Making A Rainbow

How would I create a rainbow in my shot? In my bright daytime scene under a veranda during a downpour I would love to make a natural rainbow.

My trusty Dictionary says a rainbow is "an arc of all seven spectral colors appearing in the sky opposite the sun as a result of the refractive dispersion of sunlight in drops of rain or mist."

Does that mean if I blast a beam of light from over the camera can I place a rainbow where I want it? Controlling the size, intensity and location of the light on the rain and mist should make it possible to control the rainbow, right?

I could have sworn I saw it done on the X-Files...

Kevin M. Andersen

Finally, a question on cinematography, I was getting tired of this my video is better than you video 'pissing contest'. It seemed out of place on a cinematography site.

To answer your question. I had the opportunity or should I say the job, of recreating a rainbow for a shot in the early morning. I used the sun to do this on an early morning in Colorado. August is summer in Colorado, and I noticed that my sprinkler would give a rainbow if you stood just right as the sun came up over the east. I tried to recreate this effect and it was very, very difficult.

We were in college, so we were willing to try anything, unlike our professional work, which must be now what we 'know' to work.

I tried lights, I tried all sorts of hoses and sprinklers but we ended up going to the source. The sun was the light source coming over the east, the sprinkler head is a simple type, metal cap with a slit on top of it, and the time is as soon as the Sun comes up. The sun was moving, so we had to re-adjust the sprinker often.

Which begs the question. What time do you intend to shoot this? What is your light source?, how long do you intend to shoot for?

As for the photography, don't worry too much about it. If you can see it, you can film it.

Hope this helps.
Jesus M. Medina

How about a glass shot? I releber a shoot I worked on a few years ago when the main unit did just that. It was of an aeroplne flying into the rainbow. I seem to remember it worked quite well.

Which these days opens up the whole idea of doing it in post.

Brian Rose

How about this for a Bizzarre idea.

FILTERS.

I think Cokin makes a Really Cheesey ( my apologies to Cokin for Cheesifying them) Rainbow filter, that You could Maybe Play with. Or I think Tiffen made a Rainbow Filter that would Colorize Strong flares. Mine came out of the Dollar box and has the weirdest separation that snakes through the filter. Or perhaps you can call up Edmund Scientific and see about some Diffraction Grating.

Steven ( stop me now before I suggest a light coating of Oil and water on a Clear filter) Gladstone

I was going to make this suggestion as well (and I fully agree on the cheese factor). It was my understanding that you needed the rainbow to "appear" in shot. A simple approach would be a wide lockoff with and without filter and dissolve the two in post. I wonder if something more believable couldn't be done with a 50% percent mirror and some type of illuminated "rainbow" reflection (perhaps projected or a transparency). YOu could then make it "appear" by turning on your light source or removing a solid that was blocking the reflection. Sacha Vierny uses a similiar gag in the Kodak Series "Shooting for Fantasy" to make a magical beam of light appear in shot.

If staunch realism is your desired goal I'd sooner reach for the plaid filter than a rainbow!

Regards,

Jonathan Belinski

I remember in an old A.C. article about the Lightflex, inventor Gerry Turpin suggested using a rainbow pattern created with gels in the Lightflex filter holder, which would then reflect it over the image somewhat out-of-focus.

Wouldn't work with the new VariCon but could be done with a simple 45 degree piece of glass in front of the lens...

David Mullen

Yes, thanks to all who suggested ways to cheat rather than recreate. The narrative of my story would be enhanced by the subtle insertion of a small rainbow pattern which is revealed when a character moves in a two shot. I'm talking subtle, not 'fantasy' or anything that will jump off the screen. It is an additional visual element I want to add at this moment and must be done in camera without any post tricks. It has to be seen in depth, in the background rain and mist so filters or projection of some kind would not be useful.

In order to recreate a rainbow one must understand what conditions are necessary to create one. I have heard many people tell me they see them by accident. Are the physics of this just so precise, the requirements so tight, or the conditions so extreme that this is not possible?

Lets try to refract some light in an artful manner!

Kevin "there will be gold at the end of the rainbow if I can do this" Andersen

>In order to recreate a rainbow one must understand what conditions are necessary >to create one.

From an airplane looking down to the ground I'm told a rainbow will be a circle and not an ARC. I think the idea presented about using a piece of glass at a 45 degree angle would work best. The further away from the Glass the rainbow painting ( On a Black background) is the deeper it will seem in the background.

Steven Gladstone

>I think Cokin makes a Really Cheesey ( my apologies to Cokin for Cheesifying >them) Rainbow filter, that You could Maybe Play with.

You know I carried that Cokin rainbow filter with me for years

Never used it.

After at least ten years I took it out of my filter kit.

The next job I needed it.

Cheers

Geoff Boyle

>In order to recreate a rainbow one must understand what conditions are necessary >to create one.

OK we know you need a light source and water vapour for refraction. Jesus (Medina) said he had trouble recreating this with anything but the sun; but even if you can find a light source strong enough, will it give you a full colour spectrum? ie: if using Tungsten/HMI/Arc etc - will you get the same spectrum?(refraction of white light and all that...)

Sorry Kevin, I know this isn't helping you much - I'd try it out with the abundant sunlight you have in LA and a hose or sprinkler and suggest talking to a SFX house about using rainpoles to make the mist since this will be easier to switch on and off than the sun! You'll have a relatively short window of sunlight position but think yourself lucky that you're not trying this in London!

Whilst I agree that you can photograph what you can see, we all know that the eye does not see the same as filmstocks - I have always had great difficulty making rainbows appear as strongly on film as they do to the naked eye. Even when they are strong enough to make a clearly visible double rainbow, the second one hardly registers on film against a dark cloud background - perhaps a lighter background is better but I don't believe so. Anyone know?

What are your reasons for not wanting to do it in post? It seems that you would have the control you need far more easily this way... I've sometimes found that a contrived reality is more realistic.

For Steven :

>From an airplane looking down to the ground I'm told a rainbow will be a circle and >not an ARC.

Also available on mountain peaks above the cloudlayer, this is known as the 'Brocken Spectre' - when you are between the sun and the clouds you get a shadow surrounded by a full circle rainbow, not much use in this case since clouds are hard to form at will. :-D

Dan Blanchard

>I have always had great difficulty making rainbows appear as strongly on film as >they do to the naked eye.

Just speculating - but I wonder if the fact that rainbow light is monochromatic - a single wavelength at any part of the 'bow - (compared with most other objects which reflect a broadish spectrum of wavelengths) makes it less successful at recording on colour film to match the way that we see it.

>perhaps a lighter background is better but I don't believe so. Anyone know?

Speculating again, but I think a lighter background would desaturate the image and make the rainbow _less_ visible. What I have noticed in photos of rainbows, is that the sky appears much darker outside the 'bow than inside ( I think it's that way round). This is never so obvious to the naked eye, but it looks very convincing - possibly a necessary feature if you did the shot artificially.

Dominic Case

With all the minute details of water droplet size, and so on...might be better to go with the recommendations to do it in post.

I think one only sees rainbows with the sun behind you. In other words : rainbows are frontally lit for the viewer. (At least really strong, long-arced rainbows).

In other words, don't even bother side/back lighting a man-made water-mist. I don't think you'd get much of a rainbow that way. Hope that suggestion wasn't too obvious.

They also occur "easier" further away from the viewer. When we see rainbow diffraction close to us, we only see part of the arc. Seeing the full 180 degree arching rainbow occurs further away (less parallax error between the viewer and the sun).

Someone recently told me of a location scout, whereupon the director saw a rainbow and ordered the driver to head to the end of it. Problem was that the director was serious. The shoot could only go downhill from there.

Mark "hey, front-lighting isn't always bad" Doering-Powell

A rainbow painted in the proper perspective against black, mounted in a blacked out "tent" with it's own light source would work fine with a partially silvered mirror. Make sure the BG that would be behind the effect is predominately dark so it reads well. Watch out if you want to fade it up using a variac though, the color temperature change of the brightening bulb would make the spectrum fade up from mud. There are other ways of brighten the image, but I might suggest a clever black card art wipe.

Eric Swenson
Somewhere over the H20 droplet light diffraction

Saw this for a second time a couple of weeks ago on a boat off the island of Maui. Hard to shap a shot of it as you are looking at the sun. A dot on glass would have been nice.

Got a nice shot of my hand in the way though.