This was inspired by a reflection on a shop's shutters that I pass on the way to my local. The reflection of the traffic lights showed up as concentric circles of light, which seemed like a cool effect. Unfortunately I lack an attractive model to put next to the reflections.
It turns out this happens in reverse. Parallel light reflect off cylinders as an arc.
I started out with some silver coloured straws (99p home bargains). A parallel torch light (one with a curved lens on the front) shone down their length from a reasonably high angle reflected as a arc. It was a diffuse reflection as the straws were not perfect reflectors and small diameter. I could get a slight rainbow effect by putting a filter made up of strips of colour in the path of the light before it hit the straws. Unfortunately, rainbow colours diffuse together to make white. Changing the angle of the light hitting the tubes changed the size of the arc. If I put the tubes at an angle, the arc stretched out horizontally, which could be was useful. 99p invested. I had found something interesting, time to upgrade!
I found out that you can get chrome plated steel tubes for not much money. They are used for clothes rails in wardrobes. I bought a 1.2 m length of 25mm steel tube and chopped it into 5 24cm lengths. £2.99 invested at Screwfix.
That worked much better. The diffusion went away as the mirror finish created a nicer and sharper arc.
The strips of coloured filter made good colours and it looked pretty much like a rainbow. So I can use them to project a curved band of light/colours..
How about a double rainbow? If you lift one end of some of the tubes, they reflect the light at a different angle, which makes a different arc. You have to play about with the horizontal angles to if you want to make them totally parallel. The shadow on the right is a shadow from the raised tubes on the far right corner.
So then I tried taking something approaching a proper picture with it. It worked. The tubes are between the camera and the subject, the torch was next to the camera and the rainbow was projected around the subject. A normal flash was off to the left lighting the subject. The light was a bit hard to manage because of lack of space; the distance from the camera to the wall was only about 2m.
Would it be easier to just use a projector? Probably if it was programmed with exactly the picture you want. This is easier to adjust as you can change the shape of the arc just by changing angles.
It turns out this happens in reverse. Parallel light reflect off cylinders as an arc.
I started out with some silver coloured straws (99p home bargains). A parallel torch light (one with a curved lens on the front) shone down their length from a reasonably high angle reflected as a arc. It was a diffuse reflection as the straws were not perfect reflectors and small diameter. I could get a slight rainbow effect by putting a filter made up of strips of colour in the path of the light before it hit the straws. Unfortunately, rainbow colours diffuse together to make white. Changing the angle of the light hitting the tubes changed the size of the arc. If I put the tubes at an angle, the arc stretched out horizontally, which could be was useful. 99p invested. I had found something interesting, time to upgrade!
I found out that you can get chrome plated steel tubes for not much money. They are used for clothes rails in wardrobes. I bought a 1.2 m length of 25mm steel tube and chopped it into 5 24cm lengths. £2.99 invested at Screwfix.
That worked much better. The diffusion went away as the mirror finish created a nicer and sharper arc.
The strips of coloured filter made good colours and it looked pretty much like a rainbow. So I can use them to project a curved band of light/colours..
How about a double rainbow? If you lift one end of some of the tubes, they reflect the light at a different angle, which makes a different arc. You have to play about with the horizontal angles to if you want to make them totally parallel. The shadow on the right is a shadow from the raised tubes on the far right corner.
So then I tried taking something approaching a proper picture with it. It worked. The tubes are between the camera and the subject, the torch was next to the camera and the rainbow was projected around the subject. A normal flash was off to the left lighting the subject. The light was a bit hard to manage because of lack of space; the distance from the camera to the wall was only about 2m.
Would it be easier to just use a projector? Probably if it was programmed with exactly the picture you want. This is easier to adjust as you can change the shape of the arc just by changing angles.