values are appropriate for larger aperatures.
+.PP
+The
+.I \-pd
+option of
+.I rpict
+may be used instead or in combination with or instead of
+.I pdfblur
+to blur depth-of-field.
+If used in combination,
+it is best to set the
+.I \-pd
+option to the overall
+.I aperture
+divided by
+.I nsamp
+to minimize ghosting in the output.
+.PP
+To simulate a particular camera's aperture, divide the focal length of
+the lens by the f-number, then convert to the corresponding
+world coordinate units.
+For example, if you wish to simulate a 50mm lens at f/2.0 in
+a scene modeled in meters, then you divide 50mm by 2.0 to get 25mm,
+which corresponds to an effective aperture of 0.025 meters.
 .SH EXAMPLES
 To use
 .I pinterp
@@ -112,4 +134,4 @@ Greg Ward
 .SH BUGS
 This program really only works with perspective views.
 .SH "SEE ALSO"
-pcomb(1), pinterp(1), pmblur(1), rcalc(1), rpict(1), vwright(1)
+pcomb(1), pinterp(1), pmblur(1), pmdblur(1), rcalc(1), rpict(1), vwright(1)