8. Incorporation of Transfer Function Measurement in 
"Recommendations for Camera Calibration" 
The Resolution 1.5 envisages "an agreed method" to be 
incorporated in ISP "Recommendations for Camera Calibration" 
by the 1968 Congress. The Working Group does not feel that 
it can recommend any particular method to the exclusion of 
others, because from the fundamental nature of the transfer 
function the particular method employed is not important, 
all methods being equivalent in principle. It is of far 
greater importance to ensure that whatever method is employed 
should be thoroughly tested and qualified under the widest 
possible range of conditions before it is used, and that a 
satisfactory proof of accuracy be available. The actual 
method employed is then a matter for the choice of each 
laboratory. 
Since the "Recommendations" is not a standard and 
does not include limits or suggested performance standards, 
the question of including recommended transfer functions for 
particular applications does not arise. It is suggested that 
to introduce quantitative notions into general circulation, 
typical transfer functions of known excellent lenses, measured 
according to the best known methods, should be published, for 
example in Photogrammetria. 
The Working Group has composed a suggested section, to 
be incorporated as a supplement in "Recommendations", dealing 
with precautions, details of test techniques, numbers and 
types of measurements, and expression of results. This supp 
lement is offered tentatively, for incorporation only if 
approved after wider circulation and discussion in the meet 
ings of Commission I. The suggested supplement will be found 
in Appendix 5* 
9. Interpretation and Use of Transfer Function Measurements 
It must be assumed that in due course OTF measurement 
techniques will be developed to an acceptable level of acc 
uracy and standardization. The question then arises, as to 
how the measurements are to be interpreted and applied for 
the purposes of aerial photography. 
Application even to the limited objective of specifying 
the performance of lenses on an accepted quality scale, 
cannot be entirely divorced from interpretation. At present 
the user of a lens can obtain a performance figure (resolving 
power) which indicates the limiting size of a standard target 
that the lens will reproduce in combination with a specified 
emulsion, thus providing an intuitively acceptable bridge