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Mirrors to control sun light

Boris Kalaidjiev

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Hi everyone, 

I have an upcoming shoot in Malaysia, pretty near to the equator so the sun is mostly high and bright in the sky and I am thinking of ways how to control the sun without fighting with it. 


I have a scene where I have an air-well (hole in the ceiling) that allows sun light to come straight down, but I would like to be able to control the angle of the light falling on to the set. Do you think its possible to do this with 2 4x4 mirrors so that I can take advantage of the sunlight throughout the whole day and control its direction coming on to the set? I have done bellow a small crude plan of what I mean. Theoretically I guess it makes sense but practically I have no idea if it will, has anyone tried something like this before and did it work? 

In the plan bellow I have numbered 2 diffrent set-ups: 

1) If we have nice direct sun light and no clouds.

2) If the day is cloudy and there is no direct sunlight. 


The plan bellow is not up to scale the height between the air-well and the subjects is probably 20ft. 






This is the effect I am hoping to achieve with the 2 mirrors.




P.S We are planing on building our own 4x4 mirrors any tips would be much appreciated as I really haven't worked with mirrors that much.


Thanks a lot! 


Edited by Boris Kalaidjiev
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Hello Boris,

I've never done a mirror into a mirror for more than a few minutes at a time. I can see a few issues.

You know a guy will have to remain up there to adjust the sun-collection mirror. Something like every 3 minutes. Make sure they have a radio and perhaps a timer. It's best to call for another re-aim just before a take. I'd call for it right after camera rolls.

Also, as the collector follows the sun, its angle to the second mirror will change over the day. The steeper the angle, the less light will be reflected. This will manifest as a thinner beam and less bright. This is only an issue if you need that exact look the whole day. But something to consider if the reflector is placed in a way that will have a steeper angle by shoot time. If you move the collector for a better angle, it will affect the beam angle transferred below.

Be sure to plot the sun's arch so the topper's placement doesn't cast a shadow on the sun mirror.


Practically, I see it as a pain in the arse. If I had the option, I'd forego the sun collection and use the M40 lensless and laserbeam it into both mirrors, or avoid mirrors altogether. This saves the headache of adjustments and loosing a guy all day. The photometrics of that light will tell you what lux you'll get on full spot without a lens. All you need is the distance. If the lux at that distance isn't near daylight (80,000lux) then you will need more wattage or dealt with it being dimmer than real sun.

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I forgot to mention. Of course, this is really dependent on the shots too, and you're needs. I can understand the desire to work around bigger rentals or gear limitations.

If you can get the wide shot perfect with mirrors, then when you move the camera in, the beam doesn't have to stay consistent. People won't notice a change if you have to wiggle the mirror. I adjust set lights all the time for camera angle changes. No one notices.


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Hi Stephen, 

Thanks a lot for the detailed explanation. I really do see your point of this set-up being a pain the arse if you had to adjust the mirrors so often. I really wasn't expecting the sun to be moving to fast but I guess if you want the best beam falling onto the collector mirror its good to check before every take. I think I will probably stick with only the second mirror and the M40. 


Thanks again!! 

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