Thanks, dainisjg.
The photos above used the camera's auto exposure, but the results varied
dramatically because of the ratio of dark and light in the scene. The remedy for those overexposed and underexposed images is the
EV or exposure compensation control. If the photos look too dark, set this control for a positive (e.g., +1.0) value. If they are too light, set the control for a negative (e.g., -1.0) value.
A simple tool which can help you get more accurate exposures is an
gray card. Such a card is printed to a precise and neutral value of 18% gray (white = 0% and complete black = 100%). Here's one in use on my ebay table...
With a basic digital camera, you can take a closeup photo of such a card with the camera on its auto exposure setting. That will give you a perfectly exposed shot for your particular lighting setup.
Even most basic digital cameras will then let you find out what combination of shutter speed and lens aperture was used for that image. That info isusually displayed when you review your picture.
You can then set the camera in its manual or semiautomatic mode for that same combination of shutter speed and aperture. After that,
every shot you take with the same lighting will be exposed exactly right.
Which leads us to that other very important tool for eBay photography, your lighting...