AF Micro Adjust with zooms?

Alright, so being on holidays and having too much time on my hands I decided that I would do some micro adjustments on my lenses and calibration. First up was my 50L which was simple (albeit there's something concerning about a -20 micro adjust setting..) and then came the 24-70L which is where things got difficult. At 24mm it front focuses but is correctable with about +5 micro adjust however at 70mm it back focuses and needs roughly -10 micro adjust to bring it back under control.

Is there any way to define micro adjusts based on focal length? I'm beginning to think that with the time off I'd be better just sending the entire kit into Canon for calibration and waiting the two weeks or so to get it back

What are you talking about and how do I do it?

On the newer models such as the 50D, 5DMk2, 1DMk3 and 1DsMk3 there is a custom function for Auto-Focus Micro Adjustment which allows you to calibrate front/back focusing problems on lenses that exhibit the behaviour.

On my Mk3 it's under the C.Fn III -7 menu item which allows you to calibrate as a whole using just the camera or calibrate individual lenses.

So far it's worked great for primes but it's zooms that are the killer as Canon suggests calibrating at the maximum focal length of the zoom which then winds up throwing the wider focal length off completely for me.

That's a nifty feature, but yea I can see why it's not gonna work so well with zooms. Nice, can't wait for a new 5D MK II, I can probably afford it when the 5D MK III comes out.

No, a zoom lens can only be calibrated with one specific setting. Canon recommends using the longest focal length, as the depth of field is shortest there.
But in this case, as the OP describes it, that seems to be a moot point.

It really is quite a moot point and frankly I've come to realize why I am not the pixel peeping or chart crazed type.. after playing with the AF micro adjust on the 24-70 I thought I'd just set it back to 0 and shoot to see anything noticeable around the condo. To be honest, I can't depict any front/back focus with real world shooting on either the 50L or 24-70 so I've just reset them back to 0 on the Mk3 and will continue to use them just as they are.