Pentax 6x7 experts please advise

[chris77]

hello forum
Please help me out with these horizontal streaks and this strange vertical line on ly negatives
It didnt only happen on this roll.
Here i tested a lens so the shots are quite random but there is sky and thats where the problem is visible.
I guess its related to the shutter curtain, research online shows that in the early 6x7s shutter curtains get sometimes dirty with sticky stuff, but how would it make such streaks??
Camera used is pentax 6x7 MLU version
Can i fix it, got some skill but not like a camera repairman.
Cheers,
Chris

 

[Lachlan Young]

Those are almost certainly process related streaks, not camera related problems.

What's the film?

 

[chris77]

Those are almost certainly process related streaks, not camera related problems.

What's the film?

This is fomapan 100
It also happened with fomapan 200
Rod 1+50 7min 1min constant then 4 twirls/min

Look at the position of the streaks, (the two tree shots happened within a few seconds) the streaks are in the same place... but one one there is a huge vertical line aswell..

 

[chris77]

I forgot to mention..
some time ago i had the same camera shoot blank frames from time to time (only when using fast shutter speeds it seems)
but as this problem disappeared since i give the camera a few seconds between shots and fresh batteries, i didnt think about problems with the shutter anymore..
until recently..

 

[Dan Daniel]

The horizontal streaks are processing issues. Is this development tank and method new to you or something that you've had success with in the past?

The dark vertical band could be a shutter stutter? Something like this but in the middle, not a bounce? The curtains hanging up in the middle of the frame, the second curtain catching up and reducing exposure in sections? When you get to higher speeds, the two curtains don't leave a full opening across the whole frame, but create slit that travels across the frame.

 

[chris77]

tx for your reply.
i have developed hundreds of rolls in this tank, 35 and mostly 120
its not a minimal agitation scheme.
i will try a roll of acros tomorrow against a wight wall and post the results.
this never happened with the mamiya rz67

ps. shutter speed of the shot with the vertiacal line was 1/60

 

[Lachlan Young]

This is fomapan 100
It also happened with fomapan 200
Rod 1+50 7min 1min constant then 4 twirls/min

Look at the position of the streaks, (the two tree shots happened within a few seconds) the streaks are in the same place... but one one there is a huge vertical line aswell..

If it was a shutter issue it would be towards the ends of the frames and perpendicular (shutter bounce is the main fault with the big Pentax shutter) - I think the problems there are drying issues (humidity too low or heat too high) - they can be quite odd and partial - if you can look at the emulsion side of the film under a glancing light between the frames you can often just about see evidence of them. Alternatively it's a flow issue from the 'twirl' agitation - manual agitation of small tanks should involve fully and decisively upending the tank rather than some sort of gentle swirl. Rodinal is quite sensitive to bad/ indecisive agitation - at least that's what I've found.

 

[chris77]

If it was a shutter issue it would be towards the ends of the frames and perpendicular (shutter bounce is the main fault with the big Pentax shutter) - I think the problems there are drying issues (humidity too low or heat too high) - they can be quite odd and partial - if you can look at the emulsion side of the film under a glancing light between the frames you can often just about see evidence of them. Alternatively it's a flow issue from the 'twirl' agitation - manual agitation of small tanks should involve fully and decisively upending the tank rather than some sort of gentle swirl. Rodinal is quite sensitive to bad/ indecisive agitation - at least that's what I've found.

thats interesting, thanks!
humidity is in fact very low.
i will shoot another roll of the same batch and develop by inversion.
then report back tomorrow.

 

[Lachlan Young]

thats interesting, thanks!
humidity is in fact very low.
i will shoot another roll of the same batch and develop by inversion.
then report back tomorrow.

aha - low humidity at the drying stage is the most likely culprit - do you use a fan driven/ heated air drying cabinet or similar?

What I've found is that if humidity is low, you should almost never add any heat to the airflow - unless the ambient is really cold. Otherwise you can get these awkward interlayer drying marks. If your film is taking less than 15-20 mins to dry fully, that's usually an indicator that you may be at risk of those sort of marks.

 

[chris77]

aha - low humidity at the drying stage is the most likely culprit - do you use a fan driven/ heated air drying cabinet or similar?

What I've found is that if humidity is low, you should almost never add any heat to the airflow - unless the ambient is really cold. Otherwise you can get these awkward interlayer drying marks. If your film is taking less than 15-20 mins to dry fully, that's usually an indicator that you may be at risk of those sort of marks.

Well no, its 35-40 percent humidity with 20 degrees celsius. Shouldnt be an issue i guess..

 

[Lachlan Young]

Well no, its 35-40 percent humidity with 20 degrees celsius. Shouldnt be an issue i guess..

That's exactly the range where I've seen the phenomenon pop up intermittently - some emulsions are much more prone to it than others. Good air movement with no added heat (& wetting agent/ thorough squeegeeing of film) resolved it.

 

[chris77]

That's exactly the range where I've seen the phenomenon pop up intermittently - some emulsions are much more prone to it than others. Good air movement with no added heat (& wetting agent/ thorough squeegeeing of film) resolved it.

Hello again.
Did some extended tests.

It seems that a twirling agitation using the small paterson tank to develop one roll of 120 fomapan 100 in 1+50 rodinal, with continuous twirls for one min, followed by four twirls/minute for a total of 7:30 results in horizontal streaks as shown in my original post.
Developping the same way by inverting the tank has solved this and resulted in uniform negatives.

BUT, i have found another issue.
The 1/500 and 1/1000 dont give correct exposure.
Very faint if any on 1/500 , completely blank on 1/1000

Seems like shutter curtains out of sync?
Why doesnt it show at lower speeds?
Battery is alkaline but brandnew.

Can this be easily fixed or does it require CLA?
And if so, can you recommend someone not too expensive in western europe?

Thank you
Chris

 

[chris77]

well, i did a google search...
it doesnt look like there is an easy chance to fix this at home.
just in case somebody has a solution, please let me know.
in the meantime i will be looking for another body
cheers
chris

 

[Lachlan Young]

@chris77 good to hear that the streaks have been dealt with.

Regarding the shutter issue, there should be someone in Paris who can do a good repair on Pentax 67's - from what I understand of the shutter from a local-ish technician here, it's more or less an electromechanical device rather than fully electronic - and there is quite a lot that can be repaired/ cleaned before it would progress as far as needing a new shutter unit.

 

[chris77]

@chris77 good to hear that the streaks have been dealt with.

Regarding the shutter issue, there should be someone in Paris who can do a good repair on Pentax 67's - from what I understand of the shutter from a local-ish technician here, it's more or less an electromechanical device rather than fully electronic - and there is quite a lot that can be repaired/ cleaned before it would progress as far as needing a new shutter unit.

Thanks Lachlan.
I will check and have someone look at it if its affordable..
Kind regards
Chris