Jump to content

Service report help needed please


Recommended Posts

Advertisement (gone after registration)

Hi,

What does this mean in easy to understand layman's terms?

Thank you.

To correct severe tapering of exposure at 1/1000th, 2nd curtain tension had to be increased slightly to balance exposure, however this has the effect of slightly imbalancing the exposure at 1/500th and below. Without major replacement of worn parts - shutter curtain drum and spring rollers, this is the best compromise we can reach with this camera and any slight gradation of exposure is easily rectified using a linear gradient filter in Lightroom etc or dodging in the darkroom.

Link to post
Share on other sites

Simply at 1/1000 shutter speed and 1/500 they aren't accurate, or I should say within spec. They suggested a way of compensating. I've found on older Leica gear (especially the SLRs) that 1/1000 and on those camera bodies having 1/2000 speeds that actual shutter speed was well below stated speeds and once measured I knew how to compensate.

  • Like 1
Link to post
Share on other sites

It sounds like you have asked the tech to make the 1/1000th speed accurate but because the parts are worn doing this compromises the slower speeds. The result as they describe it is a gradation in exposure which means some part of the negative will be slightly lighter or darker than the rest. If you are printing your images in the darkroom to compensate for this they suggest dodging or burning the affected area (everybody knows how to do that), or in Lightroom to do similar by dodging or burning or apply a gradient filter to even out the exposure problem. 

If it was me I'd rather have all the speeds from 1/500th and longer accurate and forget about 1/1000th and any compromise adjusting it introduces. Or find another technician.

  • Like 2
Link to post
Share on other sites

10 hours ago, stvn66 said:

To correct severe tapering of exposure at 1/1000th, 2nd curtain tension had to be increased slightly to balance exposure, however this has the effect of slightly imbalancing the exposure at 1/500th and below. Without major replacement of worn parts - shutter curtain drum and spring rollers, this is the best compromise we can reach with this camera and any slight gradation of exposure is easily rectified using a linear gradient filter in Lightroom etc or dodging in the darkroom.

Could you tell us which model this is, and who did the work? I wonder whether another technician could comment on whether this explanation for the camera not running to specification after service sounds reasonable - perhaps @jerzy could comment?

Link to post
Share on other sites

1 hour ago, Anbaric said:

Could you tell us which model this is, and who did the work? I wonder whether another technician could comment on whether this explanation for the camera not running to specification after service sounds reasonable - perhaps @jerzy could comment?

It is a red dial iiif, sorry I would rather not say who the repairer is. Thank you.

Link to post
Share on other sites

Advertisement (gone after registration)

I do not want to comment advices regarding Lightroom/darkroom, I am not an expert in this.
At 1/1000 slit width is approx 1,5mm, and it shall increase slightly towards end of travel (curtains moves faster then than at the beginning - innertion). Springs in the shutter roller determine the travel speed. And if springs are damaged than they cannot fit to specs anymore - slit width may be erratic. Two left photo show an example of such damaged spring - first curtain, was overspanned extensively, most probably shutter was dirty and instead of CLA someone spanned the spring far too much. As a comparison - the second spring (closing curtain) is OK.  To some degree the reduced spring force may be compensated by the 2 excentric screws, but it is difficult adjustment and requries special test equipment, otherwise left side of frame will be exposed differently than the right side.
At slower speeds impact is not so high - slit is wider.

Does it help?

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

  • Like 2
  • Thanks 3
Link to post
Share on other sites

1 hour ago, jerzy said:

To some degree the reduced spring force may be compensated by the 2 excentric screws, but it is difficult adjustment and requries special test equipment, otherwise left side of frame will be exposed differently than the right side.

Does the repairer's note that adjusting the 2nd curtain tension had the effect of 'slightly imbalancing the exposure at 1/500th and below' giving a 'slight gradation of exposure' suggests that this difficult adjustment was either not performed (perhaps they didn't have the test equipment), or was not possible with the current state of the 'drum and spring rollers'? Can these components be replaced if necessary, or are spares unavailable?

Does their general approach of dealing with tapering at 1/1000 by increasing the 2nd curtain tension sound reasonable, or is there some better remedy for this? I've seen previous suggestions that some repairers resort to tension adjustments as a quick fix, when they should really be doing proper cleaning and lubrication first. But perhaps that doesn't apply if the shutter components are too worn, as the repairer claims?

  • Like 1
Link to post
Share on other sites

Left photo originates from Leitz publications and shows how the shutter was tested using light drum. Light drum (Lichttrommel) was shown and explained few times here in LF.

Right photo is from IIIf service manual. Is a bit weird but it explains the impact of spring span and the 2 adjustment screw that I mentioned earlier.
White stripe is the slit which travels from right to left. Curve 1 represents the first, opening curtain, curve 2 closing curtain. Blue arrows are pointing to slit width at the beginning and end of travel.
We can notice 2 things: - slit is wider at the end and both curves are more flat towards end of travel. Flatter curves tell us that curtains travel faster at the end. When slit travels faster the exposure time is shorter and in order to compensate the slit is wider to achieve the same exposure time at the beginning and the end of the frame. All this is realised by the characteristic of both shutter springs. As I shown above they are different for 1st and 2nd curt and this is because besides moving the curtains other components are involved (gears for film transport, curtain brake, gear for slow speed delay, etc)
When spring  for opening curtain is spanned more the curve became flatter, slit is wider at the end, exposure is shorter at the end. When the spring for closing curtain is spanned more slit will be narrower at the end, frame will be under exposed there (shutter capping).
So the tension of both spring needs to be adjusted to achieve curves similar to above, to achieve that slit gets a bit wider at the end.
Now the the 2 eccentric screws mentioned earlier. They determine when the closing curtain will be released, thus they have impact on slit width at the beginning. Proper order when adjusting shutter is:
1. Span both springs to get travel time of approx. 18ms (for IIIf black dial)  and curves similar to the picture
2. Adjust screws to get correct exposure time
I want to discourage you to change setting of both eccentric screws unless you have light drum and understand what you are doing, it is not so easy.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

  • Like 1
  • Thanks 3
Link to post
Share on other sites

vor 3 Stunden schrieb jerzy:

When spring  for opening curtain is spanned more the curve became flatter, slit is wider at the end, exposure is shorter at the end.

Corerection: this is wrong, shall be: "....slit is wider, exposure is longer at the end"

Link to post
Share on other sites

A CRT tv can also be used to view the shutter curve jerzy shows, although you need to try several times to catch the full curve. I’ve used this for years for checking shutter adjustments. Too bad digital tvs won’t work this way, but I keep a CRT tv with vcr as a signal source to check old cameras I acquire.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...