Focus Clutch On 28 -70mm 2.8 Pro Sv ATX clicking when engaged in AF

I have a question about the focus clutch on the Tokina Pro Sv 28-70mm

for Nikon body. When I have pull the clutch ring in for manual

focus, while the camera body is still in Af mode, the ring has jerky

clicking, rather than smooth focus. Is this normal? I thought the

purpose of the focus clutch was for direct and quick manual focus

availability, without having to take one's hands of the lens to

switch the body into MF. Once I switch the body the to manual, the

seems to perform properly with damped Manual focus- but this require

two not so quick steps of finding the focus clutch detente, pulling

the focus ring back, and the putting the body into manual focus (now

that I think about that's actually three steps). Not exactly quick.

I suppose I could live with situation if this is indeed how the lens

is suppose to perform, but I went down to my local Helix Camera in

Chicago, and compare the focus clutch with another Tokina Atx lens

the Tokina 20-35mm 2.8 ATX (there wasn't another 28-70mm Pro Sv

available for comparison unfortunately), and with clutch ring pulled

back into MF and the Body still in AF mode, the focus ring was able

to be turned on my Nikon N80 smoothly albeit much stiffer than the

damped focus with the body in MF. There was however no clicking or

jerky movements. My 180mm 2.8 Nikon EDIF performs similiarly: I can

switch to manual focus on the fly simply by flipping a switch on the

focus ring of the Nikkor, without having switch the body into MF.

It gives me smooth, albeit stiff MF availability while the camera is

still in Af mode.

Is the Focus clutch designed to give on the fly touch up focus

similiar to Canon lenses, or is the focus clutch strickly to

disengage the focus ring with the body and lens set for AF, and

reengage the focus ring for damped Manual focus with the body and

lens both set for MF. Is the clicking and jerky focus ring movement

supposed to be there with the body in AF and lens in MF.

I bough this lens used from KEh, and received it two days ago. I

haven't had a chance to shoot with it yet, butI also noticed that

the flare seems to be much heavier (even with the hood on) in the

viewfinder than my Sigma 28-105mm 2.8-4 (a lens not known for

outstanding flare characteristics). I notice this flared streak or

line that looks like it's refracting off a speck of dirt or a

scratch, but I can find neither from physical inspection of the lens.

In fact the lens looks mint cosmetically- it's hard for me to figure

why KEH rated it E+ rather than Like New from looking at. It make me

wonder if the lens was a customer return, and whether it has more

internal problems than it would appear to have on the surface.

Hopefully when I shoot this weekend I get some answers about the

flare problem, but I don't know if I'd be totally satisfied until I

know whether that focus clutch clicking in Af mode is normal or not.

I check through previous posts on Tokina 28-70mm ATx, and have seen

contradictary info about what Tokina's Focus Clutch is supposed to do

(an not do). To keep the confusion to a minimum it might be best if

only Nikon users of this lens respond, since I understand the Canon

version operates somewhat differently.

Tokina got back to me right after I posted my question (right after I left for work). For the record here's their response:

" Tokina lenses are designed to perform (when in AF mode) with the camera in AF mode. When using the lens in manual mode the camera MUST be in manual mode also. This avoids undue wear on the motor drive in the lens. When using the lens in manual mode with the camera in AF mode this drags the gears of the lens across each other and could cause damage. "

-Glenn Nash Technical Service Representative THK Photo Products

So I guess that clicking is normal (although the 20-35 ATx 2.8 I sampled didn't do that). I going to do some shooting tomorrow and see about that flare issue.