Contax IIIA film advance question

[campy51]

I have a IIIA that when I put pressure on the take up spool and wind the shutter I can stop the spool from turning but the shutter still cocks and fires. Is this a safety mechanism or is it slipping? Also how do I check the opening between 1st and 2nd shutter?
Any help appreciated.

 

[dxqcanada]

It is supposed to slip.
The sprocket gear drives the film to the pickup ... the pickup slips because the circumference increases with more film.

I would suggest taking the camera apart to be able to work on the shutter.

 

[campy51]

I did take it apart but didn't remove the actual shutter. I cleaned and lubed some items. I haven't been getting consistent exposures so I assume the curtain openings are off. The speeds seem fine to the eye and ear but I don't know how 1/500 should look on focal shutters, I usually deal with leaf shutters.

 

[dxqcanada]

Ah, you have no timing measuring device?

 

[dxqcanada]

Richard Haw - Contax repair

 

[campy51]

Only have phone app but it's better used on a leaf shutter. What should it look like when looking through at light source? Should I see a complete circle looking from the film plane?

 

[dxqcanada]

The contax shutter operates as a variable slit ,,, both curtains move as one. The shutter speed dial sets the width of the slit.
Unlike a leaf shutter you will not see a complete circle as the slit is moving across the film plane.

 

[campy51]

The contax shutter operates as a variable slit ,,, both curtains move as one. The shutter speed dial sets the width of the slit.
Unlike a leaf shutter you will not see a complete circle as the slit is moving across the film plane.

Most of the time I see the whole circle when looking through the back with lens off. Does that mean I am overexposing? The 1/1250 is the only one I see a shading at the bottom and sometimes I see no light at all. I have looked through the back with the lens off and looked through the front with the lens off.

 

[dxqcanada]

Hmm, I should correct my last statement ... yeah if the shutter speed is low enough you your brain can process the light coming through the moving slit and see a circle.
You really need a device to measure the exposure.

 

[campy51]

I just discovered something using my iphone, I can do a slo-mo video and I can see the opening between the 1st and 2nd curtains. The high speeds are more blurry because of the speed but slower speeds look pretty good. Here are a couple of screen shots. The 2nd one is at 1/1250. Does it look normal?

 

[dxqcanada]

Hmm the curtains are not parallel the film gate opening ... so I am guessing a problem with curtain strap on the left ... it is not traveling downwards properly.

 

[campy51]

Wouldn't it be fine as long as the opening is the same as far as exposure? The opening looks parallel to me.

 

[dxqcanada]

Hmm, could be rolling shutter effect as it looks like the left side of the shutter is higher.

 

[campy51]

I'm going to start a new thread with just this subject.