The IRD-3 Two-Bath Developer 
3 grams. (para-methylaminophenol) FIRST BATH 
(a) Metol 
Sodium Sulphite (anhydrous) 35 grams. (Na, SO, ) 
Water 1 litre. 
pH = 8.0 
(b) Metol 5 grams. 
Hydroquinone 4 grams. (CH, (OH), ) SECOND BATH 
Sodium Sulphite (anhydrous) 40 grams. (Na, SO, ) 
Sodium Carbonate (anhydrous) 15 grams. (Na, CO, ) 
Potassium Bromide 1.5 grams. (KBr) 
Water to 1 litre. 
pH = 10.1 
First trial with IRD-3 and FE 120 Unit 
Aviphot Pan 33 Aerial Film, 76 meters, 24 centimeter wide, with sensitometric step tablets and resolution 
targets low contrast (modulation = 0.21) and high contrast (modulation = 0.95). 
1. Pre-soak dry-to-wet: one pass in water 20°C 
2. First bath: Four passes 20°C 
3. Second bath: Eight passes 20°C 
Sensitometric analysis: (23 meters from end of film) - figure 1 refers - (dotted line) 
Effective Aerial Film Speed (EAFS): 92 
Fog: 0.32 
G (average gamma): 1.5 (range 1.0 log-units from speed point on) 
Maximum density: 3.15 
EG&G Mk VI Sensitometer: 
T = l0 seconds, H - exposure - 10? Juxseconds ; Ho - 0.01621xs. Neutral density for step tablet = 2.25; 
Neutral density for resolution targets = 2.98 . 
Resolution target analysis: 
  
Low contrast target (Modulation 0.21) - D ax 21.71, D ta = 1.52. Resolution = 36 line pairs per mm. 
High contrast target (Modulation 0.95)--D __ = 1.88, Doin = 0.27. Resolution = 57 line pairs per mm. 
From the data it is obvious that the fog level is high (0.32) for comparitively low effective film speed 
(EAFS = 92), but this is quite within the authors' experience for this fiom with developers such as DK50. 
The maximum density at 3.15 is rather too high of course, as is the gamma, but these parameters were seen 
to be smply due to excessive processing, it was the shape of the curve that really was of interest! 
The formulation of IRD-3 was based on trying to gain curves such as shown in figure l, steep gradient in 
the toe with an S-shaped decay at the shoulder. The toe gradient is needed in order to gain maximum speed, 
ss shown by Eq:l EAFS - 1.5/H, (Eq:1) where H is the exposure energy required to gain a density level 
of 0.3 above base plus fog- 
There was no sign of bar-marks but in the absense of topographic imagery this test could not be relied 
on to make claims in this respect. The targets showed good resolution and they were recorded well down 
the entire length of the film, they also showed considerable Bromide streaming over the high fog level 
of the film. 
Second trial with IRD-3 and FE 120 Unit 
The second trial was carried out at the ITC Enschede (Lorenz/Wilbrink) and consisted of a full length of 
76 meter being flown from the ITC aircraft, sensitometric data being exposed onto the film (EG&G Mk VI 
no. 832), and Zeiss FE 120 Rewind Spool Tank processing unit in IRD-3 two-bath developer. 
In this experiment the films were Kodak Double X 2405 and Agfa-Gevaert Aviphot Pan 200. The Double X 
was rated was rated at the’ EAFS = 250 (from previous experience as though developed in DK50 for 8 passes 
in RWST). Splitting the film into two length the first development was undertaken with (a) 4 passes - 
14 minutes, and (b) 8 passes - 28 minutes. The base plus fog density was 0.34, the EAFS = 320 and 
G =1.6 (over a logH-range of 1.0). There were no bar marks but streamers were very obvious. In the 
second process of the Double X the development was reduced to: (a) 2 passes at 20°C and (b) 4 passes 
at 20°C, total processing time 42 minutes. G was-averaged at l.l, fog level at 0.23, maximum density 
was 1.4 (buildings in Enschede), minimum density was 0.4 (wooded areas), and the most-important of all - 
no bar marks were observed and no streamers from the barges observed in the canal harbour at Enschede! 
As the barges gave a density of 1.6 against the canal density of 0.6 the lack of streamers in this trial 
was most encouraging. The mission was flown with a Zeiss RMK A 15/23 aerial camera at a scale of 1:6 000, 
and with a shutter speed of 1/500 seconds the calculated image motion was 20um for a ground speed of 
120 knots. A resolution target of 40:1 modulation was placed on the roof of the ITC building and resolved 
28 line pairs per millimeter. 
The second film - Aviphot Pan 200, exposed for EAFS - 250 (based on previous experience) was cut in two 
parts as well and developed in two processes: The first process in IRD-3 with 4 passes - 5 minutes (a) at 
20*C and 8 passes - 10 minutes (b) at 20*C; the motor drive has been used. For the second process half 
the number of passes each was applied with a total time of 7 minutes (result of sensitometry see figure 2); 
fog level 0.14 and 0.12, G - 1.6 and 0.9 to 1.0; the fog level is remarkably lower and no streamers do 
appear! This testing will be continued, also including Ilford FP3 and HP5. 
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