Diagnosis, please: Leak / shutter prob. w/ Spotmatic

[wwfloyd]

Please help me pinpoint my issue with a Pentax Spotmatic. I get a very subtle, white, vertical streak from the top of frame, down about 1/3 of the way or so. It's always in the same position, when I can see it (sometimes it's not there, or very well hidden).

I am including a composite photo that shows the effect in 2 frames, with red arrows near the bottom of the fault. For comparison, I have also included a frame from a K1000 with laggy shutter curtain... noting there, that the fault goes all the way down the frame, and its location varies from shot to shot. This difference makes me doubt that the Spotmatic has a shutter fault.


EDIT: It shows on the negs, so, not a scanner issue.

https://www.flickr.com/photos/wwfloyd/47925289138/in/dateposted-friend/

 

[Steve M.]

Your negative will tell you whether it's a camera issue or the scanner. Unfortunately, these cameras are known for shutter issues, and often need a good CLA to get things going. The shutters tend to get gummed up from deteriorating mirror foam I believe.

 

[retinax]

This is the first time I hear spotmatics were known for shutter issues. But yours looks like one. If the line is visible outside the frame, it's a light leak, if not, a shutter issue. If the transition is from one pixel to the next in the scna, it's a scanner issue.

 

[aizan]

the shutter is capping, with the second curtain abruptly hitting a snag rather than changing speed gradually. it's not a problem specific to spotmatics or related to mirror dampening foam. it's just routine maintenance.

 

[Sarcophilus Harrisii]

the shutter is capping, with the second curtain abruptly hitting a snag rather than changing speed gradually. it's not a problem specific to spotmatics or related to mirror dampening foam. it's just routine maintenance.

The Spotmatic shutter, like almost every other focal plane shutter made in the last eighty years is "self-capping". Meaning one does not need to cap the lens when winding on the film and cocking the shutter.

If this one was "capping" during the exposure cycle, then, there would be no exposure at all on a part of the neg. Some tapering, perhaps. It seems to have a running inconsistency, if there are no light leaks occurring.

 

[wwfloyd]

OK, I have verified that the streaks do not extend beyond the frame on the negs, so, not a rear light leak. Not a scanner issue -- I wasn't thinking, on that point.

As far as shutter fault, what I don't get, is, why does it not extend down the entire frame, as with the 3rd example, from the K1000? Are we thinking the Spotmatic has a slight angle to the edge of the shutter curtain, and that it has early onset of the same fault the K1000 has?

Is there nothing unusual that could be happening in the mirror box that could put that little touch of extra light there?

 

[aizan]

AFAIK, capping is synonymous with tapering. Is a "self-capping" shutter a term from the 19th century?

 

[retinax]

OK, I have verified that the streaks do not extend beyond the frame on the negs, so, not a rear light leak. Not a scanner issue -- I wasn't thinking, on that point.

As far as shutter fault, what I don't get, is, why does it not extend down the entire frame, as with the 3rd example, from the K1000? Are we thinking the Spotmatic has a slight angle to the edge of the shutter curtain, and that it has early onset of the same fault the K1000 has?

Is there nothing unusual that could be happening in the mirror box that could put that little touch of extra light there?

You're right, that is very strange. Both the pictures you show have a very bright bottom foreground, on the side opposite of the streak. It might be a reflection from something in the mirror box. Is there anything reflective in the mirror box or the back of the lens?

AFAIK, capping is synonymous with tapering. Is a "self-capping" shutter a term from the 19th century?

I've probably only read about this on this very forum, and think the terms weren't used interchangeably, and it makes a lot more sense to stick with the original meaning so we're able to distinguish the two faults, even if one could see capping as the most extreme case of tapering.

 

[Sarcophilus Harrisii]

AFAIK, capping is synonymous with tapering. Is a "self-capping" shutter a term from the 19th century?

No, tapering exposure can be an issue with or without the second curtain capping the exposure prematurely. If a particular shutter is in need of service it's not at all unknown for certain speeds, say middle speeds, 1/125 to 1/500, for example, to manifest tapering of the exposure across the film gate, whilst 1/1000 (or if the mechanism is badly in need of service even 1/500 or longer times) to only expose a portion of the gate (or even no exposure at all if the first curtain is dragging severely). The narrower the slit width, the more readily capping might occur with an old shutter that needs some work. Capping will often be preceded by some degree of tapering exposure because what is happening if a shutter "caps" is the second curtain prematurely catches the first. Unless a first curtain is dragging so severely that the laths never properly separate (no exposure anywhere, the curtains run across the gate closed) there will usually have to be some band of reducing exposure up until the second curtain lath actually touches the first, and blocks the light ("caps").

My reference to "self-capping" was to demonstrate what the term "capping"' actually means. That it is taken for granted in modern times a focal plane shutter will automatically shield the film from light whilst being cocked, does not invalidate the term as an accurate description of shutter operation.
Cheers,
Brett

 

[wwfloyd]

You're right, that is very strange. Both the pictures you show have a very bright bottom foreground, on the side opposite of the streak. It might be a reflection from something in the mirror box. Is there anything reflective in the mirror box or the back of the lens?

No, it's all very normal in appearance.

 

[julio1fer]

Probable shutter problem.

Send it for a CLA. Spotmatics were made to last but they need a bit of maintenance every few decades.

 

[aizan]

so a shutter that is capping, in the original sense of the word, is operating normally? and it only refers to the operation of a shutter as it is being cocked by the advance lever?

but in the more modern sense of the term, capping is a more severe form of tapering, with the main difference being that capping causes part of the film to be unexposed, while tapering only reduces but does not totally prevent exposure? are the causes and repair of the two malfunctions the same?

 

[retinax]

so a shutter that is capping, in the original sense of the word, is operating normally? and it only refers to the operation of a shutter as it is being cocked by the advance lever?

but in the more modern sense of the term, capping is a more severe form of tapering, with the main difference being that capping causes part of the film to be unexposed, while tapering only reduces but does not totally prevent exposure? are the causes and repair of the two malfunctions the same?

Capping means there is no slit between the curtains as they move across the film gate. This is desired while the shutter is being wound and undesirable when an exposure is supposed to happen, and it has been this way ever since focal plane shutters were first made.
When tapering is very strong, the shutter can be capped for part of the exposure.
Does this help clearing up the nomenclature?
As for causes, there is an overlap- if the second curtain is faster than the first, one has tapering that in extreme cases/at fast settings can become capping. If the second curtain is slower than the first, tapering but no capping. AFAIK there can be some other causes for capping as well, depending on the construction of the shutter.

 

[Sarcophilus Harrisii]

Capping means there is no slit between the curtains as they move across the film gate. This is desired while the shutter is being wound and undesirable when an exposure is supposed to happen, and it has been this way ever since focal plane shutters were first made.
When tapering is very strong, the shutter can be capped for part of the exposure.
Does this help clearing up the nomenclature?
As for causes, there is an overlap- if the second curtain is faster than the first, one has tapering that in extreme cases/at fast settings can become capping. If the second curtain is slower than the first, tapering but no capping. AFAIK there can be some other causes for capping as well, depending on the construction of the shutter.

Helpful explanation, thank you. May I clarify, though, that some early focal plane shutters, (particularly certain large format types which necessitated the selection of one of several pre-formed slits, in order to facilitate the various speeds available), were not self capping. The photographer would need to actually place a lens cap over the lens during the cocking cycle, to prevent fogging of the film or plate.

Also, as I mentioned earlier, if a particular shutter is badly in need of service and/or replacement curtains, it can happen that if the first blind is dragging badly enough, both curtains may run across the whole film gate with their laths already adjoined—Ie no exposure whatsoever—completely capped. I've certainly seen this on several occasions, although admittedly the cameras involved usually had very old, stiff curtains that substantially exacerbated problems resulting from any need to service the actual mechanisms. A pre-war Kine Exakta I have (which probably still has its ancient original curtains) may be doing just that on some of its speeds, although as it's been a while since I've fired it I'd have to check it to be sure.
Cheers
Brett