Schneider lens

[chris_autio]

My lens quit exposing properly for 1/4, 1/2, and 1 sec. But all other shutter times seem ok. Is it a timing spring that needs work?

[kmac]

What exactly happens, are those speeds just too slow? The shutter may need a good internal clean to remove dirt and grime.

[Niels - NHSN]

Large Format shutters are mostly not very reliable with age and it is common pratice to maintain a personal shutter equivalent list specific for a given shutter. For example: 1/500=1/300, 1/250= 1/180 etc.

The slower speeds are often not used (in my experience).

My exposures are usually counted in seconds (B) or around 1/60-1/250. Other speeds are rarely used and may dry up over time unless exercised but may still drift.

As long as things works reasonably predictable I would be reluctant to pay for repairs.

[Niels - NHSN]

BTW - the title ‘Schneider lens’ is misleading - your problem is related to the shutter which is made by a different producer.

[AlanKlein]

Manufacturers guarantee shutters less than 1/3 a stop off when they were new.  So, I checked my lenses during the last year or two and all were under 1/3 off at all settings.  Most settings were right on. Most were much better than that, beyond my expectations.   Lenses checked: 75mm Fujinon f/5.6; 90mm Nikkor SW f/4.5, 150mm Schneider APO Symmar f/5.6; 300mm Nikkor M f/9.

Edited October 21, 2022 by AlanKlein

[chris_autio]

I know most shutter speeds are not exact because I had them tested, but the aforementioned 1/4,1/2 and 1 sec are now about 1/60. 1/8 sounds like 1/8

[Niels - NHSN]

4 minutes ago, chris_autio said:

I know most shutter speeds are not exact because I had them tested, but the aforementioned 1/4,1/2 and 1 sec are now about 1/60. 1/8 sounds like 1/8

So what do you hope to get from this thread?

If you can't live with the discrepancy the answer is simply and obviously: get it repaired.  

I would ask myself if I even use the shutter speeds in question before deciding.

[rodeo_joe1]

Regardless of the make, most LF leaf shutters follow a fairly standard engineering pattern. The slow speeds are governed by a separate timing module that can be heard winding up and running down when the shutter is respectively cocked and fired. 

So a quick diagnostic of listening to the shutter as it's cocked and fired at slow speeds might go some way to determining the fault. 

Is there any 'whirring' sound at all? 

The Slow Speed (SS) module is held away from the the main shutter cog by regulating cams, and only engages with the main cog at slower speeds. The distance it engages regulates the amount of time it holds off the shutter from closing. 

A complete loss of slow speeds could be caused by any of the following:

The spring tensioning the SS module toward the main cog might have snapped or detached. 

The pivot adjustment that regulates the slow speeds might have loosened and allowed the SS module to disengage completely from the main cog. 

The SS module itself might have jammed, but this is more likely to prevent the shutter from closing at slow speeds.

The only way to fix the issue is to strip the cover off the shutter and have a look-see at what's happening. Because no amount of spraying lubricant or solvent (Aaaaargh! 😱) is likely to improve things. 

 

 

[Chris Autio]

After a few mornings out in the field, this particular lens’ shutter speeds all failed. I will have to send it in to get repaired. Meanwhile I have been shooting with 75mm. Processing HP5