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Matt Workman

How to Control a Large Light Source

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How to Control a Large Light Source

http://www.cinematographydb.com/2015/11/how-to-control-a-large-light-source/

 

In this tutorial I share my process for lighting a scene with a large light source and then controlling the unwanted spill.

 

I'd love your feedback on the tutorial and the illustrations. There has been some really great discussions on Reddit and directly on the post.

 

Cheers,

Matt

 

 

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Very good presentation.

Minor correction: "Inside of the lamps are standard Mogul bases that accept standard tungsten house hold light bulbs or globes."

 

Table lamps and most ceiling fixtures (in the USA) use medium base sockets. You usually want table lamps on a hand squeezer (household dimmer). A spray of black tips n' streaks temporary hair color can be applied to the bulb to cut some or all the light from the top or side of the globe.

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I've actually noticed a lot more CFL and LED rather than tungsten installed in the standard fixtures these days. They render the hand squeezer unusable. I have a few tungsten and cree LED's that are dimmable that I usually wind up switching out bulbs with. Nice tip with the tips n' streaks!

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Is there a way on how to block light without having to buy a lot of stands for the flags? I want to achieve dramatic low key lighting without having 10-15 stands for flags. Thanks

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Not really. The larger the source for the softer the light, the larger the flags have to be. Generally each flag needs a stand. A large diffusion frame usually needs a stand on each side unless you just create a "T-Bone" rig with the diffusion hung from a cross pipe held in the center with a c-stand.

 

The only alternative that doesn't require extra stands are the soft egg crate "light control" grids you can stretch over a diffusion frame, which will reduce spill forward of the diffusion frame, though you may still need flags behind to control spill around the sides of the diffusion frame depending on the source and whether barn doors are enough to get rid of any spill beyond the diffusion frame. And even an egg crate grid isn't going to as dramatic of a cut compared to a large flag even farther from the diffusion frame.

 

If you put a soft egg crate grid on a Chimera, then you can eliminate some stands:

 

http://www.filmandvideolighting.com/fabricgrids.html

http://theclosefocus.com/lighting-control-grids/

 

But you are limited as to the size of the soft light. A Chimera can only be so large before it basically is too big to hang off the front of a light.

 

The smaller the light and diffusion frame, the smaller the flags, to the point where a hard fresnel lamp can be cut with just the barndoors.

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Stands are the expensive part, it's true.

 

I have got quite a bit of mileage out of very low-cost stands like these, which are terribly flimsy but somewhat usable indoors. You can string bits of polystyrene board (painted black one side, white the other) between two.

 

They're terribly breakable - don't extend them quite all the way, otherwise the tubes don't cross over and it becomes incredibly easy to snap off the little plastic clamps. That said they are very lightweight and quick to rig. Just don't use them outdoors in anything other than a dead calm, because they'll be shrapnel after the first fly's fart of breeze.

 

P

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Aren't the top and bottom flags almost just matting the diffusion frame. On the website the rational is given, that a big sorce big diffuson screen plus mesh(s) give the DoP options to bump the lux if needed. The small budget, indie, art film thinking goes straight to the thought that a 2K blond with a smaller diff frame could light that scene quite well.

 

@phil

If you are patient, decent used C stands will pop up. In NZ they are like hen's teeth, but four just sold on local online store Trademe for NZD100/each (50 English pounds/each).

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What I've seen in some photography studios is that instead of using 4x4 floppies on c-stands, they will use 8x8* white/black showcards folded in half as self-standing large flags. They can be flipped depending on whether you want a solid white or black reflection. It works great for product photography where you don't want to see the metal edges of a flag or diffusion frame reflected, and they are very easy for one person to move. The downside is that they are large and difficult to transport and store. That pretty much limits them to studio use only.

 

*The ones I've seen may have been 4x8, which is a standard size. Not sure if you can easily get 8x8, just FYI.

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@phil

If you are patient, decent used C stands will pop up. In NZ they are like hen's teeth, but four just sold on local online store Trademe for NZD100/each (50 English pounds/each).

 

with gobo arms, clamps.

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Stands are the expensive part, it's true.

 

I have got quite a bit of mileage out of very low-cost stands like these, which are terribly flimsy but somewhat usable indoors. You can string bits of polystyrene board (painted black one side, white the other) between two.

 

They're terribly breakable - don't extend them quite all the way, otherwise the tubes don't cross over and it becomes incredibly easy to snap off the little plastic clamps. That said they are very lightweight and quick to rig. Just don't use them outdoors in anything other than a dead calm, because they'll be shrapnel after the first fly's fart of breeze.

 

P

 

I got these sorts of stands with a very cheap 'lighting' kit a while back... If one's 'expectations' are not great, as was the case with me... they work...

 

I'm also thinking about doing a DIY clip on using PVC piping from Home Depot or similar consumer building supply outlet. For my day job I had to construct a stand to carry a 50 lbs antenna at a testing lab... amazing what they didn't have for equipment... and had to run to Home Depot for materials...

 

While such stands may not fit with a 'pro' looking set... they would work for people on a Nolo Budget project.

Edited by John E Clark

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010.gif

 

How to Control a Large Light Source

http://www.cinematographydb.com/2015/11/how-to-control-a-large-light-source/

 

In this tutorial I share my process for lighting a scene with a large light source and then controlling the unwanted spill.

 

I'd love your feedback on the tutorial and the illustrations. There has been some really great discussions on Reddit and directly on the post.

 

Cheers,

 

Matt

 

 

Question Matt. Why not just use a smaller diffusion since you arent really using the entire diffusion as shown. Wouldnt that be easier? Wouldnt you still get the same result?

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No because the flags aren't right up against the diffusion frame. If they were, then yes, you might as well use a smaller frame and no flags, but being out a few feet mean that they are cutting the light spill off to the sides more while directing the soft light more in one direction.

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I had the same thought as Jae. I don't know if we will see a difference with the smaller frame, (a smaller source on a smaller area of diffusion).

 

I was hoping Matt might drop back in and show another simulation of just that. But this little issue is sort of ignoring his topic...How to Control a Large Light Source.

Edited by Gregg MacPherson

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I think one can imagine the difference in spill and fall-off if there just a smaller diffusion frame where the square hole in the flags were, with no flagging.

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In my imagination I just swapped out the diffusion screen and source, leaving the flags in. One could swap the flags for smaller ones in the real world. Why were you suggesting no flags?

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Because Jae's question was why not just use a smaller diffusion frame rather than flagging a larger diffusion frame, because the animation makes it look like you just squared off the large frame into a smaller shape.

 

If you put a smaller diffusion frame behind those flags, it would be a little less soft. You have to think three-dimensionally -- if the subject steps forward or back a little, they can still be hit with light from the larger diffusion frame behind the black flags, from their perspective because of the angle of the light.

 

If he animated this from a direct overhead view to show you the degree of spread, you'd see this if you switched the size of the diffusion behind the flags. From an overhead view, imagine a slit that represents the black flags and imagine two different sized sources a few feet behind that slit. The larger source is going to spill around the slit more.

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Why the assumption that the flags are removed? I don't see it in Jae's question. Why would anyone do that?

Yes, if the "girl" steps a lot closer to the diffusion frame we will see some change due to light that was otherwise headed to the ceiling or floor. Just as she exits the widest possible (camera) frame, assuming a lens change or camera shift.

 

Apart from this extra spill that is leaving the diffusion screen at an acute angle, what difference in result is there between the different sized screens, given the flags are there? But of course, I bow to your experience.

 

But this is all fun in a teacup, not relevant to Matt's idea.

Edited by Gregg MacPherson

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Question Matt. Why not just use a smaller diffusion since you arent really using the entire diffusion as shown. Wouldnt that be easier? Wouldnt you still get the same result?

Don't you think the "wouldn't it be easier?" question is in reference to the large amount of flagging? He's assuming from the animation that the flagging is cutting down the size of the diffusion area but that's because he isn't noticing the space between the diffusion and the flags.

 

Again, you have to think three dimensionally. If the subject standing there can see more of the diffusion frame behind the flags from their position, then it means they are receiving a larger area of light than the shape of the square hole in the flags, and therefore the light is softer than the size of that gap in the flags. If you shrank the size of the diffusion and the subject could see that the diffusion frame was smaller from their position, then they would be less softly lit because the size of the source would be smaller. The animation is confusing because it is a 3D animation presented in 2D from one angle. As I said, if he created an overhead view with software that simulates the spread of light, you'd see that the larger source is still hitting the subject from a wider range of directions and therefore is a softer source.

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Here's a crude drawing of swapping out the large diffusion frame behind the gap between two flags with a smaller diffusion frame:

soft_flag.jpg

As you can see the subject from their perspective can see more of the large diffusion frame behind the flags and therefore is receiving light from more directions, thus getting a softer light on their face.

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I think "easier" refers to downscaling everything. But, no reasonable person would automatically remove the flags, so that line of thinking is not so interesting.

 

As you say, there is a small band of diffussion screen hidden by the flags that contributes something to the subject. For her face the band is like 8'' wide at the top and 6'' wide at the bottom. So, if one was fussy and thinking three dimensionally, just size the smaller diffussion frame to that. Or consider the value of that contribution and perhaps ignore it.

 

The fun in a teacup diversion was about whether one could get the same look with a smaller diffusion frame and smaller source.

 

Sorry to Matt if he's dissapointed in that spinoff.

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I don't see why just making everything a little bit smaller is less work, it's the same number of stands, flags, and diffusion frames. You could make it significantly smaller to make it easier but then it's not the same effect. To get the same softness you'd have to move everything closer to the subject, and then you'd have a greater fall off in intensity with distance from the source.

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Our last post crossed in the ether. Your flags in the drawing are a long way away from the diffusion frame, which illustrates your idea very well.

 

But in Matt's simulation, the top and bottom flags are a bit over 2' from the diffusion screen. Left flag front edge similar? OK the right hand flag front edge is 5 or 6'.

 

So your drawing illustrates a principal, but not how that principal is applicable to this set, setup. Actualy it's missleading. As I said before, the hidden band on the big diffusion screen at the top and bottom is quite narrow.

 

Looks to me like the smaller frame would be about half the size so the lamp would be about 1/4 the size. That's not "a bit" smaller.

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But no getting away from the physics .. if its all smaller.. maybe even you could get a short gaffer.. you will have to move it all closer to the subject to get the same softness of light.. which effects your wide shot.. and how much the subject can move around.. so its not the same setup..

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