[pure-silver] Re: [OT] Filmholders, Septums, Total-Disasters

  • From: DarkroomMagic <info@xxxxxxxxxxxxxxxx>
  • To: PureSilverNew <pure-silver@xxxxxxxxxxxxx>
  • Date: Tue, 03 Jan 2006 22:11:48 +0100

I check holders without film (easier and more robust to measure) for
deviation to the standard but subtract the average film thickness (0.007 in)
to verify that ground glass and film are in the same plane.





Regards



Ralph W. Lambrecht

http://www.darkroomagic.com







On 2006-01-03 21:06, "richard l. gifford" <rlgif@xxxxxxx> wrote:

> Richard Knoppow wrote:
> 
> (snipped)
>>  
>>   ...While the ANSI spec for the holders is written for no film film should
>> be put in them for measurement. ...
>> 
>> ...ANSI Standards for film plane placement in sheet film cameras.
>> Size    Location   Tolerance + or -
>> 
>> 4x5     0.197    0.007
>> 
>> 5x7     0.228    0.010
>> 
>> 8x10    0.260    0.016
>> 
>> Dimensions in inches.
>> Film thickness is 0.007 inch  The above does not include
>> film thickness.
>> 
>> ...Remember that the film plane distance in a _camera_ is the above minus
>> the 0.007" film thickness.
>> 
> 
> 
> Reading this prior to filing.  Wondering if you are
> mixing apples and oranges.  You say the ANSI spec for
> holders is written for no film, which makes sense
> because the spec is for the holder.  Then you give ANSI
> locations for film plane placement, which would
> logically be different from the holder dimension.  This
> strikes me as a strange ANSI standard since it's a
> function of film thickness.  And a strange duplication
> of effort if they already have a better standard for
> just the holder.  So I proceed with caution.  You said
> to measure with film, which would only make sense in
> order to compare with film plane placement standards
> and not with holder standards, so this supports the
> idea of two standards.  You say the above does not
> include film thickness, and this statement is more
> troublesome than clarifying to me, considering that we
> are measuring with film.  I could interpret this as
> meaning it is the dimension to the film and therefore
> does not include film thickness.  Or I could interpret
> this as meaning it is the dimension to the holder and
> therefore the film thickness is not included.  But then
> you say the film plane distance in a camera is the
> location stated above minus the .007 film thickness,
> which would only be so if the stated location were for
> a holder standard and not for a film plane placement
> standard.
> 
> Granted, the difference of .007 isn't much.  But given
> that it's equal to the allowable deviation in 4x5, it
> seems worth wondering about.  Do the dimension
> standards given apply to the holder or to the film
> plane location?  I can't find my earlier file used to
> check my holders, or I would venture an opinion.
> 
> Regards...  Dick Gifford
> 
> 
> 
> 
> ==============================================================================
> ===============================
> To unsubscribe from this list, go to www.freelists.org and logon to your
> account (the same e-mail address and password you set-up when you subscribed,)
> and unsubscribe from there.


=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your 
account (the same e-mail address and password you set-up when you subscribed,) 
and unsubscribe from there.

Other related posts:

  1. Home
  2. pure-silver
  3. Archive
  4. 01-2006