Let me rephrase...
In shooting menu 2, we are given choices of IS 1, IS 2 etc. If you press INFO in that screen you can then choose 'focal length'. I'm wondering what's the significance of this setting.
It was default at 50mm (I think) but when I use the Samyang 7.5mm, the IS causes the image on LCD to stutter and jump. When I got the lens, I was told to set the 'focal length' in the IS menu to 8mm which stopped the stuttering.
So what does changing this setting mean in the scheme of things? Should I keep it at 8mm or do I change the setting as I change the lens? And what's the point?