I don't know what kind of setup your girlfriend has for taking photos of jewelry, but she should also have a good light box/tent. A good light box/tent. Depending on the type of jewelry, she might need different macro lenses. For instance, rings or ear rings/studs might do better with a longer focal length, while broaches or necklaces might work better with a shorter focal length. The Tamron 90mm f/2.8 might be a good choice for smaller pieces, but the Nikon 40mm f/2.8 that socalbirdman mentioned might be good for larger items.
- The lens is the thing.
- 'Full Frame' is the new 'Medium Format'.
- "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.