Luminous Landscape Forum

Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: heinrichvoelkel on April 24, 2021, 01:57:36 pm

Title: Arca Rmdi and IQ4 problem
Post by: heinrichvoelkel on April 24, 2021, 01:57:36 pm

Hello,

what am I doing wrong? I have an Arca Rmdi and a IQ4 back with 47mm and 75mm lens. The 75 runs smooth. Using the 47 I experience following problem. When exposing for 1 second or bulb, the back ends exposure before the shutter ( Copal ) closes and I end up with an underexposed picture. Any hints?

Kind regards from Germany,
Heinrich

Title: Re: Arca Rmdi and IQ4 problem
Post by: anwarp on April 24, 2021, 07:02:47 pm

I suspect poor contact within the switch in the shutter.   It most probably doesn’t remain closed for the full duration.  Perhaps the contacts are dirty or oxidised. 

It’s easy to test if you have access to a scope. 

Title: Re: Arca Rmdi and IQ4 problem
Post by: Rod.Klukas on August 06, 2021, 05:34:24 pm

Yes, the sync in the shutter needs adjustment.  The past 10 years I have observed several 47mms in particular with this issue.

Find a good place that does Copal repairs.  It probably does not require parts.  Christoph Greiner may do these repairs.

Rod

Title: Re: Arca Rmdi and IQ4 problem
Post by: Paul2660 on August 06, 2021, 06:25:46 pm

Or use the e shutter from the back. With my RM3DI and IQ4 I rarely use the copal as it’s so inaccurate in set shutter speed vs observed. For these exposures you would be on a tripod I assume so the e shutter would work. Plus you can take advantage of frame averaging and or dual exposure.

Paul

Title: Re: Arca Rmdi and IQ4 problem
Post by: vjbelle on August 09, 2021, 11:38:12 am

For sure you should use the E shutter instead of the copal unless you 'really' need the copal. 

Victor B.