Logiteck Quickcam Chat resolution

I have a Logitech Quickcam Chat (046d:092c).  I was pleased to find that 
is was supported (by gspcav1) by Ubuntu 8.04 out of the box.  (Not so for 
Fedora 9 -- they avoid out of tree drivers, as we know.)

To test the camera, I did an "acquire" under the GIMP.  This invoked 
xsane which in turn used the v4l library or API.

The only resolution that xsane offered me was 160x120, either 8-bit 
grey-scale or 24-bit colour.  When I look at the specs for this camera, I 
see 

According to the specifications here: 
  http://www.logitech.com/index.cfm/38/281&cl=us,en
I think that the resolution ought to be 352x288 or perhaps 320x240.  The 
640x480 resolution appears to involve interpolation.

Why am I only offered 160x120?  Is that a camera issue, a gspcav1 issue, a 
v4l issue, an xsane issue, a GIMP issue, or an ignorant user issue?

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