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NIHU ROO UU 
Pinatar 4/125 is provided with a film pressure plate to be 
adjusted in such a way that at a distance of + 7 um from 
this plate optimum image quality is obtained over the en- 
tire image field. MTF measurement revealed that this re- 
quirement has been fulfilled. Figure 2 shows the LTF 
curves of the lenses with the centroid wavelengths 540 nn, 
660 nm and 720 nm (bandwidth + 20 nm). MTF in the image 
field can be improved by correspondingly adjustine. the 
film pressure plate,quality in the image field remaining 
adequate. With optimum focussing in the image centre the 
MTF curves lie in the vicinity of the diffraction MTF. 
Pt On the Lanegon PI 4.5/150 wide-angle lens MTF was measured 
| in radial and tangential azimuth, using different Stop 
values (k, z 4.5, Kj z 5.6, k, z 8) and different wave- 
length radges (400 fim to 700 Hm and 500 nm to 700 nm). In 
consideration of the spectral sensitivity of the second- 
ary electron multiplier illumination was adapted to the | 
Spectral conditions to be observed when taking photographs = 
with the Lamegon (Figure 3). 
Focussing of the lens on to the maximum modulation trans- 
fer factor M (R') in the image centre was made with the 
spatial frequency R' = 15 L/mm, stop value k = 4.5 and 
wavelength range 500 nm to 700 nm. The plane thus ascer- 
tained is also the plane of maximum Strehl intensity in 
the image centre. In this plane the further measurements 
with different stop values and wavelength ranges Were 
carried through. 
The measured results for the spectral range 500 nm to 
700 nm and k = 4.5, 5.6 and 8 illustrated in Figures 4 
to 7 show a good and relatively uniform modulation trans- 
fer over the measured image field, the optimum stop value k 
being 5.6. The wide-angle lens is relatively insensitive 
to defocussing; even with a defocussing of t£ 100 um modu- 
lation transfer is still satisfactory Ponte B). M