Page 15 - RD_2000-12

if l5mm sound tracks could be directly contact strain on the film now traveling at the higher
printed, Iiiii si:tc, on to l6mm picture prints, and speed of 18" per second. (Remember that in the
then nm, during pn~jcction at the correct linear 1930s much tri-acetate film was liable to
speed l(>r _l_'lmm sound tracks of 18" per second. become brittle and crack and much
This is more than twice the speed of 16mm development was being carried out by the
S.O.F. of 7.2" per second and left the problem manufacturers to improve its flexibility and
of how to marry the 16mm picture speed of 72" long term characteristics).
per secoml with the 35mm sound track speed of Harper designed a new film perforator Ref.4 to
18" per second on the one strip of 16min film. produce this new type of 16mm film stock but
this is not mentioned in the Patent
Harper's solution to this problem was to design Specification.
a special dual-purpose film printer for which he
obtained a British Patent Specification No. In order to obtain his special 16mm projection
509009 lin· which he applied on January 4th prints Harper designed a special and rather
1938. TilL~ complete specification was left on complicated dual-purpose printer. This is
May 14th 191X and accepted on July 4th 1939. described in great detail in the full Patent
Ref:J. Specification and is too lengthy and involved to
reproduce here. On
To achieve his aim the the first run through
area available on the printer the optical
16mm had to be sound track of the
reallocated. l·:dge 3 5mm film was held
perl(mttions were no in intimate contact
longer used. lrnm each with one of the 3mm
side of the lilm were wide tracks on the
reserved l(>r sound l6mm print stock. A
tracks leaving IOmm in second print run was
the centre llx the width then undertaken
U\ N
of the 16mm picture 0 whereby the pictures
frame. The height of a c ! corresponding to the
:1
0.
35mm picture frame is , optical track were
-t
18. 75mm <uH.I this wa-; '1 optically reduced on
D
divided as l(>llows: - 2- I. to the print stock but
2.75mm was utlised 1- each successive
"0
used by two l c picture frame was
!
:1
perf(mttions of 35mm ... ~ printed on to every
standard size set either other frame on the
side just inside the 16mm film. The
3mm margin reserved process was then
for the sound tracks. repeated for a second
Then two 8mm spaces reel of 35mm film
for the 16mm frame whereby the other
heights plus the 3mm track on the
2.75mm perforations 16mm film received
equal the 18.75mm of Fig. 1 Fig. 2 the second 35mm
a 35mm frame. This track and then the
resulted in the format pictures of the second
shown in fig I. At later stage of development 3 5mm reel were printed into the frames spaces
this l(>rmat wa<> modified slightly to left blank by the first run.
accommodate a third centrally placed sprocket This resulted in a 16mm film which carried two
hole. Fig 2. This was apparently to ease the reels of 35mm film and sound with the pictures