This was just brushed with light against a black backdrop. The f/22 did soften the image a bit, but did give a 4 inch DOF to keep the entire Lily in focus, which was my intent. Canon 50D w/24-70mm f/2.8L on a tripod.
Here is the technique I used for this image;
Install a tapered snoot to your flashlight with about a 1/4" diameter opening, (the size of a wooden pencil). I used black art paper and some gaffers tape, but any tape will do so long as it is not reflective. My finished snoot was about 5" long. You want it small enough so as not to spill light on too large of a surface at any time so adjust the opening to your liking. You can control the diameter of light hitting your area somewhat by moving your light in and out during exposure. I use a 7 LED flashlight, about 1 1/2" in diameter, that seems to give me enough light but not too much. Plus the bluish color provides a softer light than your standard bulb flashlight.
I chose to keep the ISO low in order to give me more time to brush the light just where I wanted it to go. For example, the light on the front of the Lily was a count of 20 seconds and the count on the inside was 45 seconds. I count because if I need more or less light I want to know what that means in time. On the front I slowly moved the light back and forth across and around the opening making sure I did not spill any light to the rim. For the inside I made sure that as I painting the light I lit all around the inside to eliminate any shadowing and create that hot spotlight look. Again making sure I kept the light from spilling too far out. You don't want to stop too long at any time as that will make a hot spot, or an uneven bright spot. Keep the light moving all the time, even if it is just very slow. If you want a very bright spot stop and use a circular motion to your desire and don't forget to count. A circular motion will cause the light edges to blur or blend keeping your image from that spotlight look.
The shutter speed is irrelevant to a point. Use as much shutter time as you need but don't over do it. Too long of shutter in total darkness will cause hot pixels, meaning you will start seeing red, green and blue specks, balance the time you need with your ISO to optimize your exposure time. I find that much over 2 1/2 minutes and hot pixels will start showing up in your black areas. The higher your ISO with long exposures the greater your chances of getting hot pixels in the dark areas of your image. One thing to keep in mind is that as you increase your ISO (your sensors sensitivity to light) the less time you will have on a given area of your subject. A few hot pixels can be cloned out, and I find that acceptable as long as they stay away from the dark areas of my subject. This particular image did not have any hot pixels, but the prior one of the bird of paradise had about a dozen red and blue specks.
And don't forget to turn out the lights!
Tools you need;
Remote shutter release that can be locked open, or on a long cord.
LED flashlight, 7-10 bulbs
Black art paper, not too thick, to hard to roll
Black backdrop, I say that because if there is anything behind the subject that is reflective it may end up in your image
A room that can be pitch black, or at night
And, a lot of patience, the Lily took 14 tries, the Bird of Paradise took over 30 tries to get them the way I wanted