foul or not

[Brendan Moore]

Not a foul, as he is not snookered

It is a foul as he is snookered. The cueball is snookered when a direct stroke in a straight line to every ball on is WHOLLY or PARTIALLY obstructed by a ball or balls not on, in this case the black. In this question he can only see a quarter of the ball on, so he is snookered.

[The Statman]

People are often confused about this because they think of "snookered" as meaning like when you've rolled up to a baulk colour.

The meaning here is very specific and is the same as when judging a free ball in the first place.

So basically, when you have a free ball, you mustn't leave your opponent in a similar position behind the ball you've chosen - otherwise that is a foul and ... yes ... your opponent will have a free ball too!

My articles on How to judge a free ball and, more useful in this query, what you can (and can't) do with it may help. There are a few diagrams within these threads which hopefully make sense!