Weird behavior of D300 with Ai, Ai-S and Ai'd lenses

[kari_karhu1]

Today, I finally tried Ai-conversion on an old Nikkor using three sources of information: (1) a table

relating the max aperture to the point where the remaining ridge of the ring should get into contact

with the lever on the body, (2) a scanned image of a lens with the same max aperture and focal length

(but a different version) and (3) a verbal explan ation on the logic. After finding out that all three

receipts were identical, I made the conversion (with the aid of my friend, a skillful tech).

 

I was very much surprised when comparing the readings on D300:

 

Nikkor 50 mm 1.4 (Ai-converted)

 

Lens: 1.4 2 2.8 4 5.6 8 11 16

 

Body: 4 4 4 5.6 8 11 16 22

 

***I made a neat table but, sorry, they are not supported but these lousy forums***

 

After rechecking twice that our procedure was correct we went on the experimental mode. After

another session of milling we finally got the smallest apertures - but NOT the largest - to align.

 

Nikkor 50 mm 1.4 (Ai-converted and experimented further on)

 

Lens: 1.4 2 2.8 4 5.6 8 11 16

 

Body: 4 4 4 4 5.6 8 11 16

 

Well, next I checked two original Ai lenses:

 

Nikkor 28 mm 2.8 (Ai-S)

 

Lens: 2.8 4 5.6 8 11 16 22

 

Body: 4 5.6 8 11 16 22 32

 

Nikkor 105 mm 2.5 (Ai)

 

Lens: 2.5 4 5.6 8 11 16 22

 

Body: 4 5.6 8 11 16 22 32

 

Thereafter I checked all my AF lenses (of D type) and their max and min apertures where correctly

mirrored by the body. Except the odd PC lens, designated as D-type and having electronic contacts but

being. as a matter of fact, a manual lens.

 

Micro Nikkor 85 mm 2.8 (D)

 

Lens: 2.8 4 5,6 8 11 16 22 32 45

 

Body: 3.8 5,3 7.6 11 15 21 32 43 64

 

Wrong again - but a different pattern. What the funny heal is going on? Yes, I checked that the camera

used the apertures displayed on the top of the body.

 

Background: yesterday I changed the tilt and shift orientation of the PC lens so that the planes coincide.

I cannot see, however, how this should affect - especially the lenses without electronic contacts.

[vivek iyer]

Can't comment on the 28/2.8 and the 105/2.5 as I don't know what you fed the camera to get those readings.

 

The PC-Micro- perhaps if you set it completely to infinity, you would see f/2.8 instead of f/3.something.

[alan_olander1664878205]

Did you enter all the lens information for the manual lenses in the "Non-CPU Lens Data", e.g. 28mm f/2.8, and then select the correct lens with the FUNC button/thumb wheel before shooting?

[photo5]

I don't have an answer, but I just wanted to say that I really enjoyed your expression:

 

What the funny heal is going on?

 

:-)

[kari_karhu1]

Just switched to Nikon - and didn't read the 421-page Finnish manual, page by page. The

first lens to buy was that PC 85 and since it worked right-away and I knew its manual

(albeit D) type, I didn't imagine something like telling the body what lens is on is needed.

My mistake.

 

But still one problem remains and one (possibly) new opportunity arises. (1) Why did the

PC 85 act like it did? (2) Provisionally, it seems that CPU-less Ai, Ai-S and Ai'd lenses that

have the max aperture of 4 or worse need NOT feeding lens data in the menu - if you do

what I did when proceeding with milling further than described in the Internet sources.

 

I think many readers would benefit from a response on (2) and as far as (1) goes I'd like to

know whether I did something wrong with my PC 85.

[vivek iyer]

Check what I posted. Your camera is most likely reading the effective aperture from the PC Micro. Set it to infinity and see if you can get f/2.8.

[dzchang]

I think you need to enter the Non-CPU Lens data. There are two things you need to tell the camera: the focus length and the biggest aperture. The AI, AI-S system use a step ring to tell the body what aperture you are using, and it starts with the biggest aperture. If you do not set the camera with correct data of the biggest aperture, it can not response to the bigger one.

 

I think your D300 come with a default biggest aperture setting of F4, and when you apply the 50/1.4 on to the body it can not tell the aperture bigger than F4. I believe by setting this data you will get the correct responding on the body.

[kari_karhu1]

Thanks, all, for your answers. The behavior of the modified PC 85 is still a mystery. Yes, I did

focus at infinity when getting 3.8 instead of 2.8 and 64 instead of 45. Has anyone made

similar conversion?

[bjørn rørslett]

The 85Pc will go to f/3.8 when the focusing collar is rotated *precisely* 90 degrees. My hunch is that you made a mistake in the modification of the lens. Is true infinity focus achieved after the modification?

 

I just modified my 85PC and verified that the inifnity focus aperture still is f/2.8 no matter how the angle of tilt is to the shift axis. The two small locking knobs now are lined up together at the same side of the lens barrel. Is that the case with your 85PC too?

 

The D300 makes no assumption of the maximum aperture of any non-CPU lens. If the readings starts at f/4 *and* you have entered the correct lens data into the camera, the AI modification is in error. But all of this presumes that you have the correct lens selected in the camera of course. If you set the camera to accept an f/4 lens and swapped lenses later without setting the new data, the camera will still think it's the same f/4 lens that is mounted. But the minimum aperture reported could be different of course if the new lens didn't run over the same number of aperture stops.

 

I once had an 8mm f/2.8 lens that a local shop did a makeshift AI-conversion of and it insisted being an f/5.6 lens afterwards. I later got the proper factory AI-kit for it, so now it is again f/2.8.

[kari_karhu1]

The problem is - as the title of the thread aptly suggests - in the body.

 

As regards CPU lenses, my D300 may read the apertures correctly for a while and then,

without any apparent reason, it slides, e.g., to 3, 3.5, 3.8. 4 or 4.5 instead of 2.8. This

behavior was tested in dozens of sessions, each with several lenses owned by me, a local

dealer and a knowledgeable Nikon Nordic employee. The reason may be physical (but the

contacts seem to be clean and they are serving their second week, anyway) or electronic.

Will report later which one.

 

I'm sorry for having disturbed you with trivial misunderstandings on using non-CPU

lenses and making Ai-conversion. On my defense I may be allowed to tell that the weird

behavior of the body conformed my erroneous assumption on how Ai-converted lenses

communicate with modern bodies.

[vincenzo_maielli]

Have you informed the D300 about focal lenght and maximum aperture of the AI lenses, before mounting?

Ciao.

[kari_karhu1]

This is getting really interesting with the problematic MODIFIED Micro Nikkor PC 85 and

my D300.

 

Today, I decided to experiment with focussing. Everything went fine - as far as the

distance was just less than infinity. The last few movements of the focussing ring resulted

in erroneous aperture readings.

 

So, I reopened the lens and learned that one of the two electronic strips folded by black

tape was in quite a tension. After removing the piece of tape I disconnected and

reconnected the strip, put everything together and, voila, everything worked!

 

What about the odd behavior of other CPU lenses? This is the interesting part.

 

I didn't take notes but I'm pretty sure that all other lenses performed well provided that

the PC 85 had not been on the same body "in bad mood" since the last boot of the body.

In other words, I assume that a PC 85 (and any other CPU lens - why not) having a weak

connection that sometimes works well, sometimes doesn't somehow confuses the D300 to

treat every other lens with an equal aperture offset.

 

You bet I'm not going to prove my hypothesis experimentally.