How do lenses get calibrated?

What is the process? Do they take the lens apart? I'm curious ...

Wow! Well that's a first! No body knows? Or are you guys pissed and not talking to me ...?

AFAIK, they mount the lens to a "Golden Sample" body that's on a calibrated rig of some kind.

Knowing the body is "perfect" as are the conditions under which the test is being done, they can then go in and tweak the elements of the lens (set screws? shims?) to bring it within spec.

FlyingPhotog wrote in post #7952660
AFAIK, they mount the lens to a "Golden Sample" body that's on a calibrated rig of some kind.

Knowing the body is "perfect" as are the conditions under which the test is being done, they can then go in and tweak the elements of the lens (set screws? shims?) to bring it within spec.

Exactly how they do it

I see, thanks! So the lens does get disassembled (partially at least)?

I was told on my L lenses that I had recalibrated, that they do it electronically, there is a chip apparently in the camera and I guess the lens gets mounted on the test machine and they do the computer thing to make it right. I've been told this several times when I took something in to have it sent off to Canon to be calibrated.

Honest question... why aren't they calibrated from the factory. It really blows my mind that a $1500 lens may or may not focus correctly, who knows.

I have noticed with the 100-400 I have had in lately, it comes back with the distance switch set on 1.8 or whatever the short distance is---I wonder if all the focus stuff is the same other than distance or if some of the circuit is changed (as in if long distance focus uses exactly the same as short distance).

Jannie wrote in post #7952869
I was told on my L lenses that I had recalibrated, that they do it electronically, there is a chip apparently in the camera and I guess the lens gets mounted on the test machine and they do the computer thing to make it right. I've been told this several times when I took something in to have it sent off to Canon to be calibrated.

That makes sense. They usually ask for the body when you send in a lens for calibration.

This is what I believe happens. The chip in the lens gets calibrated. They adjust the reaction it will have to the signals from the camera. This is assuming none of the elements are out of whack. Someone posted that for a zoom, they adjust at 8 different focal ranges. This is one reason why MA in the newer cameras is of limited benefit with zooms.

When they ask for your body after a calibration does not give the desired result is that both bodies and lenses are calibrated to within a certain tolerance, lets say -5 to + 5

If the body, within calibration falls on the -4, for example, and the lens, also within spec, falls on the +5 side, they may be both in spec but at the opposite ends of the allowable tolerance. This would give you fairly crappy results. So, when they ask you to send both in, I assume they will both be calibrated to the center of the acceptable tolerance scale. i.e. 0. The camera will still work fine/better with other lenses and vice versa.

So if this is the case, then sending a lens alone without the body for calibration is more or less a shot in the dark still. Isn't it?

bohdank wrote in post #7953175
This is what I believe happens. The chip in the lens gets calibrated. They adjust the reaction it will have to the signals from the camera. This is assuming none of the elements are out of whack. Someone posted that for a zoom, they adjust at 8 different focal ranges. This is one reason why MA in the newer cameras is of limited benefit with zooms.

When they ask for your body after a calibration does not give the desired result is that both bodies and lenses are calibrated to within a certain tolerance, lets say -5 to + 5

If the body, within calibration falls on the -4, for example, and the lens, also within spec, falls on the +5 side, they may be both in spec but at the opposite ends of the allowable tolerance. This would give you fairly crappy results. So, when they ask you to send both in, I assume they will both be calibrated to the center of the acceptable tolerance scale. i.e. 0. The camera will still work fine/better with other lenses and vice versa.

Could be. How do your other lenses perform on your body ? I have no issues with any of ny Canon lenses.

I sent my Tamron in, without body and it absolutely rocks now. If it comes back not much better than you'll probably have to send the lens and body in to Canon. If they ask for that I would insist they accept all my Canon lenses and check them all.

bohdank wrote in post #7953323
If they ask for that I would insist they accept all my Canon lenses and check them all.

Yah, I'd do the same thing.