A few thoughts that may or may not lead to further enlightenment:
I went to Jim Zuckerman’s page and there I see he has free e-magazine, which on the first page says he does not like photo contests. His reasoning is that you are shooting to please yourself, not some random person who happens to be judging a contest. This is certainly a good attitude. But, as I said, if you really want to know how others feel about your work, contests and critiques are more reliable than gallery comments. If you were to photograph professionally, every potential customer becomes a judge.
Looking at other photographer’s work and deciding what you like and don’t like about a photo will help you, as will trying to figure out how a photo was lit and shot.
I also went to Bryan Peterson’s page and the first image I saw was a little boy in a green shirt, looking out of the frame with his feet cut off at the ankle joint! It seems to me, I have read cropping at the joints is a bad practice, as is having your subject looking out of the frame instead of into it. The photo was also taken in fairly harsh light! It does follow the rule of thirds, and it has complimentary red and green colours. And, a cute subject. There are a couple of points worth noting. “The Rules” are just guidelines. Knowing them is important. Knowing you can break them and still get a good, sometimes an even better photo, is important too. The other point is that in nature and reportage, you are rarely in control of the scene. Your subjects do not take direction well, if at all. Take the photo you see, when you see it. If you have a chance, take more photos and try to improve on the first one, but get the first one because if you hesitate, you miss the shot completely and it is gone forever.
In Brian’s portfolio, shot 15 is someone in a blue coat and red hat, in front of what may be an abandoned factory. It is a strange departure from the rest of the gallery. In Jim’s e-magazine, which will probably be changed out for a new one shortly, there is a section on centering your subject which shows a white rhino centered and also using rule of thirds. The article makes a couple of good cases for putting your subject in the centre, but I don’t think Brian’s image benefits from it.
Light and shadow are what photography is all about. A good book is Light Science & Magic An Introduction to Photographic Lighting, Third Edition, by Fil Hunter, Steven Biver and Paul Fuqua, from Focal Press. The link is to an even newer version -> http://www.amazon.com/Light-Science-Magic-Introduction-Photographic/dp/0240812255/ref=sr_ob_2?ie=UTF8&qid=1356706473&sr=8-2
To a degree with close-up and to a greater degree with macro, manual focus is important because the camera’s focusing system is geared to general photography and when working with extremely thin depths of field, repositioning the camera usually results in loosing the desired focus. A tripod can be helpful. Some new macro lenses have exotic image stabilization which makes hand held macro photography much easier. Film SLR’s without computerization had focusing screens with micro-prisms to aid manual focusing. The new computerized cameras have a simple ground glass or plastic focusing screen because the manufacturer expects you to use auto-focus most of the time. Lenses designed for manual focus have more travel in the focusing ring, and a different feel when in use. The Canon 50 mm f/1.8 lens is a great example of a lens for which manual focus was not a design consideration. The focusing ring is barely there!
Using a camera is a bit like driving a car. You can get the car down the road if you understand the accelerator, break and steering, but you will enjoy the experience more if you understand the seatbelts, radio, air conditioning, sun roof and so on. The main camera controls are shutter speed, aperture, focusing and ISO, but there is so much more to most modern computer driven cameras. It is worth reading the manual periodically because what may have seemed unimportant when you got the camera may be useful now that you have more experience and perhaps more peripheral gear.
Full manual mode has its place. A studio environment is an example of that place. The camera knows nothing about studio strobes and has no way to talk to them. Manual mode keeps the camera from making assumptions about the light that will not be correct when the strobes fire. If you are using a speedlight set to manual mode, the same may apply. On the other hand, if you are setting the mode dial to M and then just adjusting until the meter is in the centre, there is usually not much benefit to using manual mode. Program mode, Aperture Priority and Shutter Priority all have their place. People who are using manual mode because it is “cool” or because it is how “pro’s” shoot, are working too hard. Frequently Aperture Priority, Shutter Priority or even Program mode are more appropriate choices.
Since you have a Nikon, you might enjoy books by Joe McNally. He shoots with Nikon and writes a lot about the Nikon flash system. Plus, he has great photos.
When shooting macro, and even close-up, if you have enough light, use a really small aperture to get more depth of field. Try f/22, f/32, or even smaller if your lens supports it. I have some thoughts and photos about macro photography here: http://cameraclicker.com/Compare/Macro/Macro.html, and some thoughts on depth of field, including macro, with more photos here: http://cameraclicker.com/Compare/DOF/DepthOfField.html. If you have a program like Photoshop, you can do focus stacking. You take a series of photos of the same subject either moving the camera slightly between each shot using focusing rails, or you keep the camera steady and adjust focus slightly each time. When you have completed the photo taking step, you have a set of photos, each with an in-focus piece of the subject. The set of photos is fed to the software which adjusts and combines the photos to give a final image that contains the sharpest parts of all photos to show your whole subject in focus. For it to work you need a subject that is not moving, but when it works, it gives amazing results.
Post processing is important, for all your images. People posting in many of the forums seem to have this obsession about posting straight out of the camera. A problem with that is most digital cameras have a low pass filter over the sensor. There are a few exceptions like the Leica M bodies and Nikon’s D800e (the more expensive of Nikon’s D800 bodies has one less part!). The low pass filter is there to prevent moire patterns and it does that by reducing the contrast that we perceive as sharpness. Post processing lets you put that sharpness back. Even photos from cameras without the filter can benefit because resizing an image can also affect edge contrast, so in your workflow, the last step before saving the image for display or printing should be sharpening. How much sharpening depends on the image, the size and intended use, so there is no one size fits all answer.
If you are not shooting news or sports, you probably don’t need an instant JPEG file and you are probably allowed to do considerable editing. Shooting raw provides you with all the sensor data. Shooting JPEG gives you a file with less than 10% of the sensor data. You can adjust the white balance with a lot more latitude if you have the raw file. If you have the raw file you can do a lot of other post processing tricks that may improve some images. Raw files take more space but memory cards and hard drives are relatively inexpensive now and while the sizes of both keep increasing, the cost continues to fall. Many news and sports photographers put two cards into their cameras, JPEG goes on one and raw files go on the other. The JPEGs are selected and sent to their agency as quickly as possible, the raw files are reprocessed at their leisure and used for their portfolios and seminars.
Ansel Adams is sometimes held up as an example of straight out of the camera. Nothing could be further from the truth. He was a master of the darkroom where he developed his own printing techniques!
It is hard to know, what you don’t know. There is a lot of technology involved in photography and also a lot of art. There is a lot of material at the bookstore and on the Internet, sadly not all of it is complete, or accurate. It is an evolutionary journey that takes a lifetime. I hope something here will spark your interest, or turn on a light for you.