[LargeFormat] Winter oil change

[Richard Knoppow]

----- Original Message ----- 
From: "philip lambert" <philip.lambert@ntlworld.com>
To: <largeformat@f32.net>
Sent: Sunday, January 18, 2004 4:57 AM
Subject: Re: [LargeFormat] Winter oil change


> Cautionary tale:
>
> I am replacing my 180mm TeleArton f5.6 with a 180mm Symmar
as I no longer
> need the short back focus and welcome the wider field of
the Symmar.
> However this came in a Synchro-Compur shutter that is
slow, sometimes by
> half a stop or more  and some speeds aren't the same twice
in succession. I
> put the  shutter for three hours in a petrol-vapour
atmosphere  (having
> taken the glass out). Hitherto this has softened up
coagulated lubricant to
> good effect but on this occasion had adverse results.
> The speeds 1sec 1/2sec, 1/5 sec stopped working or were
unpredictable.
> Higher speeds worked but 1/100 was timed at 1/90 to 1/120,
1/200 was nearer
> to 1/125 and 1/400 was approx 1/200 or worse.
>
> These odd effects were temporary, as a day later as the
slow speeds were
> working again and most speeds were more or less a half
stop slow. I can live
> with this if speeds are consistent by putting a small
correction table or
> note  on the lensboard. Over-exposure doesn't bother me on
negative film
> (although it would on 'chromes) but unpredictable speeds
are a bother.  I
> suppose a professional overhaul would be good. Regrettably
the firm I used
> for my 203mm Ektar didn't do much of a job.  Philip
>
>
   The shutter needs a real cleaning. I think the reason it
behaved so oddly after the vapor treatment is that the
solvent hadn't completely evaporated and was causing the
shutter blades to stick together. The Syncho-Compur is a
good shutter, as good as any made now, but it needs a
thorough cleaning and lubrication with the proper
lubricants. Once cleaned the speeds will be consistent.
   Note that the top speeds are calibrated in terms of
_effective_ exposure time for the full aperture of the
shutter. Measured for total open time (open time at the
center) they will be about 20% slow. The spec for the #1
Synchro-Compur is about 1/380th at the marked speed of
1/500th.  All blade shutters are calibrated this way. The
slow speeds should be quite accurate up to perhaps 1/100th.
   Try Steve Grimes shop for the shutter work,
http://www.skgrimes.com

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com