Lots of new photo products come our way throughout the year, and when this one arrived, the SpyderLensCal Lens Calibration Systemwe made a call to the company.
It went something like this: “Really? Our lenses are tack sharp and why on earth would we need something like this? And for $60.??? Fine. We’ll try it out, and get back to you.”

OK, to start off, it was packed flat and set up easy.
We got 2 tripods out and set the testing area, following the easy steps.
Now we had never seen the focus adjustment section on our camera before. or paid attention to it anyway.
There, in the Wrench section, a was the AF Fine Tune. OK, ready to test.
First up was a 24-70mm 2.8 Nikon lens on a D700.
Woah. Slightly off, with a +7 correction.
Moved onto our other lenses that are usually thrown in the bag, and sure enough, off just a little on each.
The AF Fine Tune corrected it all and once re-tested, all was as it should be.
Up to 20 lenses are able to be stored in the camera, so each time the specific lens goes on, the corrected calibration kicks in and you are set.

Check the video for a real life look at the unit.

In hindsight, we knew something may be up, but felt it was operator error. The focus point chosen, was slightly off.
Nope.
It also proves that there is a reason to having the AF fine-tune function in the first place; every camera body and lens may not react exactly the same, once coupled.
Look at the list of cameras that have this feature:

Supports autofocus adjustments:
Canon (50D, 7D, 5DMkII, 1DMkIII, 1DMkIV, 1DsMkIII, 1DIV)
Nikon (D300, D300s, D700, D3, D3s, D3x)
Sony (A850, A900)
Olympus (E-30, E-620)
Pentax (K20D, K7D)

There are some other solutions to this problem, but this is the one that opened our eyes.
You may not need to tune your gear like a fine Italian sports car, but you can’t ignore maintenance either.
At $60. it may seem like a lot, but use it twice a year, stay sharp, and maybe even share it with a friend.