Declaration error on root level when applying namespace prefix

[rbutler]

I get a constant 'Declaration' error when using namespace prefix and validating the xml file. Tried it with netbeans

Cannot find the declaration of element 'c:camera'

and xmllint

element camera: Schemas validity error : Element '{http://www.camera.org}camera': No matching global declaration available for the validation root.

. I think I didn't understand the concept. But on the other hand this is an example out of the Internet and is similar to many other examples out there.

camera.xml [pastebin.com ]:

<?xml version="1.0"?>
<c:camera xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:c="http://www.camera.org"
 xsi:schemaLocation=". camera.xsd">
 <c:body>
 <c:description>
 Ergonomically designed casing for easy handling
 </c:description>
 </c:body>
 <c:lens>
 <c:zoom>300mm</c:zoom>
 <c:f-stop>1.2</c:f-stop>
 </c:lens>
 <c:manual_adapter>
 <c:speed>1/10,000 sec to 100 sec</c:speed>
 </c:manual_adapter>
</c:camera>

camera.xsd [pastebin.com ]:

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
 <xsd:element name="camera">
 <xsd:complexType>
 <xsd:sequence>
 <xsd:element name="body"/>
 <xsd:element name="lens"/>
 <xsd:element name="manual_adapter"/>
 </xsd:sequence>
 </xsd:complexType>
 </xsd:element>
</xsd:schema>

I understand that in this case namespace prefix is not required but I want to understand why it is not working.

Your help is very much appreciated!

Thanks,
Ralf