Stanbo gives good advice on measuring IPD in the post above. I'll add that I've found it very convenient to make a template for setting the IPD quickly, as it takes the trial and guesswork out of the procedure. I have simply cut a slip of semi-soft plastic to the exact length of my IPD distance, and use this as a ruler of sorts to set the distance between left sides or right sides of the eyepiece lens (which is constant, unlike the eyecups which can wobble a bit).
More specifically on the minimum IPD of the Canon 10x42 L IS, it is 56 mm, i.e. it can be set quite narrow. But you need to be forewarned that since the eyecups are huge and have flat front surfaces and sharp edges, there will be little or no room for your nose between the eyecups if you have narrow IPD. However, if you keep the eyecups twisted in and lean the eyecups against your brow, with your head slightly tilted down, you will get a fine view and good support. Actually, this is what I mostly do even with my 66 mm IPD as it is more comfortable and allows for very quick acquisition of best image and optimal eye-relief distance.
On the topic of 8x and IS, my view is that most birders think they don't need IS at such a low magnification, but after becoming accustomed to stabilised 10x views I personally find even 7x hand-held images tediously shaky despite having relatively good arm strength and not particularly trembly hands. Also, simply placing an 8x binocular on a tripod or some other solid support and comparing the views to freely hand-held views is a rather eye-opening experiment.
Kimmo
