Curious AF lens incompatibility (nikon cameras, third-party lens)

A couple of months ago I bought a third-party zoom lens* cheap (28-70 made by Vitacon) with the knowledge that the AF wasn't working and that it would have to be used as a manual lens.

Ok, fine.

When I looked closer, I discovered that one of the CPU pins was missing, so I got my soldering iron out and put in a replacement. Ok, so now my F4 recognises it as a lens with a CPU (and can therefore be used in P or S modes), but the AF doesn't work. Not a problem, it could always be used as a manual lens at a pinch.

Fast-forward to a couple of days ago when I got an F90x. Bizarrely, the lens works as an AF lens for this camera.

I am slightly surprised by this, and didn't realise that the CPU communication would be different... is it just because the lens is from a cheap third-party, or is my F4 faulty in some way? (incidentally other Nikon AF lenses work perfectly with both cameras)

Just odd, that's all


* I was going to use it as a donor for the lens mount.

Probably just some incompatibility in the lens's ROM code and the exact way that it interacts with the AF module in the F4. There are all sorts of little differences in the way that different AF modules communicate with AF lenses across different generations of cameras and lenses. It's not unusual for some 3rd party lenses to act strange with some cameras, and not others. I know of some Sigma lenses in Nikon mount that don't AF with the D200, but ONLY the D200. Sigma offered a firmware upgrade if it was under warranty, but for anyone else, they were S-O-L.

Nothing to do with AF but it seems to me that an F4 deserves a good quality lens. Cheap lens on good cameras never make good pictures. The other way round is a better combination...

Point taken about the cheap lens... I got it just after I got my F4s, and the camera's no good without *some* sort of lens.

I've now got a Nikon 50/1.8 AFD, a Tokina 28/2.8 (MF), and a Nikon 70-210 (f4-5.6), so I think I'm set for a while.

To my knowledge Nikon and Canon don't share their firmware with anybody. Therefore , the third party lens makers are reverse engineering in the truest sense of the term and rarely do they get it ALL right.

Well, last night I thought I'd do a compatibility check with all of my lenses. Seems like something is awry somewhere .

I have four lenses, (2 AF Nikons, 1 Tokina AI and 1 Vitacon AF).
Of the AF lenses:

• my F4s recognises the two Nikon AF lenses, and the AF works correctly. The Vitacon lens is recognised as a 'CPU' lens, but the AF does not work.
• my F90x recognises the Vitacon AF lens, and the AF works correctly. However, neither of the Nikon lenses are consistently recognised as CPU lenses at all (the 50/1.8 is sometimes recognised, but more often - not). i.e. the camera deals with both as if they are simple AI lenses.

It's looking to me like there's something amiss with the F90x - possibly a dodgy CPU connection in the body - although the fact that one lens works is a puzzle to me:confused:.

I bet that it's going to be expensive to fix too

[I'm beginning to wish I'd stayed with my manual Yashicas]

Seems most likely that the CPU connection issue would be with the lenses rather than the body, given that the one lens works. It would seem possible that the CPU contacts on the lens mount could be worn down, possibly bent a little, corroded (slim possiblilty as I believe the Nikon contacts are gold). I'd try cleaning all the contacts - lens mount and on the body - with a little alcohol or electronic contact cleaner on a Q-tip before I rushed off to the repair shop.

There are oddities with how different bodies recognize AF from CPU contacts.

Here is a prime example (sorry to go d*****l on you for a minute).

I picked up a 500 f/4 P manual focus lens from a friend, and a TC-16A AF teleconverter. For those not familiar with the TC-16A, it was introduced with the F4 era as a way for photographers to get limited AF with MF lenses. Basicly it moves the elements of the TC a little to fine tune the focus automaticly after "roughing in" with a manual lens.

Fast forward to the modern era; the F4, F5, F6 (I think?) will recognize it as AF. So does the D2x and a few other digi bodies. But the D200/D300 will not recognize it as an AF lens without relocating a pin. The new pro body, D3, will not recognize it either. One oddity; after reloacting the pin the camera will no longer recognize the AIS aperature signals, and reports the lens as an 8mm f/1 lens. It used to register F-stops perfectly when rotating the aperature ring before I modified it. Dialing in 1 stop of exposure comp seems to get TTL metering pretty close; even though it believes the aperature is 5 stops off.

Delving into the F4 pinouts on the mount, (it's been a while, I don't remember details, sorry), it's pretty obvious that the F4 has a contact that some other bodies don't have.

I guess unless the 3rd party lens was designed with every reverse compatability in mind, you may find that it will not work on some bodies and will work on other bodies. Chances are the 3rd party company never expected inexpensive lens to ever get mounted to a top of the line pro body, and left that feature out.

Edit: Here is the link I used to modify my TC-16A. It does give pinout details for that lens maybe this will help you compare the contact arrangement of that lens with other lenes you have that work on the F4.

http://www.foolography.com/free-stuff/modify-tc-16a/

Pete, thanks for that - I will peruse it when I get home... As far as the lenses go, I could happily live with the cheap third party zoom not working at all; just as long as the 50/1.8 AFD Nikkor would work! That's the thing which is really puzzling. I will have another go at cleaning the contacts this evening, and see how it goes.

I don't know *what* might happen if I ever go digital and try to use the lenses!

Well, it must be a dirty contacts problem - over the weekend I tried different combinations and found that I could (eventually) get the Nikon lenses working with the F90x after giving 'em a wipe over. I can live with that for a while