First off, Par cans are not scanning heads, so two different things. Different purposes. Par cans are in a sense light effects, but more lighting than effect. The moving heads/scanning heads/moonflowers/lasers and such are more effect than light.
So that is distinction number one. You use cans (or flats these days, who needs the extra volume if you don’t need the 70s look) to create (colored and changing) light, you use effects to create special, well … effects! And you use a healthy bit of smoke or haze to increase the effect of effects :-P. Cans you can use all night, effects should be used with discretion. Running that 1-pattern laser all night is not gonna be very impressive, just like strobing everyone with every track is not gonna make you any friends. Like with music, you use effects here and there, not with every track/transition. Same is true for lights.
As far as fast-changing, any LED is faster than the traditional bulb-based can when it comes to intensity and color change. What determines how fast it actually DOES change is the controller or controller software and the programs that you select.
Obviously you’d want slowly blending and changing effect when playing something nice and intimate, you’d want headbanging, near-flashing, full-out light changes when doing happy hardcore!
Regardless of the brand you choose (there are quality differences for sure), LED should always be fast enough. You can pick fixtures that have enough light output (in Lumen). I would strongly suggest, if you do want to use lights, to get – at least – four to eight fixtures, two to four on either side on a stand with T-bar. Not only is it the cheaper to buy two usually than to get one with double the power, but you get much more flexibility in setting up your light show. Two fixtures can only cover so much room. 4-8 you have a wider choice in aiming them to cover an entire room.
Be aware that cans come in flood and spot variations. Floods are wide-angled and used for uplighting, stage lighting and general lighting purposes (lots of light in all directions). Spots on the other hand have rather narrow beams and can be used to emphasize something (like a singer on a stage, the DJ 😎 or a big tree in the middle of the venue for example).
So, Grasshopper, light is not something to be taken lightly. As I said in another post on lighting (might wanna read that one too if you haven’t yet), in my opinion DJs should not aspire to be light guys, just as the other way around is not happening a lot. But, if you feel you must do it all yourself, be aware of the choices and try making the right ones to fit your purpose.
Greetinx,
C.
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