35 mm f/1.4 AiS - lazy aperture mechanism

[beryllium10]

Today I looked at a used 35 mm f/1.4 AiS in a local camera store.  I put it on my camera in aperture-priority mode and shot a test sequence from f/1.4 up to f/16.  To my surprise the shots from 1.4 to 4 were correctly and equally exposed, but from f/5.6 on up they became more and more over-exposed. It took a bit of head-scratching to figure this out. Eventually I looked at the aperture blades when pressing the DOF preview button.  They snapped down nicely to about f/4, but closed very lazily after that.  It took the mechanism 1-1.5 seconds to close fully at f/16 (actually quite nice to watch it glide slowly closed).  Clearly the aperture wasn't able to keep up with the shutter when set above f/4.  The actuation lever felt about right (not tight or obstructed or visibly bent), so I think one or more aperture blades must have a sticky spot.

Has anyone else encountered such a problem with their copies of this lens?  How difficult would it be to disassemble, clean and re-assemble the diaphragm?  It's a CRC lens, so my guess is that disassembling / re-building it isn't for the faint-hearted.  I'm not an experienced lens surgeon.

Thanks for all thoughts and advice,   John

[richardHaw]

most probably oil in blades.

[David H. Hartman]

This is frequently caused by lube contamination. Oil separates from the grease and contaminants the aperture blades. It will get worse in time. That would be my first guess. It's a problem with many different manual focus lenses.

Dave

[beryllium10]

Thanks Richard, thanks Dave, I thought it likely so.  Wonder if the lens was once left in the sun to cook for a while, or stored in a warm cupboard some time in its history (though internal glass surfaces looked clean).  I've not encountered this with other manual focus lenses, but maybe I will see it again as my lenses (and I) grow older. 

Cheers - John

[richardHaw]

ill show you a video if i knew how to post it here

[Erik Lund]

Seen this before, super difficult to find out why, find another sample, there are plenty of them,,,

[beryllium10]

Thanks Erik, interesting to know that you've seen this before.  I had never seen a 35/1.4 before and was intrigued after reading about it on this site.  Not actively looking for one, but might be tempted if a nice one turned up locally at a good price.  An insidious problem that develops after discovering this site ...

Cheers,  John

[pluton]

I had a similar scenario with my current 135/2 AiS. Several years after I had purchased it used, it suddenly developed the slow aperture stop-down disease.  The local repair guy had to take three or four passes at it, but he did finally fix it. I'd skip that sample, unless it is super cheap.

[David H. Hartman]

I have a 50/1.4 AIS Nikkor that I suspect was baked in the trunk of a car. It was twice quick cleaned by a friend only to become lube contaminated again. It will require a full strip and relube. I bought a proper spanner wrench and a set of cameras lens grease but I've never found the time.

Does anyone here have experience with a quick cleaning where the aperture assembly is bathed in solvent but the helicoid is not stripped of the old grease? Does this kind of cleaning usually fail?

Dave

[Erik Lund]

It is possible but difficult,,, but the cause could be elsewhere,,,

[longzoom]

Thanks Erik, interesting to know that you've seen this before.  I had never seen a 35/1.4 before and was intrigued after reading about it on this site.  Not actively looking for one, but might be tempted if a nice one turned up locally at a good price.  An insidious problem that develops after discovering this site ...

Cheers,  John

  If the price is very tempting (say, $200-250), and condition of the lens is OK or even better, you may get it, cose cleaning shouldn't be that much, $50-75. Sometimes, keeping the oiled lens with front element up, may help, but after every usage do not forget to turn it up, immediately. If you have no skills, do not touch(open) it yourself, cose you may not return the CRC block to the right position.  LZ

[Erik Lund]

Is that worth the effort if you end up with a lens with a lazy aperture?

[longzoom]

Is that worth the effort if you end up with a lens with a lazy aperture?

  If you asking me, its definitely worth, because to fix it gonna take me less than 2 hours. Can't say anything for anyone else. THX!  LZ

[richardHaw]

I will buy it for $50

[beryllium10]

Richard - unfortunately more than $50!  I don't think the store had noticed the problem.  Now they know it's not fully functional I think they'll acknowledge the fault and bring the price down, but I don't know where it will land.  Could be a good deal for someone who likes to shoot this particular lens wide open.  Thanks to all for your thoughts and advice.  I've decided I'll pass on this one, but have learned a few things I didn't know previously!

Cheers - John