Some spells allow the Wizard the option to focus more magical force into their casting, thus extending the effective range, amount of damage caused or area of effect. Where this is an option, it is clearly stated in the spell's effect, as is the extra casting cost required to achieve the additional effect.

Note that if the controlling player does not state otherwise before rolling the dice, a Wizard is assumed to be casting the standard (and therefore less difficult to cast) version of the spell, so be sure to let your opponent know if you're going to attempt a boosted version!

For example, the aforementioned Empire Bright Wizard could have cast Fulminating Flame Cage at a higher level, increasing its range from 24" to 48", but increasing its casting value from 11+ to 14+. If he had wished to do so, his controlling player would have had to declare this intention before the dice were rolled.