Upon uploading the sphere, I see that the terminator shadow is too far back.
3rd grey scale attempt. Tried using GIMP to tone down incandescent light temperature. I ordered a couple of Strathmore Toned Grey 5.5in x 8.5in sketchbooks. Looks like I need to get outside, during daylight, to get better results with snapshots.
Using cardboard in lieu of Strathmore Toned Grey sketchbook
Five step grey scale on standard Strathmore sketchpad - 5.5" x 8.5"
Compared to the above, just posted, this looks like grey toned background.