I have to admit that despite my technical knowledge about all the controls on a DLSR camera, I really know very little when it comes to achieving tack sharp images. I hope all this is about to change with the time and research I have invested in the last few days.
All the information I ever got in any photography course about focusing was not enough to get me there. Typically, the lessons cover camera holding technique, use of tripod and remote control, and correct setting of minimum shutter speed. The more advanced topics may cover hyperfocal distance, and use of mirror lock up to reduce camera shake.
With the above knowledge, I have never really mastered the art of getting consistently tack sharp images. Therefore I jumped at the opportunity to read a book called "Tack Sharp" by James Brandon when I signed up for a special 5-Day Deal on photography. The book did not help me at all (later, on re-examining the book, I found that it did cover the important camera settings I am going to talk about) but it did trigger me to do something about it.
I pasted some printed papers on the wall and started target shooting practice. Fixing the shutter speed at 1/50 sec, I got some disastrous result; I have over-rated myself at my own hand holding stability. I increased it to 1/80 sec (i.e. I was shooting with 24-70mm lens) I started to get better focus more often. Therein lies my Discovery No.1: the experts were right. The minimum hand held shutter speed must be faster than 1/(focal length).
Discovery No.2: Using another camera, the Olympus OMD-EM5, I managed to achieve consistently sharp focus even when hand holding at 1/45s on the equivalent of a 90mm lens. The image stabilizer actually works! Previously I was using a Nikon D700 which has no image stabilizer.
Discovery No.3: I "discovered" that many pro shooters out there actually (not surprisingly...) use the fancy camera settings available on the higher end DSLR. I re-discovered the back button focus "AF-On", which allows me to focus using a separate button other than the shutter release. I also learn to take advantage of the AF-C servo focus. I also learn when to use the Single Point AF and when to use the Dynamic auto focus to achieve better result.
Discovery No.4: My OMD-EM5 with a simple $250 45mm lens, does a far better job at focusing than my D700 with a ~$2000 24-70mm lens.
Now that I think I have a better understanding about focusing, perhaps I might next learn the fine art of lens appreciation. Frankly, with all the wonders that a simple bit of photoshopping can do, I am not a big connoisseur of lenses.