Hi, I have recently got into large format photography and have a Chamonix 45N-1. I went through a whole bunch of grief with the groundglass/fresnel lens issue associated with this camera, as I was shooting with a Xenotar 150mm 2.8 and was consistently getting stationery subjects coming back out of focus. I thought i was going mad to be honest until I slowly but surely saw other people appearing on this forum with similar issues.
This issue has since been resolved by having a Maxwell screen installed and my back being measured by Bill Moretz at ProCamera. So far so good with the results..
In my quest for information with regards to shooting wide open with this lens, he said that as depth of field was so minimal at that aperture, that I would also need a darkslide that was in very close relation to the groundglass back..
Since then, I have read a few articles that state what the ANSI standards are for darkslides ( 0.197 +or- 0.007 ) and that ultimately film holders depth should be aiming for 0.190. For example, apparently Sinar manufactures its backs to 0.190.
This is one article that I am referring to
http://www.largeformatphotography.in...-holders.3.gif
So my first question is, if the standard is + or - 0.007 why is the depth we are aiming for 0.197. Isn't that only taking into account the minus. Wouldn't it be a range from 0.190 to 0.204?
Most articles seem to aim for this number of 0.190, could someone please explain this to me?
Also, recently I had a friend test some of my darkslides at a printing factory where he works and I was surprised at what some of them came back as. Most were pretty good but one came back as 0.224! Just on one side as well..
So, I was hoping that someone could suggest an online store or something where I could buy a depth micrometer that wasn't super expensive and was capable enough of testing my double dark slides.
I live in Melbourne, Australia and have enquired at a few stores without much success ( not that were reasonably priced anyway ).
I did see this one on Ebay but am not even sure if this is what I am after...
http://cgi.ebay.com/200-mm-Digital-C...#ht_2119wt_941
It also states that it is accurate to 0.02mm or 0.001in, is this enough?
Any information that any one could provide would be greatly appreciated! Best Regards Josh
Oh yeah, and if anyone could please pass on a good test with such an instrument that would be awesome.. Thanks again.
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