Miranda Sensorex (Shutter Capping or Sluggish Mirror issue)

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noahsmith

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Hi Everyone,

I'm having either a shutter capping or sluggish mirror issue with my Miranda Sensorex (No. 910444). I originally posted about this problem here. The community has been very helpful in trying to diagnose the issue, especially David Lyga - thanks a lot! Basically, a lot of my photos come back with half or even all of the photo black, which lead me to thinking it could be a shutter capping issue. After some tests though, I'm still trying to confirm if it's the shutter curtain or the mirror thats causing the issue.
As I have still not been able to fix the issue after a lot of trial and error, I thought I would post about it on here and see if anyone has any suggestions. Feel free to look at the original post to get a little more context, I'm going to include relevant links below:
  • Here's a video of the camera with the back open facing a white light, testing speeds from Bulb to 1/1000s:


  • Here is a video of what the shutter curtain looks like at 1/60s:
    https://photos.app.goo.gl/vzQdcZEithVUdCgk6
    It seems like the curtain moving from right to left is a little slow. This doesn't happen everytime, it was sporadic.

  • Here is a video of what the shutter curtain looks like at 1/500s:
    https://photos.app.goo.gl/CnDTEfjvA6twy7j3A
    It looks like at this speed, the curtain moving from left to right is slow. This was also happening sporadic.
I also taped up the mirror and filmed what the shutter curtain looks like in slow motion, here are the results:
If you have any suggestions, it would be much appreciated, thanks a lot.

IMG_7331.jpg
 

shutterfinger

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Its your shutter. It needs to be disassembled, cleaned, lubed, reassembled, and adjusted.
Starting at second 22 in your video of speeds from 1 second up the second curtain bottom exceeds the top by a significant amount and becomes more pronounced as the speeds start to increase.
It may be debris in the track between the two curtains affecting only the second curtain or the bottom of curtain 2 is releasing prematurely.
 
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noahsmith

noahsmith

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I just did a test where I put the Miranda facing downwards (with the back open and a light source facing the back) on top of my DSLR's lens and fired the shutter on the Miranda from 1s-1/500s, photo below for reference. I set my DSLR to a shutter speed of 3 seconds so I could first fire the DSLR, then fire my Miranda's shutter. I took a photo with the DSLR each time and did not see anything covering the area where the shutter opens or anything getting in the way of the image. Thoughts?
 

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noahsmith

noahsmith

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You are chasing your tail.
CLA the shutter.
Screen shot of your first video.
View attachment 209763
Only a malfunctioning shutter will produce a diagonal across the image plane.

Yeah, whenever I move the shutters manually though from their center point, they appear perfectly straight. So I'm not sure how they are showing up diagonally.

Also, I noticed the aperture blades have some oil around them and when shooting at higher speeds, it stays wide open and never closes down to the correct aperture. So I'm taking the lens apart and will clean it up.
 

shutterfinger

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I had to download your video and play it back at slow speed to capture these screen shots. The shutter is inconsistent. Sometimes its the first curtain other times the second while others may be both.
ScreenHunter_37 Oct. 18 16.04.jpg ScreenHunter_38 Oct. 18 16.05.jpg ScreenHunter_41 Oct. 18 16.05.jpg ScreenHunter_43 Oct. 18 16.07.jpg
The third is when the shutter is open at 1/60 or slower. The frame edge should always be perpendicular to the film rails.
The curtains are on spools with bearings on each end with a spring in the center. The bearings on the spools are not moving smoothly.
If the aperture is oily it too needs cleaning.
Take a look at post 17 in https://www.photrio.com/forum/threads/zorki-6-curtain-adjustment.161638/ to see what a horizontal travel focal plane shutter looks like removed from the camera.
 

Theo Sulphate

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Yeah, whenever I move the shutters manually though from their center point, they appear perfectly straight. So I'm not sure how they are showing up diagonally.
...

What type of camera are you using to produce the video? Unless what constitutes a video "frame" is exposed all at once, you'll get a diagonal image from any moving object. That is, if the top of your video frame is exposed at a different instant in time than the bottom, then any moving object will appear elongated in a diagonal manner.

Classic example is the photo of the race car where the wheels appear elliptical because the focal plane shutter of the camera exposed different parts of the frame at different points in time as the car moved.
 

shutterfinger

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Classic example is the photo of the race car where the wheels appear elliptical because the focal plane shutter of the camera exposed different parts of the frame at different points in time as the car moved.
That classic image was made with a large format camera with a fixed slit in the curtain that ran from top to bottom of the frame. Such focal plane shutters take 55 milliseconds to 45 milliseconds to travel the 4 inch dimension in landscape position of a 4x5 frame. If such was the case with video cameras one would see such diagonals in moving objects of all types in videos.
Standard Video is 24 fps, fewer fps produces fast movement such as early silent films while more fps produces slow motion provided it is played back at the speed it was recorded at.
 
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