Hopefully you designed your x-ray machine to have an adjustable kilovolts-Peak. By doing so, you're able to adjust the image contrast. Higher voltages would mean higher x-ray eneries, and thus deeper penetration. The best way to describe this would be to show a few images...
[Image 1] is a radiograph of a steel gauge, set to a proper kVp for the job. Notice that all of the gauges are visible, albiet with the lighter ones a bit hard to see.
[Image 2] shows the same gauge, but at a higher kVp. The lighter gauges are now all but invisible...
[Image 3] shows the same gauge yet again, but this time at a lower kVp. Now everything is too dark.
[Image 4] is a flower imaged at about 28kVp. If we weren't able to adjust the kVp so low then the flower would be completely invisible! This is the benefit of building your own x-ray machine instead of buying one; you can adjust the kVp to whatever you want, not just from the usual 50 to 75kVp a dentistry machine will provide.
[Radiographs courtesy of Leslie Wright