Nice continuing thread about knife images. Many of my knives were photographed with natural "window" light but unfortunately, none are of a "northlight" variety. The reason for using "northlight" is because the sun is never in the north in our hemisphere and so soft indirect light is always available.
With natural light, time of day can have an effect upon the image due to the change in color temperature of light and of course ones time for photographing is based upon the daylight hours and as Coop has said, he often is only available when there is no "available natural light".
What I do is to use a light tent to prevent color affecting the blade and with daylight flourescents, allow me to use cool, soft, diffused indirect continuous lighting at anytime of day.
when I first created the setup, I did this Schuyler Lovestrand Subhilt Fighter with the setup using Natural "Window" Light thru patio doors and then with the Daylight Flourescents lights (4 15 W=50W). Both images are essentially the same and are straight from the camera with no image editing.
Phil has a small image on one of his posts showing the current setup which I and Roger P use. I use a Nikon 995 and he uses the CP Nikon 5000. We do use a tripod as the exposures generally are about 1/4 sec at f 3.1. I prefer a background of a neutral "gray" tone which does not mean gray but a background that reflects light of that tone so that the auto exposure does not get unduly affected by the background. I'm a firm believer in the "kiss" principle.
While I don't have Coops and Phil's image editing skills, these are some of many similar images of knives that I own.