Controlling soft light


New member
I am third year cinematography student.
I like to try different lighting tehniques in the school's training studio.

My biggest problem always is controling the soft light. For example, a key source through 4x4ft diffuser throws light in any direction, including the background wich I want to be dark. I try to use cutters and black flags but they either don't work or in case they do, they are in the frame. I quickly become very nervous about this.

Could you please give me an advise?
Dian Zagorchinov


The easiest way to keep your walls dark is to simply paint them darker.

Obviously this is not always possible, especially on lower budget projects.

One rule of thumb is to always cut the light after the diffusing material. For example a situation I had on a music video recently: A 10k through an 8x8 frame of 1/2 China silk. The idea is to walk the 10k far enough back to fill the frame. This means I am now cutting an 8x8 soft light. All cutters must be placed in front of the 8x8 silk to be effective. To cut this off of walls, etc the grips were using nothing smaller than 4x4 floppies.

I find that the actual placement of a soft source can be more pivotal than cutting the light. Generally, because soft light gets on everything, and has a wrapping quality, you can diminish; if not forgo entirely your fill.

Bounce light for me is the hardest to control. For instance bouncing off a wall or something can be hard to control.

There are tons of tricks devolved over time to cut large soft sources. Large teasers being very common. All these large soft sources take up a lot of room. This is partially why Kinoflos have become so popular, you can have the 4x4 Wall O Light in a small space, and have a 4x4 sized source with very little depth.

It is hard to give a lot of advice on cutting to you because I have no idea as to what units you are using (frame, or clipped to the light, etc) thus its harder to give advice.

". . . including the background which I want to be dark . . ."

Sounds to me like you need faster fall off from your source. This cant be achieved by cutting. If you could place your source higher, and tilted down, this may help keep it off the background. Try walking your frame back, but remember if you go to far the source becomes hard(ish) again. A heavier diffusion material could work better as far as fall off goes. Or you could try to make hard light work, and then really control it if nothing else works (I tend to favor hard light, or at least harder light when its suitable). Also you may want to use negative fill. Drape all off screen areas that the light hits (floor, walls, etc. Just look where the spill is) in black. This can help. A gaffer friend of mine would pump a large unit through a black silk (rather than white silk) to help with the bounce back issues (this is extreme, but almost worth the trouble just to see people's faces when using a 6x6 frame of black silk with a 12k ponding though it in a small interior . . . but it can look really good).

Kevin Zanit


New member
Thanks Kevin,

I have to try with bigger cutters next time, last time I had only one 4x4. I was using a 2K through 4x4 216 frame put as close as it can near the model. I wanted a side modelling light for half face effect without fill. Maybe the problem with the lit backgroung comes from the fact that the training studio is not very large.

I've noticed that the light bouncing back from the diffuser (not the transmitted light) can be a problem, maybe this is where a softbox becomes more usefull.

I'll try some new things next time in the studio.
Dian Zagorchinov


New member
Your problem is very easy to understand. A soft light is an extended source, that lights in many directions, while a spot light (fresnel) is a directed source.

When you try to cut a large source, you actually don't realy cut it, it's more like if you would reduce it's surface, then it's luminance.

If you cut a directed light (fresnel), it works because you can have deeper shadows with such sources when you cut them.

this is why cuting large sources is definitlya pain in the ass.

When you work with large sources, large cuting materials, and put them far away from the scene, it's like you're trying to turn this large source into a small one, compared to the set's dimensions.

trying to have a soft light and contrast beetween the foreground and background is a little bit contradictive, somehow.

This is why it is so difficult, and it becomes hardish. Only great dops with help of great gaffers and grips, like Mr Zanit can handle this work.

It's a very satisfing thing if you can get thru with the help he gave. But if you want to spend less time on this, why don't you try to go on with sources that may give the work easier ?

One consideration about the set is also that if you have the background as far as possible from the comedians, it would be of great help (it helps you to set counter lights, as well, if desired).

If you light the major part of the scene with fresnel lights, even with diffusion on their barndoors, you might get a stronger contrast beetween backgroug and foreground, as you will be able to cut them easier, and if you want the light to be kinda soft on the comedians, well, put the sources that especially light them as close as possible from the camera axis for non moving shots.

A nice device to have a soft light on the comedians while having contrast beetween foreground and background if you have a tracking shot, is to put a "basher lamp" on the camera or dolly in the camera axis, wich is a small soft light that will always remain in the axis. Doesn't work all the time, but sometimes does (mind it's not too strong as we don't "feel" it).

(my idea was only to be quick with soft light on the comedians, and contrast beetween background and foreground, with ability of cuting the set keylight)