household paint and mediums - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 26 Old 12-30-08, 01:06 PM Thread Starter
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Re: household paint and mediums



thats slightly over color corrected.

the problem with trying to use high pigment paints means that even being accurate to ml can still cause variation.
this is one of the reasons we try to find a suitable base that does not need color correction.

we donot advise the the addiition of high chroma colors such as red,blue,green,yellow to diy mixes as it becomes very difficult to keep the mix neutral.
we'll do the hardwork so you dont have to
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post #22 of 26 Old 12-30-08, 05:56 PM
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Re: household paint and mediums

Quote:
mechman wrote: View Post
There's one here in this post.

mech
Thanks mech, I forgot that was there.

Here is a link to a page by Da-Lite that talks about retro-reflective and specular reflective screens that some might want to take a gander at: http://www.rentcom.com/wpapers/dalite/vol17.html

It's a bit "dry", but lots of info is there. One of things that was illuminating was the last statement, "These are the only things a projection screen can do: Reflect, Scatter, or Refract."
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post #23 of 26 Old 01-01-09, 01:36 PM Thread Starter
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Re: household paint and mediums

projector in the ceiling position!
a common setup for most home theaters

background:
projector just below ceiling
throw distance 14 feet?
no zoom appllied on lens of hd65
sitting position very slightly (1 foot) in front of projector
5:5:1 panel on left (n8.17), matt grey on right (n8.34)
camera set to black and white


room lighting only. matte grey is lighter as expected



100% white field with camera by projector - ie the ceiling position



100% white field camera at horizontal midline of panels



100% white field sitting/viewing position on axis



100% white field sitting in the worst seat of my setup (about 20 degrees from the middle of the two panels)



100% white field sitting position at about 30 degrees



100% white field sitting position at about 40 degrees



100% white field sitting positon about 45 degrees


100% white field at about 60 degrees. i had to move quite close to the panels as the side wall would not allow me to go further away.


100% white field at about 60 degrees from LHS


i only estimated the angles after the photos were taken so dont take them as exact.
i used a square piece of paper and folded it diagonally to give me 45 degress and again to give me 22.5 degrees. the paper was placed at the intersection of the two panels.
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post #24 of 26 Old 01-01-09, 02:33 PM Thread Starter
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Re: household paint and mediums

.
Quote:
Harpmaker wrote:
Quote:
custard wrote:
Quote:
Harpmaker wrote:
Quote:
wbassett wrote:
Quote:
custard wrote:
Quote:
wbassett wrote:

One question I have is it the medium that's causing the gain or is the medium making the mix more translucent and the aluminum causing the gain... or more than likely a combination of the two?
exactly!

i am in the process of making two white panels. one with medium and one without. hopefully that will enlighten us.
if the medium is not producing gain, then the panels should have similar angular reflective properties.
If we can get the mix more translucent not only will it be a bit lighter it will also allow more of the aluminum to do it's thing and make for a brighter image with darker shades of gray.



I haven't done any testing with it yet, but I got a bottle of Golden Fluid Titanium White and Fluid Matte Medium today; I can now compare testing with those to what Custy is doing.
Background:
i thought that the medium was causing paint to lighten. this was down to me seeing a lighter reading of my 5:5:1 panel when comparing to the equivalent panel without the medium.
i have doubts now wether this is the case.
especially now that i dont see the same effect with the white paint panels. the opposite effect is being seen but on a very small scale.
i havn't spectroed the white panels yet as the they have only been drying for 12hrs.

if you guys remember from the the previous posts - my sample reading for the 5:1 without the medium was reading lighter than when it was painted on a panel.





if we were to use the sample reading and then compare this to the panel with medium added (5:5:1) then you could say it was darkening the mix slightly



we could also hypthesize that below a certain Luminance value the medium causes lightening and above that value it causes darkening.
the white panel readings later today should help us reach a conclusion.

ok sorry about the babbling on!

methodology:

two panels primed with 3 layers of white paint.
1st panel painted with matt 2 coats of diluted (20%) white paint.
2nd panel painted with 3 coats of diluted (15-20%)medium:matt white 50:50

projector by ceiling, camera set to black and white

medium:matt white 50:50 on the left, matt white on the right.


room lighting - the medium panel looks slightly darker.


100% white field, camera by projector.


100% white field, camera at middle of panels


100% white field, camera in seating position


20 degrees off axis, seating position


30 degrees


40-45 degrees


60 degrees RHS


60 degrees LHS


conclusion:

the medium is adding a slight amount of angular reflectivity but not to the level that is being seen when aluminium is added.
note that the medium panel does not beat the straight white matte panel in the angular reflective position.
when aluminium was added we see it beats its counterpart in the angular reflective position.
also the aluminium panel was qiute a bit darker than than its counterpart as opposed to what we have with the white panels.

the only other factor to eliminate is wether something else in the lumitec is improving performance.
i will try and locate a suitable base in a standard matte finish.

if the lumitec is providing the performance boost then you guys should have no difficulty matching a base up in lumitec colors. here in the uk i dont think i can do that.
I concur Custy, well done.
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post #25 of 26 Old 01-02-09, 01:28 AM Thread Starter
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Re: household paint and mediums

the spectral readings after about 21 hours drying...






it seems that the matte medium is darkening the mix by a tad only. i wouldnt have thought it was anything to worry about.
the matte medium should cause the most change in hue with a light color and i dont see a big change.

i'll take another reading of them panels in a week and a month for changes.
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post #26 of 26 Old 01-08-09, 02:24 PM Thread Starter
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Re: household paint and mediums

it seems the golden fluid matte medium is not changing too much after a weeks curing.
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