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Hmmm.. Focal Plane Shutter

 
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peter k



Joined: 26 Dec 2009
Posts: 166
Location: Sedona Az

PostPosted: Tue Dec 13, 2011 2:56 am    Post subject: Hmmm.. Focal Plane Shutter Reply with quote

Can the Focal Plane Shutter, if not 'locked' cause a smaller area of the negative to be exposed? I have four negatives, that the long side, away from the film notch, gradually gets larger, with less area exposed.

I believe this has to be it, because I remember trying to focus off the ground glass and had to reset it wide open, and I 'think' it was after these four shots that where made at the same time. It must have gotten unlocked.

BTW.. Why, or when, would you use the Focal Plane Shutter, rather than the front shutter?
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Dan Fromm



Joined: 14 May 2001
Posts: 1881
Location: New Jersey

PostPosted: Tue Dec 13, 2011 11:30 am    Post subject: Re: Hmmm.. Focal Plane Shutter Reply with quote

peter k wrote:
BTW.. Why, or when, would you use the Focal Plane Shutter, rather than the front shutter?


To time exposure when using a lens in barrel.

To get a higher shutter speed than a leaf shutter can give.
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45PSS



Joined: 28 Sep 2001
Posts: 3196
Location: Mid Peninsula, Ca.

PostPosted: Tue Dec 13, 2011 7:59 pm    Post subject: Reply with quote

A FPS when wound to any aperture has the light path blocked until the shutter is tripped then the aperture opening moves over the film area leaving the light path from the lens blocked again. When wound to the "O" position the light path is blocked until the shutter is tripped then the "O" slot which is larger than the film plane moves to the film plane opening the light path from the lens fully.

Only a malfunction FPS could hang the shutter curtain so that it partially opened the light path or something jammed the wind key preventing it from turning.

Open the view hood and remove the film holder. Open the lens shutter and set its aperture to wide open. Run the FPS down fully then set the tension to 1. Wind the FPS until the "O" slot is over the film plane and you can see through the lens.
Trip the FPS and verify that the curtain closes fully and locks (the wind key will only turn in the direction of the wind arrow). If it does not the shutter needs servicing.
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peter k



Joined: 26 Dec 2009
Posts: 166
Location: Sedona Az

PostPosted: Sat Dec 17, 2011 1:30 am    Post subject: Reply with quote

OK...

It closes, but not with a snap, more like a 'quick' curtain... Correct?

The tension lowest number is One. That's all mine will go to when I increase it to two or three, and then release its 'lock', it goes to One.
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45PSS



Joined: 28 Sep 2001
Posts: 3196
Location: Mid Peninsula, Ca.

PostPosted: Sat Dec 17, 2011 2:05 am    Post subject: Reply with quote

Sounds like the shutter is working correctly.

Quote:
Can the Focal Plane Shutter, if not 'locked' cause a smaller area of the negative to be exposed? I have four negatives, that the long side, away from the film notch, gradually gets larger, with less area exposed.



What focal length lens was in use?

Remove the lens board with the bellows extended as they were in the bad exposures. Look through the camera from the view panel. Anything, such as a sagging bellows in the light path?

Remember that the image on the film is upside down and reversed. Hold the negative with the emulsion away from you and the top of the scene at the bottom. The low/unexposed edge should match the side of the camera where the flaw occurred. If the FPS had hung with the O aperture not fully over the film opening it would have blocked a strip on the edge of the film, top or bottom, depending on the position it hung in.

Low exposure=film base + fog + weak, faint image that scans/prints black.
Over/high exposure=film base + fog + very dense area that scans/prints white/light.
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peter k



Joined: 26 Dec 2009
Posts: 166
Location: Sedona Az

PostPosted: Sat Dec 17, 2011 2:48 am    Post subject: Reply with quote

Quote:
What focal length lens was in use?

as in 135mm Graflex Optar f4.7 ?

Quote:
If the FPS had hung with the O aperture not fully over the film opening it would have blocked a strip on the edge of the film, top or bottom, depending on the position it hung in.


It was the top edge.

A couple of days ago, I developed 8 more shots .. 1 through 4 (no problem) where before the group that I had trouble with, 5 & 6 where shot at the same time and show the same problem, and 7 & 8 after I re-cocked the FPS, also showed no problem. .

After I posted this originally post, that I dug out the Instruction Manual and looked it up, and discovered that I had the shutter lock 'off' not on. This may have been the cause of the problem. Now I have the lock pushed in the correct direction and have tested it.
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45PSS



Joined: 28 Sep 2001
Posts: 3196
Location: Mid Peninsula, Ca.

PostPosted: Sat Dec 17, 2011 4:13 am    Post subject: Reply with quote

I was not familiar with the shutter lock so I took a look at the instruction manual. The lock prevents accidental tripping of the shutter. The lock automatically releases when the wind key is turned either by winding or , I assume, manually operating the M lever.

Try packing the curtain. To pack a curtain set the tension to 6 then wind the curtain to the 1/8 aperture (D) and run down to closed after O 10 times in succession. Once packed the curtain will loosen with normal use. If packed then locked on O it should stay packed if it is not used. Return the tension to 1 when finished or when storing. Storing with the curtain at O and tension 1 is OK. The difference between closed after O and O on the tension roller is 2 turns of the tension set screw.
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peter k



Joined: 26 Dec 2009
Posts: 166
Location: Sedona Az

PostPosted: Mon Dec 19, 2011 1:52 pm    Post subject: Reply with quote

Boy... I bet that curtain hasn't been packed in a long time... but the springs are still good, and the curtain moves faster now, not that I think I'll ever use it, but who knows.
With this and setting the lock, I sure there will be no more problem.

thanks..
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troublemaker



Joined: 24 Nov 2003
Posts: 715
Location: So Cal

PostPosted: Fri Jan 20, 2012 6:01 am    Post subject: Reply with quote

Focal plane shutters tend to be far more accurate than most vintage leaf shutters. I've done plenty of comparisons and shutter speed testing. A leaf shutter can easily be more than a stop slow in the faster speeds whereas a poorly running FPS can be within a 1/3 stop at it's higher to mid speeds completely ruining any misconceptions one might have about these antique wind up roller curtains. All of my opperational FPS shutters perform better at all speeds than most of my good running front leaf shutters, hands down. As for the B and T settings use, I tend to shy away from these with the rollers as this requires I stress the old roller springs so that they will close the shutter completely when I shut it down, but I've used them in this capacity at times with excellent results.
Why do you think so many high quality 35mm camera bodies have focal plane shutters in them rather than junky front leaf types? Do you think it has anything to do with accuracy, even light across the film plane, or what ? You have some research to do. Then think about the mechanical action of opening and closing those leaves compared to the smooth and simple opperation of a curtain aperture passing evenly over the film pane expaosing the film to equal amounts of light. Play around with a shutter tester and a box full of vintage lenses sometime and then test a few focal plane shutters that sort of work. The focal plane shutters will ususally blow away the leaf shutters, even if all those leaf shutters are recently serviced. Did I make my point?
I like and prefer leaf shutters for long exposures when I do my own timing, and of course when I am hiking and do not wish to carry a Speed with the heavy extra weight of the FPS. But I have never got better exposures than when I have used the FPS at the available speeds it offers. Get it working properly and start using it.
SA
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