# Light spillage -- how much with FP?



## MikeSp (Aug 15, 2006)

I have read where the back wall behind a FP screen should be painted black in order to avoid seeing any light spillage from the FP. (Also read where the back wall should be some pure neutral color that does not add color to the image on the screen and potentially take away from blacks on the screen when the eye compares the blacks on the screen that may appear grey as a result of a black wall).

QUESTION-- IF there is light spillage from a FP, how much is there, i.e., how far out from the screen does the light spillage reach? Will the 3 inch fuzzy surface of a good screen frame take care of the light spillage or how far away from the screen could light spillage occur?? Thanks

Mike


----------



## <^..^>Smokey Joe (Jun 29, 2007)

Ok I have seen some posts of some who go that far, painting all and sundry black.
Not very attractive, my wife would be tapping her toes, hands on hips with a soar impression on her face.:teeth: :hide:

Actually you don't need to go that far.
Medium to low tones is as far as one needs to go, but they must be neutrals and flat(absorbent) in nature.

The reasoning is simple really. All light to our eyes is the total result of all reflections. So if you painted the walls a bright colour, the wall will be iluminated from the screen reflection. The colour will interfare and skew how you see the screen colour. This is because we base what we see in judgement or comparison of the adjacent colour.

The screen colour may change if those wall reflections actually return to the screen itself. The level is usually very low even with highly reflective material about.

The basic problem with brighter colours and even white neutrals is that they can be distracting from the screen glowing with the same intensity. If they are bright and non neutral they will glow and skew your perception of the image colour.

Lighting
Our iris opens automatically based upon the amount there is. A trick to make screens appear to us as having deeper blacks is to add lighting behind the screen, lighting up the wall area. What this does is close our iris, lowering the amount of light we gather and effectively lower the black point for us. 

The edging you question, the borber, is really to define the edge of the image and by being black or felt or anything absorbent results in a contrast to the image.
Sometimes when ppl turn off overscan edges of the image can be uneven, the border will tidy this up. 

How far will light go?

Forever if there is nothing in the way. How far is a star away?
Objects will absorb and reflect, enough objects and eventually all light(radiation) is absorbed.


----------



## MikeSp (Aug 15, 2006)

<^..^>Smokey Joe said:


> Ok I have seen some posts of some who go that far, painting all and sundry black.
> Not very attractive, my wife would be tapping her toes, hands on hips with a soar impression on her face.:teeth: :hide:
> 
> Actually you don't need to go that far.
> ...


IF I painted my HT room black, I would never get to see the effect since I would be gone -- absolutley NO WAF there.

Speaking of how far a star is away, tonight is the peak of the Perseids -- thanks for indirectly reminding me.

Regarding the iris functioning of our eyes -- in addition to what you stated (of which I have no disagreement and have a reasonable understanding) a modern thought expressed by my favorite HT/audio store that does lots of custom installs, is that medium to light neutral tones produce more pleasing results since a medium tone is the average of the tones on the screen in terms of darkness and a totally black or dark painted room means that the pupil of the eye will be opening and closing much more than with medium neutral tones. Interesting thought, no?

Cheers,

Mike


----------



## <^..^>Smokey Joe (Jun 29, 2007)

Yes very interesting.

Actually, light stress is something I am familiar with. It is something quite often forgottern about, like general health at times.

The reality is, as reported by a white paper about the biological effects of light flicker at 50hz (flourescent lighting with magnetic ballasts) is that it does effect biological patterns greater than first thought.

Simply, although we don't directly see flicker, our brains do respond. The response is that our brain cannot decide if it is day or night and the effect is that we alter our hormone production patterns.

Typically cortisol levels are raised, which is the daytime hormone and stress hormone. When people suffer stress related problems raised cortisol is common.

Since that report in 2003 alot of government depts around the world have been changing flourescent lighting ballasts to high freq types(20000hz). You cannot buy magnetic ballast types now.

The problem here is the workforce in office and factory buildings with little natural daylight. 

For the home and home theatre Lowering light stress by getting light levels right is good for you. Calibration could possibly have health beneforts.

Something worth thinking about.


----------



## mechman (Feb 8, 2007)

Just a simple response here, I'm no smokey!! :bigsmile: The three inch border is more than enough to absorb an over spillage. The last time I looked at mine and used a white sheet of paper to help, I had maybe a half inch or less on one side. That may be due to the fact that I'm using a DIY screen which I built myself or it could be due to the pj mount being off a hair or two. Irregardless, a black border will absorb it and you won't notice it. I used black velvet. And my walls are a purple venetian plaster. Here's a pic with the camera flash:










As for behind the screen, I've been doing a number of reviews lately and other than the Carada screen material, most have some sort of black backing so that no light gets behind the screen. Or, as is the case with the HoloVega, it's thick enough so that light passing all the way through is minimal. Hope this helps!

mech


----------



## <^..^>Smokey Joe (Jun 29, 2007)

ahhh look, behind screen lighting....:daydream:


----------



## mechman (Feb 8, 2007)

Here's a couple more Smokester!

For those that say front projection doesn't perform well in lighted situations...










And one without the overheads:










mech


----------

