This image was one of the first I shot in the series and has the best composition for my eye. I had the lens set on 14mm- which was a mistake I believe, because the turtle was so close to the dome that his nose is soft compared to his neck, I used a brush and increased the presence and contrast in that area to hide the softness, but it's there. I have never read this, but I believe that at 10 or 11mm the Tokina Fisheye would have locked focus on his nose faster than when it is set at 14mm. Wider focal lengths give greater depth of field. Certainly the others in this series have him just as close, and are sharp. At 10-11mm this lens will lock focus on a scratch on your dome, it focuses very close.
From Ikelite Photo school