[Image-SIG] Tiff not reading dpi

[Dennis Shimer]

I have a tif image that at least 3 different programs can see the
correct dpi information in
(Irfanview, Gimp, Alchemy) but when I read the image using pil 1.6

print im.info  -  shows only {'compression': 'raw'}
dpix,dpiy=im.info['dpi']  -  gives an exception

and if I set it explicitely then using
im.save(filename,dpi=(dpix,dpiy))

Irfanview sees the new dpi.
Gimp complains that "resoultion units are meaningless"
and Alchemy sees no DPI info at all but doesn't complain.

Is there any reason that there is so much inconsistancy in results, or
a way to write dpi with pil that would be universally recognized?