I find photographing loose gemstones buy online to be an art form I may never fully conquer but I wanted to share a few tips I’ve learned over the years. My goal is not really to create an artistic photo of the gem but rather to depict the gemstone in the most accurate way. Lighting is by far more important than your camera setup but a few features on your camera are essential. A camera with manual mode that allows you to choose a custom white balance in Kelvin is a must as well as a good macro lens. I prefer using a focal length of 105mm macro lens so that I’m far enough from the gemstone to use my lighting setup. With this lens you can get about 6-8 inches away from the gem allowing for some flexibility.
I use two different lighting setups depending on what type of stone I’m shooting. I like to use the LED ring light from Table Top Studio for some gems and usually white balance around 6700K give or take. Even with proper white balancing though the LED lights will overemphasize the blue in gemstones. The LED setup works pretty well for green emeralds though. I also use a light tent with a couple daylight fluorescent bulbs that I white balance at around 5600K. For faceted gemstones I use a light on each side of the tent but if I’m shooting cabochons I use only one.
One mistake is to try to shoot gemstones pictures at your highest aperture setting. Often a really high depth of field will bring out too many details from the back of the gem and make it look much worse than with your naked eye. Try experimenting with a lower f-stop like f-11 or f-8 and see how it looks.