Is your backfocus Excel spreadsheet correct?

Discussion in 'Off Topic' started by Martin Pugh, Mar 6, 2022.

  1. Martin Pugh

    Martin Pugh Cyanogen Customer

    Joined:
    Oct 27, 2014
    Messages:
    371
    Hi Doug

    I have asked a few other folk about your backfocus spreadsheet, in particular in regard to the modification of the available backfocus when selecting a filter.

    We seem to be in agreement that when you add a 3mm filter to your system, it extends your backfocus by 1mm, but if I select a 3mm filter in your spreadsheet it subtracts 1mm.

    I dont think this is correct, can you clarify?

    Martin
     
  2. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
    Messages:
    9,932
    D'oh.

    It's fixed. Also added 5 mm filters.

    Thanks
     
  3. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
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    @Martin Pugh I had it right the first time.

    The spreadsheet calculates the total back focus required by the camera. That subtracts from the back focus of the instrument.

    The filter increases the available backfocus, so it should be negative in the spreadsheet. Double negative!
     
  4. Martin Pugh

    Martin Pugh Cyanogen Customer

    Joined:
    Oct 27, 2014
    Messages:
    371
    Doug...Yep, I follow.
     

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