I have a Nikon d5100, lens 18-55 and 55-300. I am assuming I should use the 18-55. What would be the best setting to use for shooting a Christmas Cactus? I don't have any lighting equipment etc just the camera and lens at the moment. Any suggestions? I am still learning.
First, there is a classic photography challenge about vision and composition that works for beginners as well as veterans: choose an item (in this case, your cactus) and find 30 different ways to shoot it. Not 30 different looks via post processing. But 30 different perspectives and compositions. Shoot from different angles. Shoot in different light. Shoot with different depth of field so only the needles or buds are in focus and the rest is a colored blur. Shoot at 18mm and distort the lines of the cactus. Shoot at f11 or f22 and have everything sharp and distinct. Shoot high key. Shoot low key. Yes, you can get advice from the rest of us. But conduct your own little experiment and see what is pleasing to your eye.
Second, ultimately the best answer to your question is going to depend upon what type of picture you want to create. Me...I like to shoot with a narrow DoF. I'd probably just focus on a couple of needles and make the rest a blur, shooting with a 50mm set on f1.4. Or I might try to create a series of contrasting shapes...surround the cactus with hard lines (maybe a series of triangles like some metal or plastic angles that the cactus is in the middle of and than shoot from above).
Third, assuming that what you want is an attractive picture of the cactus, my advice would be:
--moderate the light. Find a good north-facing window. A cloudy or overcast day (as long as it's not dark from impending storm clouds) would be good. Or on a relatively bright day a window with a light curtain that will turn the light into a soft light. Then get a white card or piece of foam core and put it on the other side of the cactus (to provide some soft fill light on the side away from the window). I'd shoot with a relatively small DoF (probably an f2 if any of your lens are that fast). I'd declutter the environment and probably surround the cactus with white or light colored items (maybe put it on a white sheet or placemat). Maybe put some color in the background that hints at the holidays without pulling the viewer's eyes away from the cactus. Which lens I'd use would be driven mostly by which one has the narrowest DoF (probably the 18-55). I'd set to ISO 100 or 200 and adjust upward only if I needed to b/c of shutter speed. I'd shoot auto aperture.