Field of view and true magnification of Canon binos

Here are my measurements.

Canon 18x50 IS:

• The apparent field of the bino is 62 degres (from Polaris to over Alpha And).
• The real field is 3.85 degres, measured to be midrange from Delta Cas to Gamma Cas (3.60 degres) and Delta Cas to SAO 11444 (4.13 deg).
• Thus the real magnification is 62/3.85 = 16x, not 18x !

Canon 10x30 IS:

• The apparent field is 48 degres (from Polaris to M31).
• The real field is 6 degres (from Beta And to 2/3 between Mu And to Nu And).
• Thus the real magnification of the 10x30 IS binos is 48/6 = 8x, not 10x !

I wonder if this is standard practice among bino manufacturers ?

How does the Canon 18x50 IS binoculars compare to the 10x30 IS ?

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After searching for years (literally), I was finally able to pick up a good deal on Canon 18x50 IS binoculars out of EBay (thanks to the cheap $!). I have been using the smaller 10x30 IS for 7 years, and always found them very good. But I wanted (of course) bigger magnification, and more brightness.
Here are my impressions after a few weeks'use.




















The optical quality is near-perfect, no problem even on the edge of the image. The stabilization is very good, better than on the 10x30: it starts faster, in less than a second images are rock solid. The button is of the "press to start, press to stop" type : no need to keep it pressed as with the 10x30, this is very convenient.
The eye cups are not as good though. They are too big, and don't fit my eyes, I had to remove them. The 18x50 IS are much heavier than the 10x30, but they are perfectly manageable.

The magnification gain is amazing. I am now able to see much details in passing airliners, that I was not able to see with the 10x30.

The brightness is on par: I can see stars of magnitude 10.5, while with the 10x30 I was limited to 9.5. This indicates they are 2.5 brighter, which is consistent with theory (50*50/30*30 = 2.8).

Watching the moon is amazing: it appears as a big 3D ball. Much details can be seen, such as Mons Pico (even with no shadow), a mountain range only about 20 km wide.

The image hand-help is the same as on a tripod, this is simply amazing.

From time to time, the image appears a little bit blurred or fuzzy. This is probably due to high-speed vibration in the image, caused by the shifting lens correcting shaking. As magnification is high, it is visible from time to time.

On a tripod, with stabilization on, the image appears to slowly drift in one random direction, for about two seconds, than reverses direction, and the cycle starts again in another random direction. I would be interested to know if other owners experience the same thing ?

Overall, these binos are amazing.