Solving Travis's streak problem

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I am repeating my reply here because I have had this problem with more than 1 Leica body. I think it is another important Leica problem that should be known. Specially if you are testing to buy a new or second hand body. The problem is streaks parallel to the long side of film manifesting themselves mainly at 1/1000 sec (sometimes at 1/500), and specially noticable when you have an even subject matter like blue sky. "Travis, I know exactly what the problem is, because I have had it too in exactly the same place. It happens when the edge of one of the blinds (the metal strips) is not absolutely straight and smooth up and down. It happens mainly at 1/1000 and sometimes at 1/500 depending on subject matter. At 1/1000 the shutter slit is very narrow, and where there is any imperfection on the metal edges (e,g. like a pimple sticking out) that spot causes slightly less exposure at that height on the film. As the shutter travels across the film this manifests it self as a darker (less exposed) strip on the film. At slower speeds the shutter slit is wider, so the proportion of the "pimple" to the size of the slit is much smaller, so it does not show itself as an exposure difference. The fact that streaks are strong on one side and they dissapear towards the other is because your slit is uneven from left to right. I f you make tests you will probably find that at 1/1000 one side of your frame is darker than the other side due to unequal shutter blind travek speeds. If all this does not make sense, get in touch with me. "

-- sait (akkirman@clear.net.nz), May 10, 2002

Answers

Seems to me since the shutter travels horizonatally in the M that a "pimple" on the side of one of the curtains would create a horizontal streak on the film, not the vertical streaking Travis had...

-- Jack Flesher (jbflesher@msn.com), May 10, 2002.

The example that Travis provided was from the camera being held to do a portrait format shot. The streaks are horizontal in the frame.

/r

-- Randy Samos (samos@lensman.net), May 10, 2002.


Thanks Randy.

-- sait (akkirman@clear.net.nz), May 11, 2002.

You're welcome Sait.

Earlier on in this thread, I was trying to say what you just did, but had to speak from lack of experience. I've seen/heard of this problem LOTS of times with Horizon panoramic cameras, but I had expected the machining on the Leica shutter to be a large cut above that little overrated gem.

I'm a bit dissapointed to find out I was wrong in that assumption. :(

/r

-- Randy Samos (samos@lensman.net), May 11, 2002.


Thx Sait.

Jack, the streaks run PARALLEL to the length of film in all problem pics. So, the BUMP ON SHUTTER EDGE theory HOLDS.

Just to clarify that I understood what Michael, Randy and Sait said earlier in my thread

I believe that if there is a BUMP on the upper shutter edge of one of the curtain cloth, then as the shutter slit travels across the film, the track of streaks will be formed in line with where the BUMP spot is, BECOS LIGHT WILL BE BLOCKED. aM i RIGHT?

SO, according to my pics, I think there are a FEW BUMPS on the upper edge.

I hope i know what I just said!;))

-- Travis (teckyy@hotmail.com), May 11, 2002.



Question is, if there are BUMPS, how do I pry open the two shutter and then smoothen the edges???

damn.;)

-- Travis (teckyy@hotmail.com), May 11, 2002.


Sait, I seriously think you have gotten the REASON for the streak problem. How did you learn of this, and what did u do to correct it?

It seems very logical, the bump/pimple theory.

Randy, credit goes to u too! Brilliant.

-- Travis (teckyy@hotmail.com), May 11, 2002.


Travis, when the problem shows at the top of the neg, (don't forget that the film is travelling upside down in the gate), you really have to look at the lower portions of your curtains. If the problem is on the following curtain edge it is easy to check - you turn the speed to "B" setting, without a lens on the body, push the button to let the first curtain go then put a pencil, or similar thing into the open gate and let the second curtain loose and let it settle against the pencil. Now look at the edge from both the back and the lens sides of the camera with a magnifier to find the imperfections. (I do not accept any responsibility for this suggestion if anything goes wrong). If the problem is on the first curtain then I am afraid it is a repair persons to dismantle the whole thing and check the curtain edge. The repair has been done successfully on my particular camera.

-- sait (akkirman@clear.net.nz), May 12, 2002.

Repair should be done by someone qualified. Settling for a lower 1/1000 actual speed (eg 1/700) might also ease the problem as the slit then will be wider.......

-- sait (akkirman@clear.net.nz), May 12, 2002.

Sait, got it.

Thx for finally solving the mystery.

Really appreciate it.;)

At least I know now why I had to part with it.

-- Travis (teckyy@hotmail.com), May 12, 2002.



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