I’ll start with a daft question: what does ‘hotlight’ mean? I’m not being snide, I’m puzzled.
I’m fortunate enough to have a good collection of continuous lights as well as flash, so I’ll offer some vague musings on some of the differences – or maybe it is a paean to the fresnel light. Ignoring HMIs and Mini-Flos, most of my continuous lights are Arri Juniors between 150 W and 2 kW, which I regard as the industry standard small focussing fresnel lights. Along with those I have small 100/150 W dedos and the larger 650 W dedos, a 650 W ellipsoidal spot and a few open face lights – variable beam spread blondes (2 kw) and redheads (600 to 1000 W), and fixed beam spread broads (750 to 1000 W) including a few Tota-lights. As an aside, there are people who would prefer us to use the terms yellows and reds because they find offence in calling them blondes and redheads (I guess that it is discrimination against brunettes), but they seem happy with ‘broads’. Pause for a moment to imagine what else broads might be called, and a scene in which they are called that.
Therein lies one of the main differences between continuous lights and flash to my mind – the type of instrument. My choice is based very much on the type of instrument I would prefer to use. The fresnel types, especially their close relatives the dedos, are so versatile and controllable. Even used directly, they act as a nice even round source. (With continuous lights not only can you see what you are getting, you can also stand at the subject’s location and look at the shape and varying intensity of the source - with your sunglasses on if necessary) You can create soft light of the exact quality you want by varying the size and location of the reflected or diffused spot, and by selecting the reflective or diffusive material. You have great versatility in the placement of lights and reflectors in a tight location – a soft source can be as thin as a piece of foamcore and the light itself can be over the other side of the room out of the way, or even outside the room. Reflectors used in that manner are another way round the heat problem. Softboxes and fluorescent light banks are like one-note instruments in comparison, though it may be a very pleasing note.
Fresnel lights lose light into their case, especially when spotted. They aren’t so bad in that respect at full flood, when they approach the efficiency of the brutish open-face instrument. Dedos don’t lose as much light as standard fresnels, thanks to the extra lens. Neither dedos nor standard fresnels are great for evenly illuminating a softbox – they are good at doing it unevenly though, which is often preferable for portraiture. Open face lights do the evenly-lit softbox thing better. Totas are great for that.
While talking about open face lights that use lamps with high temperature envelopes, and especially Totas, I really want to emphasise how important it is to use them with a guard or safety glass, even though you lose light through the guard, and it restricts the maximum wattage (eg 750 W for a guarded Tota vs 1000 W for an unguarded one. A 750 W guarded Tota puts out about half the light of a 1000 W unguarded one). It is very rare for a quarz halogen lamp to explode, but when they do the consequences can be awful. You have only to see it happen once for it to be impressed on you forever. Hot shards of glass come flying out, setting fire to things they pass through and embedding themselves into anything soft, putting little burn marks everywhere. Very dramatic, very dangerous. Totas are especially vulnerable because of the ease with which they can get fingerprints on the lamp envelope – the grease blackens, and the blackened area causes a hot spot with consequent stress from the differential expansion, then bang. It’s a worthwhile demo. Also be aware of the permissible orientations of the lamp and instrument because that affects the temperature distribution and cooling.
None of the above means that you can’t achieve the same lighting effect with flash as with continuous light – there’s always a way, and it’s just a personal preference. The only thing I can think of that really distinguishes the two types of lighting is movement and sharpness. You can’t get motion blur with flash (unless you use it with continuous light) and you can’t usually freeze motion with continuous light in the same way that you can with flash. For me. the main attraction of continuous light is the thousand things you can do easily with a Junior, and the million things you can do more easily with a dedo.
Bob, 6 kW on one circuit? I hope that you realise how fortunate you are. When I came to the USA I learned very quickly that you can’t hang as many kW off a 110 V spur as you can off the 240 V rings that are common in the UK. (“What do you mean - I can’t plug a little 2 kW Junior in?”)
As for fan cooled units, if there’s a possibility of them being used for film or video with location sound, forget them.
Best,
Helen