sprocket i/o

Nikon D300 AF Fine Tuning: AF 70-300mm +0 and +15 adjusted

I haven’t talked about it much on my blog yet, but two weeks ago I got my Nikon D300. I bought it primarily because my Nikon D70 was acting up, but having the latest & greatest in gadgets doesn’t hurt either. Of course, as I was boxing up the D70 to send back to the factory after a week of CHA errors, my old D70 began working again.

I’ll leave a full review for a later day, but I wanted to share one of the most amazing D300 features: AF Fine Tune. Over time, a lens may settle in, and it’s focus may not be exactly like it was at the factory. I prefer buying my lenses off of eBay, and have had pretty good luck except for one purchase: the Nikon AF 70-300 F/4.0-F/5.6G. The picture quality of this lens always sucked, but I just chalked it up to how cheap the lens was ($150). Internet reviews seemed to agree that this lens was garbage, but there were dissenters.

Since I left my birding lens (Sigma 50-500mm) in North Carolina over Thanksgiving break, I’ve been stuck with the 70-300mm for birding. The results were really bad, and even worse with the Kenko Pro 1.4X converter that I am using to bring the range up to 420mm. After reading several forums, I got to thinking that maybe the problem with my copy of this lens isn’t that it’s garbage, but that it’s auto-focus needs tuning.

Unlike most digital camera’s, the Nikon D300 allows you to fine-tune the AF of each individual lens in your collection. You plug the lens in, and select your compensation value (-20 to +20), take some photos, and see which one comes out the best. After reading the perfectionist approach to AF Fine Tuning, I decided to take things a bit more haphazardly. I simply slapped the D300 up on a tripod, extended the lens out to 300mm, set my aperture to F/5.6, and took some photos.

My first sample was a screwdriver with a label at -20, -10, -5, 0, +5, +10, +20, and inspected it on the computer. After comparing photos side by side, the photos between +15 and +20 looked the best. I photographed a label of Julmust at +13 to +20, and settled on +14 to +16 looking the best. I tried one more time with another DIMM, this time with flash. After looking at the photos on my computer, I decided that +15 was the perfect compensation amount for this lens.

You can see the difference between +0 and +15 in the photo attached to this entry. While it did not magically make the lens tack-sharp, there is a very clear difference in the amount of detail between the two shots. I’m really curious what it’s going to do for the 50-500mm.