Light leak from lens mount? Help needed!

[coelacanth]

I'm hoping knowledgeable RFF members can help me find the cause of this light leak.

As you can see around the right bottom corner in the sample pics, it looks like a mild light leak which I first thought something OOF object in front of camera.

I've shot at least 10 rolls with camera so far (new to me), only very very few had this problem under strong sun light right above the camera. (or shot slightly against it) After I figured this is not OOF stuff, I tested with an LED light. Lens cap on, shutter curtains open, looking through behind the camera. I see slight amount of light coming in from right below illuminator window side of lens mount (not through window). You can see it when the LED light is angled at right angle, very close only. (top right corner facing camera front)

This is a new MP (first 1000 produced). Lenses tested with are relatively old (well, in Leica standard anyway 😉). 1966 Elmar 50/2.8, 1971 Summicron 35/2, Leitz LTM/M adapter (not sure of age). Within my experience with M3, M2, M4 and M6 classic, this MP with my lenses is the lightest (loosest) mounting resistance although it's not "real loose" loose. Lens' base surface are quite smooth without any obvious scratches or bumps. I haven't seen this leak with, for example, M6 under bright daylight/similar light angle. And the previous owner didn't encounter with this problem with his several new lenses under bright SoCal daylight (I'm in NoCal).

I'm assuming the slightest looseness of the lens mount that's within factory specs and lenses relatively old (although good condition) might be working against each other.

Do you have any idea/suggestion/experience with a light leak like this? Will it be somewhat minor "adjustment" level repair on the MP mody? Does this mean my lenses need major parts replacement?

Any input would be greatly appreciated.

 

[Livesteamer]

I seriously doubt that your lens mount could be loose enough to leak light. There are baffles in front of the shutter that can leak. A problem I have had, and it looks much like this, occurs with my 35 Summilux from 1969. It is so small I sometimes get a finger into the field of view of the lens. It looks much like what you've got. Joe

 

[coelacanth]

Joe,

Thanks for the input. I, too, think that the lens mount can't be so loose it's gonna leak light. And the light is shown (when I look through with LED light) only around the area described above, about 1/4 inch wide, of the mount. But it is around the mount. I'll try to take picture of the LED test later. Still not sure what's causing it...

 

[chenzhaohy]

If the lens mount leaks, it will ruin whole picture,not just a corner, because it is far away from film.
I guess it is the shutter's problem which only happens at high speed.
I once talked to DAG and he told me that the lubrication of MP shutter is not right as before and it will cause issues.
I may be wrong, hope it can help.

 

[coelacanth]

Thanks chenzhaohy. I can't be really sure the light I see with LED test is the actual cause of the leak in the pics. It's so slight, maybe that's the way it is and nothing to do with the leak in the pictures. I don't have another M body at the moment to see if that's normal (light from LED test that is).

 

[coelacanth]

Oh another thing. I'll have to look through all negs (I have scanned only those look worth scanning from negs), but in real life, I've seen the leaks with Summicron 35/2 only so far. But the with LED test, other lens/adapter&lens showed same amount of light looking through the back door. And I the mounting resistance is light with all lenses I tried. But again, I didn't think it was too loose.

So if the problem is not with the light from mount, then the lens might be the cause. But then how? Cron's base is smooth, recently CLA'd. I doubt this is any type of flare or ghosting.

 

[MikeL]

Sug, are you sure this isn't a finger like Livesteamer mentioned? When I first bought a nikkor 35mm f1.8, which is pretty flat, I had a bunch of photos with finger glare in them, looked just like that. The summicron is pretty small too.

 

[coelacanth]

Thanks Mike.

I, too, thought that was my finger or something, but I can't really imagine how it can get in the way. I have A&A's very short cloth strap that's either around my neck or tightly wrapped around my wrist. I can't imagine that's getting in the way, especially it should be right around VF window to cause this problem. All sample shots were shot horizontally, and the Cron version 3 is not the shortest of its kind and had an ND8 filter on it. I wore a hat like the one in my profile pic, but it does not stick out anywhere close to problematic level no matter how tightly I hold the camera against my face.

Looks like I need to do more testing to narrow down the cause. Unfortunately San Francisco isn't seeing much of sun today, so I guess first test would be with LED light against a test roll.

 

[ferider]

Sug, are you sure this isn't a finger like Livesteamer mentioned? When I first bought a nikkor 35mm f1.8, which is pretty flat, I had a bunch of photos with finger glare in them, looked just like that. The summicron is pretty small too.

It does look exactly like it. Happens to me occasionally when using a grip and a short 35 or 28mm lens. Best way to prevent it is to use a bigger hood.

Roland.

 

[coelacanth]

Hmmm. Thanks Roland. I guess I really need more testing. Since it's shown in the bottom corner, that is supposed to be upper edge of the camera either leakage or blockage is happening, right? I just can't see how anything can get in the way there, but of course I can't be 100% sure. Because the tone is a midway gray, I can't really tell if it's leakage (bright) or blockage (dark).

If anyone has an M without film loaded, could you please see if you'll see the slightest light coming through (seeing from backdoor open, curtains open) when you point an LED light super close to the top edge of the mount while a lens is attached? I had to test it in very dark room to see the slightest light coming through. If that's a normal behavior, I can at least eliminate that from potential cause list.

 

[ferider]

Only if the light leak is in the back, it will be in the upper left of the negative.

Since it comes from the front, it is happening on the lower right of the lens. For me it was a finger, accidentally and casually put there when carrying and shooting. Note that the shape of the blockage is different between first and second photo.

Roland.

 

[coelacanth]

Thanks again Roland.

I'm trying to think straight with this 5th grade physics right now while I'm at work, editing video footage for a tight deadline. 😛

The image is projected to the film surface upside down, right? So the bottom of the picture is actually at the upper side of the camera. Now, the leaked light is not traveling through the lens so it should be landing at the place where it's entering from: light coming in from upper side of mount, landing upper side of film surface in camera, shown at the bottom of picture??

I guess not smarter than fifth grader. 😛

 

[ferider]

You are right. If it's a leak behind the lens' nodal point its on the upper left. If it's your finger (in front of the node) its on the lower right 🙂 I guess not smarter than fifth grader. 🙂

Just hard to believe the mount leaks .... it's the highest precision mechanical piece of any camera. Hey, if we meet for beer and gear, you could try the same lens on one of my Ms and see if the same happens ?

 

[Tom A]

Also check that the "seal" around the rangefinder arm/coupling is not gone adrift. Try shining the LED through the finder (shield it with some paper wrapped around it) and look inside the shutter box. Put it on B and leave a lens or lenscap on. I had that problem with a couple of M6's long time ago.

 

[coelacanth]

Roland,

Hehe. I know I won't survive the Are You Smarter than a 5th Grader? show. Well, I probably won't even get a 2nd grade English right (I'm not a native English speaker to start with).

Anyway, your point still stands if that is indeed a finger. If the finger was getting in the way while I'm holding the camera like in my profile pic, the blockage IS traveling through the lens so it will end up upside down like the rest of the picture.

I just shot some test frames with my index finger intentionally set very close to the edge of the lens with a filter attached. I'll see if this reproduces the look when I develop the roll tonight.

And that would be great if you can let me test out your lenses on my MP when we meet up for a beer and gear.


Tom,

Thanks for the input. I'll try the LED light test against VF tonight. If the problem is indeed leakage, not blockage, that will definitely line up with the location of the leak.

 

[former member]

Well, the last person that was smarter than a 5th grader won the Nobel Prize.

Report back on the results. I've never seen a light leak through the lens mount before.

 

[coelacanth]

Will definitely report back. I am having hard time believing there is a leak from mount myself.

So far the only facts I know are

1. Very few pics got this leak-or-block at bottom right corner.

2. With an LED light test (intentionally pointing light super close to the mount), I DO see slightest light coming through around top edge of the mount.

I am not really sure if the fact #2 is actually a problem or it's way it is. I'll do some more LED test as Tom suggested (if this is the case, it's a leak but not from mount), and will develop test roll with my index finger held very close to lens' edge trying to reproduce the problem (blocking, me being wide angle noob). Also I'll try to see other lens/body combination with Roland's help at Bear & Gear meet (If this is the case, that's a leak from mount).

 

[35mmdelux]

This has happened to me when using new lenses or lenses without hoods. In my case, 24mm/CV, 21mm/CV, 35mm Canon Black, and 35 pre-asph Summilux. With a true light leak almost every frame would have the same damage configuration, not so here. Just a thought.

Often its simple pilot error. Anyhow go down the elimination list and lets us (me) know. Paul