Giving Up, Sadly, on Adding A CPU Chip To My Voigtländer 125mm f/2.5 Lens
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Two months I posted the report “Adding a CPU Chip to a Nikon-Mount Voigtländer 125mm f/2.5 Lens”, using a “Dandelion” CPU.

After posting the report, I spent some time actually using the lens, and could not get a consistent exposure. I thought that perhaps the aperture was not linear (that is, when the camera moved the aperture arm half way, the aperture closed something other than half way), so I re-programmed the chip so that it told the camera about the focal length and maximum aperture, leaving the actual control of the aperture back on the lens, as it was originally. I update the post, and the next day gave it a try.

It still didn't work, and I got wildly wrong exposures. This baffled me because the CPU wasn't playing any part in the per-image exposure... it just told the camera the maximum aperture, which never wavered.

So, I have no idea why it doesn't work, but I know it doesn't work, so feel obligated to report it. I'll have to yank the chip from the lens. )-:

All 5 comments so far, oldest first...

Eric Lund at Nikongear has it working as well as Bjørn Rørslett. He uses a chip he programmed himself.

Maybe you’d like to contact them?

Cheers, Dr Klaus Schmitt (kds315 at Nikongear)

I’d talked to Bjørn about the Dandelion (he hates them, and now I know why). I’ll have to check Nikongear, thanks. —Jeffrey

— comment by Dr Klaus Schmitt on June 27th, 2012 at 6:01pm JST (12 years ago) comment permalink

I can recommend Erik Lund for this type of conversion. I have just had my Lanthar 125 being chipped by Erik. He is the only one I know of that successfully has chipped the Noct-Nikkor.

— comment by Sten Rasmussen on August 31st, 2012 at 7:06pm JST (11 years, 10 months ago) comment permalink

I have a 24mm f/2.8 type C, Micro Nikkor 55mm f/3.5 type P and a 50mm f/1.4 S.C. chip added by Legacy2Digital in Oregon. They seem to work ok.

I have a 50mm f/1.2 and the conversion is too expensive and risky (rear element too large).

— comment by Daniel Chen on October 29th, 2012 at 1:08pm JST (11 years, 8 months ago) comment permalink

I would like to discuss this conversion with you. I believe I understand why it failed, but would like your view. The dandelion chip mimics a G lens (you can check this because even if you fit it to a tube or lens that does not engage the fEE lug on entry level bodies, the meter will work). If you check back to your camera manual, you’ll see that irrespective of menu selection for aperture control, when a G lens is fitted, it reverts back to the value set by the front dial. There are some work arrounds to this, but none of them good (in principle and practical working). So, I believe this CV is not AI-S (non linear aperture) and also that when you started to use the chip together with aperture selection on the lens, it just plainly confused the meter all together. The “safe” positions I guess, where just the end of line for the aperture arm, wide open and fully closed. There is a company now offering chip service to linearize non AI-S aperture operation, but it is pricey… then, so is the lens.

When I saw the results, I, too, assumed that it must be because it’s not an AI-S lens, but it’s indeed marketed as AI-S (see the Japanese manual for the lens); I talked to Bjørn Rørslett about it… he’s basically disgusted with the dandelion chips and won’t touch them. I have one other chip, so have been wondering whether I should try to pry the first out and give the second a try, but I’d probably just be setting myself up for more disappointment. The moronic implementation of focal-length-aware auto ISO in the D4 may just drive me to it, though. —Jeffrey

— comment by Antonio on November 19th, 2012 at 9:18am JST (11 years, 7 months ago) comment permalink

Hi Jeffrey,

Unfortunately, I had same way recently, many corresponding with Victor but still not success. He is very close person. And now found your post with absolutely same way and same disappoints 🙂 I have few ideas, maybe try soon to adjust the aperture lever for better work in the electronic control mode. The F60 function send to the camera something, which doing -2…3ev to camera metering. Always and all modes. I few times try explain this to Victor, but he answered finally that make this function for another targets and as I understand he does not to fix it. Seems this is not need to him. Sorry for my English. Alex

— comment by Alex on July 10th, 2013 at 6:28am JST (10 years, 11 months ago) comment permalink
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