would have the dis- 
vback especially for 
: phosphor) by using 
Iter would be effec- 
even among military 
ts for such as speed 
ing power. Without 
write. In this case 
reed standard which 
ntended that sensito- 
ifferent laboratories 
s difficult to obtain, 
o industrial and two 
neasurements do not 
s quite sufficient for 
much research effort 
nterpretation of the 
tests closely related 
. autumn 1959. Some 
" the present version 
. I would especially 
Stockholm. 
ny useful discussions 
sion, Royal Aircraft 
;) were measured by 
Ministry of Aviation 
s of Fig. 6. 
' (1) (Figs. 9 & 16); 
); and Blaschke (4) 
ipplied by Mr. Raife 
, for Fig. 1 and the 
, 
+ CT testing, and the 
self be a formidable 
rences in some of the 
THE PHOTOGRAPHIC IMAGE, AUTHOR'S PRESENTATION 
papers listed below, particularly in (4). This list is not intended to be a representative 
survey of the subject by itself. 
[1] Washer, F. E. The Testing of Photographic Lenses at the National Bureau of 
Standards. Photographie Engineering, 1954, Vol. 5. No. 1. 
[2] Lindberg, P., Measurement of Contrast Transmission Characteristics in Optical 
Image Formation. Optica Acta, 1954. No. 2. 
[3] Sproson, W., New Equipment and Methods for the Evaluation of the Performance 
of Lenses for Television. B.B.C. Engineering Division Monograph, Dec. 1957. 
[4] Blaschke, W., Scientific Approach to Assessing Image Quality. Journal of Photo- 
graphic Science, Nov./Dec. 1959, p. 163. 
This issue, published after the first draft of the present paper had been circulated, 
contains a valuable review covering much of the same ground in more detail in a series 
of papers by Selwyn, Linfoot, Powell & Blaschke. 
SUMMARY. 
The paper is concerned with the quality of the images which form the basis of aerial 
photogrammetry and is largely devoted to a discussion of the potential advantages of 
frequency response testing over current resolution tests. Frequency response testing gives 
much more information about lens and film performance, and frequency response curves 
can probably be used to predict the cascaded performance of all the elements in an 
aerial photographie system. A diversity of test methods has been proposed; all of them 
involve greater skill and more complex equipment than photographie resolution testing, 
which is likely to persist as a simple and informative method for assessing camera per- 
formance, though it will gradually be displaced wherever a complete analysis is required. 
Frequency response testing, and the presentation of its results, must be speeded up by 
automation, but the greater complexity of equipment required will tend to restrict its 
use to the larger laboratories. 
The difficulty of carrying out tests of airborne camera performance is briefly dis- 
cussed. 
Reference is made to progress in negative emuisions which leads to improved image 
31 
quality. 
Author's Presentation of the Paper 
First of all, I must apologise for some 
printing errors in the invited paper published 
in *Photogrammetria". Unfortunately, I never 
saw any proofs and it was not possible to check 
before the thing went into type; but I trust the 
errors will be obvious to people able to un- 
derstand what was intended. 
I do not want to spent a lot of time repeating 
what I have already said in the paper, and pos- 
sibly I have said too much. All I want to do to 
save time is to bring before you one or two 
thoughts which seem to be more important in 
this question of frequency response or CT 
testing. I do want to emphasise that I am not 
speaking — and I think most people will not be 
speaking — from a large background of fre- 
quency response or contrast transmission mea- 
surements. This is a thing which is easy to write 
about but in my view it is not too easy to 
measure. A great deal has been said, but to the 
best of my knowledge there is no large back- 
ground of measurements on lenses of the kind 
we use in photogrammetry. So all the time we 
are speaking in a slightly unreal atmosphere; 
in the old resolution test we have a large back- 
ground of experience and we know what we are 
talking about. 
I will try and give my general impressions, 
again in a very short form. First of all, it seems 
obvious to me, personally, that this contrast 
transmission method of testing lenses in the 
method of the future, and it is obviously the 
thing for which we should all work. There are 
several reasons for saying that; at the same time, 
I do think we should hear a lot of opinions on 
this and perhaps even go to some sort of vote 
as to whether we generally agree this is an im- 
portant thing for photogrammetry. 
The first thing I would put forward is that 
the frequency response or contrast transmission 
function for a lens is at last some definite phy- 
sical property of the lens which, in principle at 
any rate, is much easier to define than anything 
like a resolution test, which is a complex 
function of several variables and is not nearly 
so repeatable. I say to define in principle and