diff --git a/Image-formats.md b/Image-formats.md
index 4ecff9f..545e9a3 100644
--- a/Image-formats.md
+++ b/Image-formats.md
@@ -51,6 +51,8 @@ These formats are not generally useful enough to be put into the DirectXTex libr
 
 See [PPM / PGM / PBM image files](http://paulbourke.net/dataformats/ppm/) and [Unofficial PBM format for HDR images, PFM (Portable Float Map)](http://paulbourke.net/dataformats/pbmhdr/)
 
+> The original proposal for PFM states there are no 'comment lines' like in ``ppm``. That said some tools like to add comments unless you explicitly tell them to not add it.
+
 # TIFF (Tagged Image File Format)
 The ``TIF`` or ``TIFF`` file format is kind of meta-container that is often used for image files used in various compressed formats, as well as other application. The image uses of this file format are supported by a built-in WIC codec. See [Wikipedia](https://en.wikipedia.org/wiki/Tagged_Image_File_Format) for more details.