This lens couples to the Nikon focus confirmation circuitry to make it easier to tell when it is in focus. Theoretically.
My experience is that even at f/2.8, there is a comparatively wide range of focus that results in the focus confirmation spot in the viewfinder being solidly on. A little testing today has confirmed for me that for most focusing distances, the confirmation spot is most accurate at the closest distance within any given range, i.e., if it first comes on at 2 feet (on the distance scale on the lens barrel) and goes off at 5 feet. It is the 2 foot point that is actually the sharpest.
I say most distances because I didn't get a chance to actually test it at 'infinity', such as focusing on the moon or some appropriate distant object that would serve for photographing the night sky, one of my main reasons for buying this lens. I hope to try that this weekend on a little backpacking trip. But for the object at the greatest distance that I could distinguish in the viewfinder today-a tree two blocks away-it did seem to hold true.
I'll be focus bracketing my night shots this weekend and report the results here.
My one afternoon's use of this lens last month photographing waterfalls on the Cataract Trail on Mt. Tamalpais in Marin County left me impressed with the image quality of this lens, especially considering I got I got it for just $275. Now, what will I do with all that money I was going to save for the 14mm-24mm Nikkor I had my sights set on?
