A free tool for the fulldome community
What is parasitic light? The easy answer is any unwanted light which is added to the original image and radically decreases the contrast ratio. In fact, there are many different sources of parasitic light: from the outside (ambient lightning, exterior light leak, phone flash, EXIT signs, etc...), from the black level of the projectors and from the image itself, which we call auto-parasitic light or cross-bouncing. This phenomenon can be seen when the light emitted from the screen is reflected back on pale surfaces. With a flat screen, this problem is easy solved with dark walls, ceilings and furniture.
In a dome this is much more problematic since all the "walls" are white, the light of the image on the front of the dome will increase the black level of the rear and vice versa. It's hard to find information on the internet regarding this issue, so we created this tool in the hopes of helping the fulldome community to have a better understanding of how parasitic light will affect their productions - before seeing it in the dome!
Here you can upload a single frame from your project and our server will automatically simulate the parasitic light produced by the image when projected in the dome and add it to your original frame. In this way, you will have a more realistic idea of the final image quality.
⇒ Keep the background dark.
⇒ For bright footage, try to darken the regions out of the interest area and increase artificially the contrast level.
⇒ Make high contrasted objects.
⇒ Images near the zenith will produce less parasitic light since it emits towards the floor. Try to use this to your advantage by positioning your area of interest on a higher position.
⇒ Of course, use this tool as many time as you like to find the best results.
⇒ You cannot minimize auto parasitic light with more powerful projectors and they "contrast ratio" is far away from competing with this phenomenon.
⇒ Since the effect of light is purely additive, you cannot apply an "anti-parasitic" filter on your image based on the result of this tool. You simply cannot make black blacker than black.
⇒ If you can, keep the floor, furniture and unused screen surface covered with light absorbent material.
⇒ Choose projectors with low black level.
⇒ Keep ambient light low and minimize outside light sources from entering.
⇒ A grey screen should help for auto parasitic light instead of a pure white and it can help to reduce parasitic light from other sources such as ambient light or light leak from the outside.