[PADG:1608] Microfilming Connecticut aerial photographs

["Jane Cullinane" <JCullinane@xxxxxxxxx>]

I've been trying to understand what the optimum requirements should be
for a project to preserve and improve access to 10,484 black and white
aerial photographs (approx. 7 x 9 inches) made in 1934. Right now I'm
giving primary consideration to 35 mm continuous tone microfilm (chiefly
for financial reasons.)

I'm familiar with the specifications for using with high contrast black
& white film for filming newspapers but have not been completely
successful in figuring out what my requirements should be when working
with continuous tone film, especially with regard to the density of
photographic images.

While I have confidence in the work of the vendors I know about (NEDCC
and Preservation Resources), I do have to get three bids and go with the
qualified vendor with the low bid. Right now, I lack confidence that my
specifications will eliminate the unqualified vendors. 

Based on my newspaper microfilming experience and recent research, I
have several statements about my specifications that I hope you will
comment on. Is there anything in these statements that will contradict
what you know about filming with continuous tone microfilm? Can you
suggest a project or report that will discuss the specifications for
this kind of work?

1 -- The vendor shall produce the following 35 mm continuous tone,
polyester based, safety microfilm for each newspaper:
--One silver negative, first generation preservation master microfilm,
which shall be used only to produce:
--One second generation silver negative intermediate printing master,
and from that:
--One positive silver-halide service copy.

2 -- For the master negative (first-generation), the resolving power of
the camera system should be 120 lines per millimeter or higher.
Succeeding generations should exhibit a loss of not more than one
resolving power pattern per generation. The resolution will be
determined by finding the lowest pattern resolved on any of the 5 test
charts in the frame at the beginning and at the end of the reel.

3 -- Background density on the master negative shall be no lower than
.80 and no higher than 1.20. Base-plus-fog density (Dmin) shall not
exceed .10. Each reel shall be inspected with a transmission
densitometer. No less than five readings shall be taken per roll, at the
beginning, middle and end of the roll. During filming, the camera
operator shall make an effort to make the density of the negative images
relatively even throughout the roll.

Thank you, in advance, for you continuing help,
--Jane C.



Jane F. Cullinane
Preservation Librarian, Collection Management Unit
Connecticut State Library
231 Capitol Ave., Hartford,  CT  06106-1537
860-757-6524, fax: 860-757-6559
jcullinane@xxxxxxxxx     http://www.cslib.org