Quasi conversion for mounting non-ai on D70

[watts1]

I recently upgraded from an F2 to a D70. Previously I had no need

for AI lenses and have enjoyed snapping up some fast glass off ebay

cheap. My favorite lenses are my 50mm 1.4 and 105mm 2.5 both non-

AI. I have enjoyed the D70 kit lens for its versatility, but I love

my manual lenses for their ability to shoot in low light, and thus my

dilemma...

 

It will be some time 'til I can save for some new AF lenses (1st on

the list is a 50mm 1.8) I've got an event this weekend which will go

well into the night and I don't believe the kit lens is going to meet

my needs.

 

Since I waited this long to upgrade, I do not believe I will be

buying a camera with a fixed metering tab. The only other autofocus

camera I have is an N50 and it lacks the metering tab as well. I

have a handheld meter that I don't mind using, supplemented with the

histogram display on the D70.

 

And now my question: Do I really NEED to do a full AI upgrade to

properly mount my lenses on the D70 and N50? I am planning on just

notching the aperture ring so it clears the minimum aperature

switch. Am I missing something else?

 

Thanks,

Watts

 

Here are some pictures of this event from last year:

 

http://www.photo.net/photodb/edit-presentation?presentation_id=265435

[david_h._hartman]

Yes, you may damage your lenses and you will reduce their

value. If you are going to modify your lenses for use on your D70

either have this done properly by a repair service with a

reputation for doing it right or learn what you need to know to

do it yourself. I did an AI job on a 105/2.5 IC and the finished

results were great but I nearly butchered the lens because I did

not know that the screws on the bayonet were locked with a thread

lock similar to Loctite, white high temperature thread lock. I

torqued the head off one screw and it took me several days to

figure out how to remove the screw. I had two other 105/2.5(s),

an AI and an AIS so I was able to get a perfect match with the

aperture coupling ridge on these. <br>

<br>

If you file the aperture control ring without removing it you

will very likely get aluminum fillings inside the lens and

helical which could render the lens useless buy binding up the

helical. If either of your lenses have no screws on the rear

bayonet then you should probably just forget about using these

lenses with your DSLR. I hesitate to advise anyone to do there

own AI job but some are quite capable of doing this for

themselves. Camera repairmen and women put there pants on the

same way the rest of us do. The dont just jump into them

but they have training, documentation, tools and experience

including butchering a few cameras and lenses.<br>

<br>

Anyway if you are going to do it, do it right!<br>

<br>

Good luck,<br>

<br>

Dave Hartman.

[watts1]

David,

 

Thank you for your response. I understand where you were coming from in regards to doing more harm than good. I had considered sending these lenses off to be converted by John White. There were two reasons I decided not to though. First, I only paid $40-50 each for these lenses, and had a hard time justifying $35. Second, I waited too long and I need them this weekend. So I decided to push forward and try it myself, and maybe learn something in the process. If nothing else I knew I could get another lens off ebay (this time I'd get AI).

 

I started with the 105mm 2.5. As you warned, both of my lenses are the kind without screws on the bayonet. But I looked closely and found three small screws on the bayonet lugs. I removed these and the baffle pulled out. You can then see the spring that returns the aperture. It turns out you don't even need to remove these screws on this type lens. There is one screw on the aperture ring that links internally to the aperture yoke.

 

Removal of the aperture ring is simple. First, set the lens to it's minimum aperture (in this case F22.) Second, remove the screw on the aperture ring. Third, unscrew the aperture ring until it comes off.

 

Once I had the aperture ring off I decided not to do a full AI conversion, but only remove the portion of the ring that was interfering with proper mounting by hitting the minimum aperture switch on the camera body. According to this chart: http://www.chr-breitkopf.de/photo/aiconv.en.html#ai_pos the correct postion for the AI ridge would be at f11 2/3, requiring removal and remounting of the control yoke for use on my F2. This proved to be more trouble than it's worth since I don't own any bodies that meter with ai lenses.

 

To determine correct position for removal,I placed the aperture ring against the camera body with the minimum aperture at the top and marked where the minimum aperture switch fell. Then I set the lens to maximum aperture and lined it up in the mounting postion, again marking the position of the switch, accounting for the throw of the switch. Then all that remains is to carefully file the ring down between these two marks. Since the minimum aperture switch has no effect when mounting non cpu manual focus lenses, I could have removed even more, but filing is tedious and I didn't want to do more than I had to. If you decided to do this, please do not file in the vicinity of the lens so you don't get filings in it. Care must be taken not to mar the thread in the inside of the aperture ring. After finishing, wipe down the threads to remove filings.

 

When reinstalling the aperture ring I screwed it in until it bottomed out and then unscrewed it two full turns and lined it back up to the minimum aperture. The screw should go right back and line up with the aperture yoke inside.

 

And... you're done.

 

In the end, it was a very rewarding experience. I will put the modified lens through it's paces tomorrow and then modify 50mm 1.4.

 

The following links were very helpful:

http://rick_oleson.tripod.com/index-107.html

 

http://www.chr-breitkopf.de/photo/aiconv.en.html

 

http://www.zi.ku.dk/personal/lhhansen/photo/repair/aimod/aimod.htm

 

http://www.aiconversions.com/compatibilitytable.htm<div></div>

[watts1]

<div></div>

[lex_jenkins]

Hmm... my non-AI'd 180/2.8 Nikkor is sitting in the other room. Where're my files and moto-tool?

 

Hang on, aren't there screw in replacements for some Nikkors? Assuming you can still find 'em.