Summicron-S 100 mm – Aperture Stuck? Underexposing by 2–3 Stops

[Stef63]

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Of all my S lenses, the Summicron-S 100 mm is — together with the 120 mm — my most beloved lens.

Recently, however, I noticed a very strange behavior: the lens consistently underexposes by about 2 to 3 stops. Also, the diaphragm does not fully open at f/2.0. When I use the stop-down button, it’s clearly visible that at f/2.0 it’s already partially closed — and with each click it closes further, step by step, all the way down to f/22. In other words, for every aperture setting on the camera there is a corresponding physical opening, but it starts off wrong from the beginning.

I also see the same behavior when using the lens on an SL2 with adapter, so it’s definitely not camera-related.  No other S lens has this problem on my S3. 

Apart from the obvious advice to send it back to Leica for repair — has anyone experienced something similar, or does anyone have suggestions on what might be going on?

[John McMaster]

On my just serviced 100-S, if I come up to it I can barely see the diaphragm.  However, if I stop the lens down with the stop-down to say f8.0 then open it up to f2:0 I can see more of the diaphragm....

john

[Milan_S]

Hi @Stef63 sorry to hear this. I am also Antwerp based, so I can have a look at your S3 and Summicron-S since I have the same combination. 

We can compare both cameras and lenses and swap it to see where is exactly the issue. 

[Pieter12]

Interesting. My 100 was just serviced. I tried stopping down, previewing and letting the diaphragm open back up again--I could see the edges of the blades. After doing this a number of times at smaller and smaller apertures, the blades opened back up completely. I don't think it will affect exposure in any significant way since the difference between wide open (no diaphragm visible) and the slight intrusion of the blades seems minimal. But it certainly is bothersome on a lens that just came back from Wetzlar.

[Stuart Richardson]

I had a Hasselblad 110 f2 that did this. I think in fast lenses with a lot of glass in the barrel there is not a lot of room for the iris and the designs require more complicated action, when compared to slower lenses with more space in the lens barrel. In my lens the blades would slightly bind, causing it to catch a bit at certain apertures, rather than fully opening and closing. Service fixed it up. Perhaps you have the same issue.  

[Stef63]

18 hours ago, Milan_S said:

Hi @Stef63 sorry to hear this. I am also Antwerp based, so I can have a look at your S3 and Summicron-S since I have the same combination. 

We can compare both cameras and lenses and swap it to see where is exactly the issue. 

Hi Milan, thanks a lot for the kind offer — I really appreciate it. I’ve sent you my contact details in a DM so we can arrange something.

[Pieter12]

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Coincidently, I had the same issue just yesterday with my S100 that had just been serviced by Wetzlar. It had the AF motor upgrade, along with all the adjustments Leica makes when doing that service. All the shots were 2-3 stops underexposed. I looked at the diaphragm action using the preview button and it seems to be stopping down and returning properly. I also used an S45 during the same shoot and those images look fine. I don't think it is the camera, the lens is going back to the Leica Store on Tuesday.

[Pieter12]

At the Leica Store this morning, the woman detected that the lens was making a faint, strange noise while idle. That is probably related to the problem, art least for my lens.

[Stef63]

14 hours ago, Pieter12 said:

At the Leica Store this morning, the woman detected that the lens was making a faint, strange noise while idle. That is probably related to the problem, art least for my lens.

Mine behaves a bit differently — and unlike yours, there’s no strange sound involved. The aperture seems stuck (powered off or in its supposed “fully open” state) at what I’d guess is around f/4.

When I hit the aperture preview button, it does a lightning-fast move: opens up fully for a split second and then snaps right back to that same semi-closed position. You’d expect it then to stay the same between f/2 and f/4 and only start closing beyond that — but no, even at f/2.4 or f/2.8, it insists on closing even further, giving me underexposure at every setting on the S3.  Just as if it believes f/4 is the new "starting" and fully open position. 

What makes it even weirder: on my SL2 with the S-to-L adapter, the blades behave exactly the same, yet the exposure is spot-on on the SL2. I assume SL meters light differently — though for now, I still can’t figure out what mysterious sequence of events makes two cameras react differently to the same (obviously defect) lens.

Edited October 22 by Stef63

[helged]

4 hours ago, Stef63 said:

Mine behaves a bit differently — and unlike yours, there’s no strange sound involved. The aperture seems stuck (powered off or in its supposed “fully open” state) at what I’d guess is around f/4.

When I hit the aperture preview button, it does a lightning-fast move: opens up fully for a split second and then snaps right back to that same semi-closed position. You’d expect it then to stay the same between f/2 and f/4 and only start closing beyond that — but no, even at f/2.4 or f/2.8, it insists on closing even further, giving me underexposure at every setting on the S3.  Just as if it believes f/4 is the new "starting" and fully open position. 

What makes it even weirder: on my SL2 with the S-to-L adapter, the blades behave exactly the same, yet the exposure is spot-on on the SL2. I assume SL meters light differently — though for now, I still can’t figure out what mysterious sequence of events makes two cameras react differently to the same (obviously defect) lens.

SL meters the light from the sensor. S3 does the same when you are in live view. So you may run a test or two with S3's live view activated; I would guess it behaves as on SL.

[helged]

And since we/some are talking about S100 - are there any S100 for sale, somewhere around?

[Stef63]

1 hour ago, helged said:

SL meters the light from the sensor. S3 does the same when you are in live view. So you may run a test or two with S3's live view activated; I would guess it behaves as on SL.

Your guess sounds logical, but on the S3 both live view and non–live view images are underexposed, and only with my 100 mm.

I can’t quite explain it, but somehow the S3’s light metering seems to take into account the aperture value the lens miscommunicates to the body — and it does this differently from how the SL2 handles it.

[Stef63]

1 hour ago, helged said:

And since we/some are talking about S100 - are there any S100 for sale, somewhere around?

It took me months of almost daily browsing through the usual suspects — eBay, MPB, the classic Leica online store…

I finally found one at Leica Portugal, though it was missing the hood, which led to another six-month search. During that time, I only came across one Summicron-S 100 mm on eBay in the US — and that was already half a year ago.

Along with the 45 mm and 120 mm, they seem to have completely vaporised.

Good luck hunting one down — it’s absolutely worth the effort.

[Pieter12]

9 minutes ago, Stef63 said:

It took me months of almost daily browsing through the usual suspects — eBay, MPB, the classic Leica online store…

I finally found one at Leica Portugal, though it was missing the hood, which led to another six-month search. During that time, I only came across one Summicron-S 100 mm on eBay in the US — and that was already half a year ago.

Along with the 45 mm and 120 mm, they seem to have completely vaporised.

Good luck hunting one down — it’s absolutely worth the effort.

How hard was it to find a hood? I need one. In the meantime, I have been using the S70 hood--better than nothing. BTW, my S100 came from Adorama.

Edited October 22 by Pieter12

[Stef63]

15 minutes ago, Pieter12 said:

How hard was it to find a hood? I need one. In the meantime, I have been using the S70 hood--better than nothing. BTW, my S100 came from Adorama.

Well, actually, I didn’t find it myself. The hood was originally included in the package shown on the Leica Portugal website, but before shipping, they informed me they had “lost” it.

It then took them six months and several reminders to Wetzlar before it finally turned up. Where they found it — in a drawer at the store or somewhere deep in Germany — remains a mystery.

In the meantime, I used the S70 hood as well.