Gear tested: Canon 50D + 85 f/1.8 vs Nikon D90 + 85 f/1.4
1) To test AF consistency under incandescent lights, shots of 3 AA batteries positioned in a diagonal line are taken. Camera is tripod mounted and only the center AF point is activated. In between shots, the lens is either defocused to infinity or minimum focusing distance. 30 shots are fired for each combo.
Canon 50D nails this test completely: every shot is spot-on.
Nikon D90, on the other hand, is not so reliable in this department. Shots can either be very slightly front or slightly back-focused or spot-on. Without the aid of the AF lamp, Nikon AF can sometimes go way off mysteriously.
2) Good Light Autofocus (ISO 100, f/1.8 and consistent shutter speed between the two cameras)
a) Similar test as (1) is administered save the target now falls on some contrasty window grills in an apartment block under sunlight illumination.
b) 50D AF results: Sharp (19/30), Slightly OOF (10/30), Unacceptable (1/30)
D90 AF results: Sharp (6/30), Slightly OOF (9/30), Unacceptable (15/30)
c) To confirm if the dismal D90 results are due to poor calibration or simply an under-performing camera, the shutter release was pressed half-way repeatedly. Under these conditions, the distance marking on the lens is observed to twitch all over the place... there is absolutely no consistency. To observe such erratic behavior under broad daylight is shocking.
Fully expect the D5000 to perform similarly since it uses the same awful AF sensor
3) Overview:
When it works, this is what it looks like (center portion only):
Unfortunately, HALF the time the D90 AF does not work and this is what I get:
4) And this is what a full time professional photographer thinks of the D90 AF: "the D90 is a very lightly warmed over D80 with a softer sensor and a couple of lame gimmicks added but retained the same lame AF" (taken from
here)