fro» centre. In this case we can evaluate a vie« 5. Conditions for viewing the fils 
circle with a diameter of 166 m at a fils fortat of 
242x243 m. 
at]on. 
operty 
Modulation transfer of fils 
The viewing of air photos is generally like an opti 
cal enlargement of the origin. This can be either vi 
sual viewing or making a copy. The observation of 
distinguishable details depends on the enlargement 
scale of the used objective (of the enlarger) and its 
transfer by one modulation transfer function. Accord- modulation transfer function. According to destin 
ing with practical demands the determination of the guishable details the enlargement of air photo is a 
fi 
Ì r »CL y. P hP 'v P 
fit nave tr>e pcs* 
+ n rc,z 
escrise 
: l r it. 
•lì ¿ a11 o;> l >■ cir>sftr? f ¡j ■ : c t1 or &y analysis of 
duced edge is the best one. The modulation transfer 
functions of the aerial film VF 45 at d 
sities between edge and surround are shown a 
displacement 
frequency 
spatial trequeue/ ¡.o o .owt 
i at i on 
i a !. i on 
> ; Spi e 
, have 
idudf 8 
ie set 
© m R 
- * v> _ j. i. r __ r itr * r -i j: ? 
, y* i nCOUidiiC^ U tíííbTB? Li £ 5 tres Cfr Vf *tJ riL « ¿ r r tr* 
- _ - i j - ■ ; i ; _ _ l _ i _ j - r » r J 
f eift. utr.it-i wi tri- iftrLAtrtrr.' eOiiE dOO Su. ruano 
4. Effective jen fils reproduced! spatial frequency 
)H.. - visual effective spatial frequency, A,- ; - erfec- 
t i ve spatial freque.oey, - - enlargement scale ;• T he 
visual effective spatial frequency has a saxiturn of 
12 Lp/ss. Together with usual enlargement scales up 
to 15 «e get a value of 152 Lp/no which is exceeding 
L;;t L ! T f byivtv Cj I VB/T i Ì $« f rrj 5 wr 
StíV L.::dL Li - T • t : f * • L. 1b Lip lO v:>ib Spalici* r / fcT Q Li tT í • L V » J ,! 
2£Ew , èTS Vi Sudi j V CCS£'?V90 » 
; bLifiiiiii b? 
iibjscti ve/ti ! j& 
.. L. r - V V. - 
b b l tr 
- •■> 
r- c tí I: 9 :s D 0 U ¿ d f. 2 &f; Q > r et Li 5 ¿ S c. : ¿, 
T _ 
ili di Tf fc'LiLifc^L V rtf 
; ; l_ v, ; .• ; c 
_ i ? 1 ; _ ; j. : _ . . . . 1 : . * 
udii i Í $ * Li í ! ^ bptí L1 tíi 
7rom the resulting modulation transfer function which 
15 the link of the modulation transfer functions of 
objective and fils. For two real systems, camera LHK 
from Carl Zeiss Jena with aerial fils VF 45 fro® OSwG 
¡i j , _ __j vr> v ,* t r '-^ 1 - i .:u 
WuiTE'f! dOu Cafterci iva?. *t tf 0» uar i tei ss ae«c wit;? 
aerial film VF 45 fro® OR«S Ho!fen, the system modu 
lation functions with their limiting spatial frequen 
cies are shown in figure 2. 
; ipse) 
? spa- 
"efore 
insfer 
: 33m № 
Air photos show reduced targets. T he reducing scale 
depends on the focal length of the used objective and 
the altitude. It is the relation between target size 
and picture size 
y/y = vh^/f>-i 
fy - target size, y’ - picture size, h g - altitude, f 
- focal length' To get the effective spatial frequen 
cy we had to multiply the true spatial frequency with 
the reducing scale 
Rh=R"iy/y’> 
>lR t , - effective spatial frequency, R“ - true spatial 
frequency, y/y' - reducing scale! 
m 
* VP HS/LhK 
z VF 4 
225