Preachdude wrote:
Professional quality results means ideally putting the jewelry on velvet and lighting with a ringlight on a macro lens.
That is one solution, but only one of many, and not necessarily the most versatile, cheapest, or easy to use.
As many people have confirmed, lighting and backgrounds are critically important. Velvet can be good, but dust can be an issue if within the focus zone for dark or colored backgrounds.
Flash is much harder to use than consistent studio lamps. With flash of any kind you only see the results after the fact. With studio lights - which can be much cheaper - you can see the results while composing the image.
Ring flashes have limited use and are expensive. If you want directional light then they may not be the best approach even though some have some programmable capability to give some directional effect. They tend to be the most expensive of course, such as the Canon Ring flash Speedlites.
Then what do you do with models? They present a different challenge from a lighting perspective. As has been said, the accent needs to be on the jewelry, not the model - face, neck, hands, or whatever other part of the anatomy the jewelry is designed to enhance.
Then there is the question of what concept the photographs are supposed to convey. If it is creative work to stimulate demand - advertising, glamorous, a sense of lifestyle - then atmosphere becomes important.
However, there will usually also be a need for accurate, descriptive photographs so that potential customers can get a very clear impression of what they are buying. The more expensive the product, the more important that becomes.
I would suggest that researching the catalogs of some of the major auction houses - Christie's, Sotheby's, Bonhams - would be time well spent, since they have to document both desire for the item and authentic representation.
http://www.bonhams.com/departments/JWL/?keep_login_open=1Other than the lighting, I think you already have most of the equipment that you need, except for the possibility of some inexpensive extension tubes.
A few hundred dollars on lighting - say $200 to $400 - would give you a very versatile capability beyond this project, and that is far less than a macro lens and a ring flash.
However, there are many approaches to this project, and only you can choose which is best suited to your needs.