diff --git a/make-includes/standard_rules.make b/make-includes/standard_rules.make
index 86df9ab..73eaaa0 100755
--- a/make-includes/standard_rules.make
+++ b/make-includes/standard_rules.make
@@ -68,9 +68,19 @@
 #
 # PNG from TIFF (slide background)
 #
-%-BG.png: %.tif
+# We lighten these so that they don't overwhelm the text. Note that 15% is
+# too light for most data projectors, so let's try 33% and see what
+# happens... (this looks far too much on screen, but data projectors tend
+# to wash things out much, much more).
+#
+# Includes both blurred and unblurred versions, use as required.
+#
+%-BG.png: $(IMGDIR)/%.tif
+	convert $< -threshold "-1" -depth 16 - | composite -dissolve 33% $< - $(IMGDIR)/$@
+#
+%-BG-blur.png: %.tif
 	convert -blur 0.5 $< $(IMGDIR)/$*.png
-	convert $(IMGDIR)/$*.png -threshold 0,0 - | composite -dissolve 25% $(IMGDIR)/$*.png - $(IMGDIR)/$@
+	convert $(IMGDIR)/$*.png -threshold "-1" -depth 16 - | composite -dissolve 33% $(IMGDIR)/$*.png - $(IMGDIR)/$@
 #
 # PNG from PICT.
 #