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Homemade Pentax 67 vacuum back - advise please

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#26 Nightfly

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Posted 10 October 2014 - 05:23 AM

Glad to hear it is working out Michal.  It will be good to see your results.

 

 

A member at Pentax Forums ran into a home-made vacuum back recently.  I post here in case anyone was interested.

 

http://www.pentaxfor...-man-parts.html



#27 Michal1

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Posted 21 November 2014 - 05:03 PM

My next film has been developed. I intended to use the vacuum back, but the battery in it got dry during the second shot. The power supply has been not solved very well yet, so I wasn't able to replace the battery. I'm writing this to share a finding. If you have problems with the curl of 120 film, then consider removing the backing paper as desribed here:

http://www.sciencece...0film/index.htm

I was afraid that the using of my vacuum back without vacuum would result into severe curl of the film. However, the opposite came out to be true. No frame on the film shows a trace of it. Many of them had the exposure time of 50min. I consumed the whole film during a single night, which was very humid. There was light haze near the ground for the whole night. The paper probably absorbs the humidity from the air and becomes wavy.



#28 Dave Kodama

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Posted 21 November 2014 - 10:12 PM

Michal,

 

Interesting theory regarding the paper backing.  That could indeed make the difference between success and failure.  However, in my thankfully limited experience (when forgetting to turn on my vacuum pump after advancing my film) it seems that negative film is more prone to curling.  Perhaps the different thickness of the base or coating differences explain that.  Also a fast lens is more likely to show problems when vacuum is not used.

 

Dave








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