Conclusions 
Conc uso 
The IRD-3 two-bath process seems to exhibit encouraging results from the Kodak Double X and the Agfa- 
Gevaert Aviphot Pan 200 trials held at ITC. Relative freedom from the well known artifacts was the 
first goal of these trials and it seems that the process may have overcome these problems, providing 
that the maximum density of the imagery is kept below l.4, and gamma below 1.2, as shown in the experiments 
with Double X; with Aviphot Pan 200 the gamma might even go up to 1.6 as no remarkable streamers do 
appear at this gradient. The sensitometry of Double X - see figure 1 - and of Aviphot Pan 200 - see 
figure 2 - establishes good working film speeds with EAFS = 250 for Double X and EAFS = 200 respectively 
160 for Aviphot Pan 200. Future trials must be carried forward with other materials as Ilford FP3 
and HP5 and IRD-3 process as well as with Kodak Plus X and Aviphot Pan 150. The latter tested at smaller 
scales and with increased process in the second bath. No doubt there will be problems with streamers when 
processing is increased, but some variations in the KBr content may be the answer since it is known 
that by increasing Bromide content streamers tend to be inhibited, fog reduced, and contrast increased - 
all at the expense of film speed however (6). 
It may be of interest to relate that the role of the first development (a) bath seems to have been 
justified since sensitometric data show the (a) curve to have a gamma of only 0.12, a maximum density 
of 0.2 (on average), and serves only to prepare the film for the second (b) bath which, as designed, 
does all the work and will hopefully prove to be tolerant of adjustment to other materials. 
Figure 3 - 
gives some information about the spread of the RWST process - centre side and edge side of 
a processed step tablet along the edge of films and the mentioned difference between centre and end of 
films, the typical RWST processing effect. Those remain subject to be tested and investigated intensively. 
REFERENCES 
(1) Walker, L. 1967. Evalutation of Aerial Film processing. Dept. Energy, Mines & Resources, Ottawa. 
Project report 67/29. 1967. 
(2) Worton, F J. 1976. Aerial Film processing by the Rewind method. Photogrammetric Record 8(47): 
652-660. 1976. 
(3) Thomson, G H. 1973. Aspects of Aerial Film processing for Photo - Interpretation in Resources 
Surveying. ITC Journal 1973-3. 
(4) Smith, W P. & Worton, F J. 1964. The Aerial Photograph. Report of proceedings of the Conference 
of Commonwealth Survey Officers. HMSO, London. Vol.l. 1964. 
(5) Graham, R W. & Lorenz, R W. Internal memo. ITC Enschede. August 1976. 
(6) Mason, L F A. 1966. Photographic Processing Chemistry. Focal Press. London. 1966. 
Figure 3 
Spread of sensitometric data 
caused by rewind spool tank 
processing (step tablets exposed 
along edges only). 
(0) Reference film Aviphot Pan 33; 
first trial processing. 
(1) Double X 2405 - 
averaged curve (——————) 
and spread (-------- ) 
indicating areas at the end (D) 
and at the centre (A) of the film 
respectively at the centre 
side (B) and at the edge side (C) 
of step tablets along the edge 
at the middle area and areas near 
the ends of the film. 
(2) Aviphot Pan 200: 
from above - 
a. middle of film (A) 
b. centre side along edge (B) 
c. edge side along edge (C) 
d. ends of film (D) 
The data for the curves are 
actually measured. 
(1) and (2) were processed in 
IRD-3 with 
4 passes and B passes. 
(3) Double X 2405 
(4) Aviphot Pan 200 - 
Processed in IRD-3 with 
2 passes and 4 passes. 
  
END 
  
  
  
  
  
  
  
  
A 
v 
DEVELOPER 15 
SQUEEZED OUT 
  
minm E) 
CENTRE MIDD END 
Pd 
ut, o 
mtr il 
or 
L A 
206 
  
-1.0 
log rel. exposure 
  
log H[trs] = 7 02 CR 
0.0