Uneven Exposure Problem (M6 Classic)

[atufte]

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Just had my images scanned and found an uneven exposure on the horizontal top of all my images (see the darker area/streak on top) this is with a "brand new" Leica M6 which i just bought, it looked totally unused, and that is probably also the problem (those bloody collectors should start using their equipment, not collect them to death... :-)

 

This is from two different films, one Tri-x and one Arista Premium, developed separately in a ATL-1500 which has worked flawlessly for a long time... (and i know it's not the scanner since i can see it with my naked eye when pulling down the exposure on the contact sheets, see ref)

 

(The levels are pulled down on these images to see the problem better, but it's also evident on a right straight level print, so it definitely needs a fix)

 

Thankfully i got two M6's so i'm not totally screwed, but i would like to know if this is a fixable DIY

since i have all the right Leica service tools myself (adjust shutter or whatever is needed)...?

 

Thanks in advance for any help...!

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Edited February 15, 2009 by atufte

[rob_x2004]

Left over right, right over left. Socks go on first.

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[robertwright]

if you are suggesting agitation, I am not sure.

 

my m6 had a funky shutter too. DAG suggested that if there is any unevenness on the leading/trailing edge of the shutter curtain, at higher speeds where there is only really a very small slit traveling across the film plane, the exposure will be affected. A bump would cause under exposure.

 

He said the width of the slit at 1/1000 was 1/8th of an inch or so, so it is finicky.

 

this is the price for a low-speed quiet shutter.

 

just a possibility.

 

we like to think of Leica's as reliable and on the whole they are, but as far a maintaining tolerances they are very poor. A cheap point and shoot has a more reliable shutter in terms of repeatability imo.

[atufte]

Left over right, right over left. Socks go on first.

 

I used a Jobo ATL-1500 so if it's agitation you are suggesting, that's not it, rotary process

is known to be very precise... but thx anyway

[newsgrunt]

I take it you've processed 35 with the Jobo previously ? Wondering if changing the speed might help although not sure how that would lead to the uneven horizontal areas of exposure. Possible that at fast speeds, the chemistry concentrates in the centre of the reel, if you follow. A stretch of course but tossing ideas out there. Can't see it being the camera since the shutter moves lengthwise across the frame.

 

I've only processed sheet film through my Jobo, no 120 or 35 though.

[earleygallery]

I doubt it's a fault with the camera. If the shutter was faulty you would (normally) see a lighter band at one end of the neg, running vertically. If it was an exposure fault it would be even over the negative of course.

 

It points to an issue with the development.

[atufte]

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I take it you've processed 35 with the Jobo previously ? Wondering if changing the speed might help although not sure how that would lead to the uneven horizontal areas of exposure. Possible that at fast speeds, the chemistry concentrates in the centre of the reel, if you follow. A stretch of course but tossing ideas out there. Can't see it being the camera since the shutter moves lengthwise across the frame.

 

I've only processed sheet film through my Jobo, no 120 or 35 though.

 

Jupp, i have developed a lot of films through the Jobo, all with prefect results, so i cant see

this as the problem source... And it's not possible to change rotary speed on the Jobo

if that's what you mean...?

 

What's even stranger, is that this only happens on some frames of the film roll (the ones taken

outside in bright light) and that really leaves out the development part as the problem source, and

brings back in the camera sealing/pressure plate/bottom plate as the only source...

 

I will try to use black tape on the back, and bottom to see if there is any difference....

 

Thx for your suggestion, and please do not hesitate with alternative solutions

[lincoln_m]

I am with Robert on it being some muck or bump on the shutter curtain. I had a similar issue with high shutter speeds. Regards Lincoln

[atufte]

I am with Robert on it being some muck or bump on the shutter curtain. I had a similar issue with high shutter speeds. Regards Lincoln

 

Ok thx, is there anyway to fix this DIY....? (i live in Norway, and would be very happy if i did not have to send it to Germany or even worse USA)

[newsgrunt]

Jupp, i have developed a lot of films through the Jobo, all with prefect results, so i cant see

this as the problem source... And it's not possible to change rotary speed on the Jobo

if that's what you mean...?

 

I have the CPP-2 which has adjustable speed control depending on what size drum one is using etc.. Is the ATL is an automatic one that does it all except dry ?

 

 

What's even stranger, is that this only happens on some frames of the film roll (the ones taken

outside in bright light) and that really leaves out the development part as the problem source, and

brings back in the camera sealing/pressure plate/bottom plate as the only source...

 

I will try to use black tape on the back, and bottom to see if there is any difference....

 

If you're not experiencing this on the whole roll then it does leave the camera as the primary concern.

 

What's also strange is that in the large example posted, you can see similar dark areas on the left side and a bit on the right. I can't see how a back could lead to these issues since the delineation is very gradual whereas a light leak would probably leave more distinct edges from light to dark.

 

Is it outside the realm of possibility that this could be lens related ? Again, stab in the dark. Good luck in your search for an answer and let us know when you find one.

[robertwright]

Ok thx, is there anyway to fix this DIY....? (i live in Norway, and would be very happy if i did not have to send it to Germany or even worse USA)

 

I chased a similar ghost for a year before DAG suggested the shutter.

 

the fact that you say it is outdoors at high speed makes me more suspicious.

 

He said on older cameras like the m2 with the rubber curtain the curtain end was crimped around the rubber (something like that, can't recall) and sometimes squeezed through the curtain end creating bumps, which is how he saw it once. The M6 curtain is not 100% straight edge like the metal blades of modern shutters. It is a fold over of thicker bent metal. When you look at it it is not a knife edge, it is more three dimensional. Any, ANY, irregularities on the edge will produce exposure differences when the shutter is high and the slit is small.

 

My ghost was a similar dark streak across the same place. Thinner. Always in skies! impossible to hide. Makes me think it could have been elsewhere but we don't hold the camera upside down!

 

As far as a fix I would email Don. Not sure what he would recommend. Get some ND:D! shoot at 1/60th!

[robertwright]

Ok thx, is there anyway to fix this DIY....? (i live in Norway, and would be very happy if i did not have to send it to Germany or even worse USA)

 

:ptrade for M7?

 

perhaps polishing the end of the curtain with some crocus cloth might help. ?

[robertwright]

mine was in the same location, but not as wide. look at the top left. hard to see in this example. but its there. apart from the jpeg compression...

 

squint!

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[atufte]

mine was in the same location, but not as wide. look at the top left. hard to see in this example. but its there. apart from the jpeg compression...

 

squint!

 

Thanks Robert

 

There is a lot of people getting similar "streaking" but the other

way around, with light, not dark areas, see link...

 

http://www.rangefinderforum.com/forums/showthread.php?t=69886

 

http://www.rangefinderforum.com/forums/showthread.php?t=69886&page=2

[Dan States]

Roberts shot shows shutter "tapering". Your shutter needs a tension adjustment and lube. Dag did mine 10 years ago on an M6 and 4 years ago on a III. It's an easy fix but I don't think it's for shade tree mechanics.

[atufte]

Roberts shot shows shutter "tapering". Your shutter needs a tension adjustment and lube. Dag did mine 10 years ago on an M6 and 4 years ago on a III. It's an easy fix but I don't think it's for shade tree mechanics.

 

Could this be a possible fix?:

 

YouTube - How to adjust shutters Leica M3 - DIY

[robertwright]

Roberts shot shows shutter "tapering". Your shutter needs a tension adjustment and lube. Dag did mine 10 years ago on an M6 and 4 years ago on a III. It's an easy fix but I don't think it's for shade tree mechanics.

 

you mean the left side is darker than the right-yes

 

DAG fixed that too. But the streak is something else.

[robertwright]

Here is a better example. DAG also said he polished the pressure plate.

 

Funny thing is, since it came back, the same roll of film is in it that I loaded:(

 

digital has softened my brain.

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