Firstly, not all cameras are good at capturing low level spectrum's... That said,
A key to capturing black objects well, is even controlled lighting.
You have to illuminate all sides of the object well enough, and the lighting
must be flat/even... so it will not create sharp contrast. A cameras un-diffused
flash for example, will create a bright high contrast area... and reduce the spectrum
of visible blacks captured.
Many such objects are photoed in a "light-tent". A small wire frame that has white
translucent bed-sheet type material mounted to it. They place the object in the tent,
and light all sides of the tent from far enough back to keep a spotlight effect from
occurring. The camera then may either not use a flash, or will have some sort of
light diffuser attached to it, which will spread the light out more, and keep it from
making bright hot-spots.
If the object is too light, one can always use photoshop to create contrast,
reducing the spectrums a bit. However, one can not take a bad photo which is
missing a wide range of spectrum, and make it look good with photoshop.
Turning up the brightness with missing spectrum will reveal the missing colors
that much worse.