Praktica BX20S light leak, B200 shutter speed issue

[Agulliver]

I thought I would start a specific thread rather than block the Praktica appreciation thread.

After flawless performance since new in 1993, my Praktica BX20S has developed a light leak. I have attached a couple of photos to give an example. It seems that the bottom of the frame is worse, suggesting the leak might be worse at the top of the film chamber if my understanding of optics is correct. The camera was fine up until March 2016, when I shot a roll of Ilford Delta 3200 without any issues. Then in May/June 2016 I shot a bulk rolled cassette of Fomapan 100 and a bought cassette of Acupan 100, with the same results. The light leak. Photos taken in a dark church were fine, so it's definitely a light leak.

I have since gaffa taped the brass clasps, and shot a quick test roll. The leak is still there. The foam around the window seems fine. Indeed I cannot see any problems. Does anyone have any ideas?

So I got out my B200, intending to use it instead. But despite the LED's functioning correctly and indicating the metered shutter speeds, the shutter is only firing at one speed. I am guessing approx 1/90s.

 

[cuthbert]

The solution for the light leak is simple: remake all the seals, kits online are cheap.

For the B200 it sounds like a cable that doesn't work or something like that, on the Praktica thread I posted a pic of a disassembled B, I assume the only thing to do is to open it and check cable by cable the shutter module.

 

[shutterfinger]

Does the over exposed band extend into the the rebate area of the film? Yes-light leak> probably the film window so block it. They are a common problem source.
No>shutter problem, probably needs a CLA.
B200 possibly need the shutter serviced also.

 

[cuthbert]

Does the over exposed band extend into the the rebate area of the film? Yes-light leak> probably the film window so block it. They are a common problem source.
No>shutter problem, probably needs a CLA.
B200 possibly need the shutter serviced also.

I see you are a competent guy in term of camera construction but I need to point out Prakticas Bs and Bxs have vertically traveling metal blades...I do NOT think they might create a vertical band, I assume it should be horizontal, am I wrong?

 

[shutterfinger]

yes it will be hard for a vertical travel fps to make a vertical strip over exposure.

 

[Agulliver]

The fogging is a vertical area which affects the entire film, as seen in the attached photo of a strip.

 

[cuthbert]

The fogging is a vertical area which affects the entire film, as seen in the attached photo of a strip.

Yup, light leak IMO.

but it looks like a problem when you were loading or unloading the camera, are you sure the cassette wasn't exposed to light? Is that the only film with the problem?

If the problem are the seals you can easily replace them, as an interim solution you may shoot with the camera in the half case, in many cases it helps.

 

[shutterfinger]

Does the over exposed band extend into the the rebate area of the film? Yes-light leak> probably the film window so block it.

Film window light leak.

 

[Agulliver]

It affected the most recent two films, one hand rolled and one with a regular bought cassette. Both were loaded in subdued light, as is my normal practise. I'm unable to identify anything unusual about the procedure, neither film was in the camera for long either. One roll was fresh, one was outdated but I've successfully used many rolls from the same batch.

The film window foam looks good, but I can quite easily try a quick test roll with something opaque stuck over the film window to see if it helps.

 

[shutterfinger]

Lay a strip of the light leak film in the camera with the top of the image at the bottom, emulsion facing the curtain, and the frame aligned on the curtain opening.
There are two possibilities for the leak, the film window and the back hinge. The pictures in the user manual looks like there is an overlapping metal flange light trap system in use at the back hinge and I doubt seriously the leak streak on the film ever lines up with the back hinge but the light leak streaks will align with the exit edge of the film cassette.

 

[Agulliver]

Shutterfinger, that's a very clever idea. On trying your suggestion, the light leak almost matches the hinge but it is a 100% match for the exit of the film cassette.#

My next step is going to be to cover the film window and shoot a few test frames while leaving the camera in the light somewhere...see if that solves it. If it is the film window I can repair the foam seals properly at a later date.

 

[Agulliver]

Just a quick update, with three layers of gaffa tape over the film window, and the camera left in direct sunlight for several hours, the result is no light fogging.

Many thanks, I've now been able to identify the source of the leak and affected a temporary solution. I can now replace the foam if I want something more elegant...but importantly my favourite camera is back in action.

 

[cuthbert]

Happy to hear the Bx is fine now, although not as good as a Nikon F2A or a Pentax LX it's a nicely spec'd camera that does everything fine and some of the lenses for it are the best in the business.

 

[Agulliver]

Indeed I seriously like the BX20s. I've got a B100, B200, BCA and MTL5 as well as Nikon F601M in the 35mm format (as well as some lesser non-SLR cameras) and it is by some margin my favourite.

Having been building up a collection of Praktica B mount lenses since 1990, I've got a good variety of Sigma, Carl Zeiss-Jena and of course some Tamron Adaptall lenses plus the requisite adapter. Even the Prakticar lenses are OK though the only one I really use is the 21mm.