TABLE 4 
Studies on Scale variations on micrographs 
  
  
  
  
Magnification 
Nominal Actual Average Variation Percentage of Variations 
(Max - Min) from average 
1200 1262 11.6 +0.46% 
1800 1899 3.5 +0.10% 
2700 2804 19.7 +0.35% 
4200 4351 3.1 +0.04% 
6000 6135 58.0 +0.47% 
9000 9183 91.2 +0.50% 
12000 12298 182,2 +0,74% 
Average: +0.38% 
  
This study draws two important conclusions: 
A. The average range of scale variation for the micrographs from this SEM 
is +0.38%. Earlier studies with older EM systems indicated higher 
values (e.g., see Ghosh and El-Ghazali, 1977, where the corresponding 
value for another, older, SEM was +1.17%). This indicates improved sta- 
bility in the EM systems and in the power supply situation, now-a-days. 
B. The image rotation does not change with magnification as much as has 
been noticed in previous studies (e.g., Ghosh and El-Ghazali, 1977, 
reported steady change from 6° to 53° for magnification change from 20 k 
to 100 k for a TEM). May be, the larger rotations are peculiar only to 
the TEMs. Nevertheless, this aspect is worth studying. This may also 
indicate that we are using better and more stable EM systems. 
Further continuous studies on these lines are in progress. 
The author wishes to thank Mr. Muzaffer Adigüzel for the strenuous ob- 
servations in the photogrammetric laboratory. Dr. M. Krishnadev and his 
associates in the Laval University Department of Mining and Metallurgy kindly 
provided the necessary micrographs. The research has been partly supported 
by the Project No. A1177 of the Natural Sciences and Engineering Research 
Council, Canada. 
References 
Ghosh, S.K.; 1980 "Future possibilities of precision mapping with Electron 
223