household paint and mediums - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 26 Old 12-16-08, 11:27 PM
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Re: household paint and mediums

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custard wrote: View Post
well harp i have some further interesting observations to report.

i dont think i am seeing the increase in reflectivity with my 8:1 AAA-M panel using the same testing parameters as above.
OK, please refresh my memory; did AAA-F at 4:1 work with this base?

Quote:
but i do think the 4:4:1, matte medium:base:AAA-M is showing the trait. only problem is that when viewing a 100% white field i can see some bright flecks from over 2 metres away.

i'll try and get some pics up at some point after further testing.
That is interesting! So it seems that when the base gets translucent enough for the aluminum to work, the "grain size" of the aluminum particles becomes a problem and specularity is seen.

Now the questions that come to mind are:

1. Would using less matte medium in the mix solve the specularity problem while still allowing the AAA-M to produce gain?

2. Would AAA-F work in the 4:4:1 mix? (We'll worry about color correction later)
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post #12 of 26 Old 12-17-08, 02:49 AM Thread Starter
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Re: household paint and mediums

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OK, please refresh my memory; did AAA-F at 4:1 work with this base?
i dont think i ever tested that but i'm pretty sure it will result in a severe blue push as the base is warm grey about n8.5


Quote:
That is interesting! So it seems that when the base gets translucent enough for the aluminum to work, the "grain size" of the aluminum particles becomes a problem and specularity is seen.

Now the questions that come to mind are:

1. Would using less matte medium in the mix solve the specularity problem while still allowing the AAA-M to produce gain?
ok, i know what you are getting at....
i'll have to order some more AAA-M. the amount i have left is not enough for another panel


Quote:
2. Would AAA-F work in the 4:4:1 mix? (We'll worry about color correction later)
that is something i can test although comparison with the AAA-M panels may not be ideal as they are lighter. but i can compare to my original UKBW wall.

looking at what mech has posted on the gain readings for BW it seems to imply that any gain is diffuse not specular.
my impression was that the above results were showing angular gain (specular)

it will be interesting to compare his BW readings to an equivalent matte N7.5 (veil)



completely off topic - we are using Bruce's RGB while Mech is using sRGB (Babel). i have noticed that the sRGB readings at D65 are slighty higher than Bruce RGB. maybe this is why your VUPE readings were slightly lower than mechs. the readings change more as we get lighter.
i do still think my Luminance readings are slightly lower than mechs but i can verify everything if we reach a point of needing to (i'll edit this paragraph out later as it is not relevant to this topic)
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post #13 of 26 Old 12-24-08, 05:34 AM Thread Starter
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Re: household paint and mediums

i received my charger for the laptop today so i was able to project some images. they show the increase in angular reflectivity with the panel that has the medium as part of the formula.

the panels:

LHS panel - 4:4:1 s1500n:medium:AAA-M, Lab 81.73 -0.27 0.46, RGB 202 202 201

Middle panel - slightly color corrected s1500n, Lab 83.41 -0.88 0.65, RGB 205 207 205

RHS panel - 8:1 s1500n:AAA-M, Lab 81.98 -0.28 0.70, RGB 203 203 201


photos taken in black and white with projector on a low table.

with ambient room lighting:



100% white field with camera near projector:



100% white field with camera in standing position:



also note that when the projector is placed in the ceiling position the increase in reflectivity is seen in the sitting position.
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post #14 of 26 Old 12-24-08, 09:23 AM
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Re: household paint and mediums

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completely off topic - we are using Bruce's RGB while Mech is using sRGB (Babel). i have noticed that the sRGB readings at D65 are slighty higher than Bruce RGB. maybe this is why your VUPE readings were slightly lower than mechs. the readings change more as we get lighter.
i do still think my Luminance readings are slightly lower than mechs but i can verify everything if we reach a point of needing to (i'll edit this paragraph out later as it is not relevant to this topic)
I thought I had responded to this, but if I did I can't find it. I've had a very nasty cold the last 10 days... can't seem to shake the sucker.

On Bruce's calculator spreadsheet, use cells L, M & N 41 to get sRGB values; don't use the Bruce RGB values in L, M & N 31. It's my understanding that RGB values are really not that much use since they are device-dependent.

Yeah, projector angle seems to be more important that I thought it would be. That makes sense though, it's the nature of reflection off any surface that is not a perfect diffuser (and very little is).
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post #15 of 26 Old 12-24-08, 12:51 PM Thread Starter
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Re: household paint and mediums

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I've had a very nasty cold the last 10 days... can't seem to shake the sucker.
lets hope the it does not ruin the festivities

Quote:
On Bruce's calculator spreadsheet, use cells L, M & N 41 to get sRGB values; don't use the Bruce RGB values in L, M & N 31. It's my understanding that RGB values are really not that much use since they are device-dependent.
gotcha!

Quote:
Yeah, projector angle seems to be more important that I thought it would be. That makes sense though, it's the nature of reflection off any surface that is not a perfect diffuser (and very little is).
so the 5:1 AAA-F panel, and the AAA-M panel with the medium is showing some signs of the gain we are striving to achieve.
i will have a go at altering the AAA-M/medium ratios in the new year in the hope of making the bright flecks disappear.

more to follow on the 5:1 AAA-F very soon aswell!

AND if anyone else has any ideas/thoughts that they want to discuss please don't hesitate - we don't bite.
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post #16 of 26 Old 12-24-08, 05:44 PM Thread Starter
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Re: household paint and mediums

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mechman wrote: View Post
Correct me if I'm wrong here but aren't we looking at retro-reflective gain? It's only seen sitting down, not standing up. How did you achieve that with paint custy? I can attest to seeing nothing sitting or standing in my AAA-M trials. But my pj is ceiling mounted, as harp said.

This is a clear matte medium you're using right custy?

Excuse me if this has all been hashed out already, it's my first time reading this! And we all know how poorly I do that most of the times!

mech
no worries mech,

definitely not retro-reflective otherwise the gain woul be seen when the photo is taken near the source of the light i.e near the projector.

to repeat: when projector is under ceiling the gain is seen when sitting down. when projector is located on the table the gain is seen standing up.

you also need to note that the optoma HD65 employs an offset.


my 8:1 AAA-M panel does not exhibit these properties - same as yours.

the 4:4:1 AAA-M panel with golden fluid matte medium (and the 5:1 AAA-F panel) do exhibit these properties.
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post #17 of 26 Old 12-27-08, 12:58 PM Thread Starter
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Re: household paint and mediums

i had a second attempt at mixing up the lumitec panel (5:1 AAA-F) discussed earlier in the thread.

the variance in readings between the sample and the panel occurred again

i made sure i primed the panel with three coats of white paint.
the mix i used was diluted about 25% and 4 coats were applied to the panel. the remainder of the paint was placed on a piece of card for the sample reading.

three different paints in the base mix - 4 lumitec, 1 crown base, 0.15 parts yellow



the sample reading



the panel reading


the drop in luminance from the sample to the panel and the increased blue push has baffled me.
do you guys think this may be caused by some sinking of aluminium in the sample?

i havent seen this much difference of readings between my other aluminium samples and their corresponding panels...
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post #18 of 26 Old 12-30-08, 10:07 AM Thread Starter
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Re: household paint and mediums

Quote:
Harpmaker wrote:
Quote:
custard wrote:
i carried out another small test today. i wanted to see what the fluid matte medium was offering to us in terms of translucency/reflectivity and gloss levels etc.

i used my 5:1 AAA-F mix and added some matte medium to it.
the mix was 5:5:1 base:medium:AAA-F.
the panel has been drying for 2 hrs only so i will leave further inspection until tomorrow

i have observed three things
1) the matte medium mix is lighter than the the equivalent mix minus the medium
2) increase in angular reflectivity is definitely seen.
3) i cant see much aluminium on the surface

so even though the aluminium ratio is down to 10% the angular reflectivity is still seen.
the increase in reflectivity should not be down to sheen because the matte medium is supposed to reduce it.
so my feeling is that the aluminium in the sub layers is maybe the special ingredient in this mix.
the only other factor could be the use of some lumitec in the base.

Your 5:5:1 base:medium:AAA-F mix come out to 9.09% AAA-F.

Don't judge anything until the sample has dried at least 6 hours, and I prefer to wait 24 hours before taking a spectro reading.

I think we all agree that the aluminum below the screen surface is active and making the mix more translucent will only increase the effect. I think we're on the right track increasing mix translucency. The LumiTec might be helping a little, but I think the beads it contains are so small that what you are seeing is due to a more translucent mix; but I could be wrong.
Quote:
wbassett wrote:
First things first though... let's see how the matte medium works at making things more translucent and what an image looks like on some test panels.
here are the preliminary test panel pics it has been drying/curing for about 14 hours.

on the left is the matte grey N8.34
in the middle is the medium:base:AAA-F 5:5:1 (will confirm reading later but is about N8.17 from uncured reading last night)
on the right is the medium:base:AAA-M 4:4:1 N8.17

black and white pics, projector on low table top. slight amounts of ambient light.

100% white field, camera by projector. retroreflective gain postion


100% white field, camera about middle of screen


100% white field, camera in standing position (equal to height of panels). angular gain position


black white bars standing position


zoom of grey scale. cant remember camera position
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post #19 of 26 Old 12-30-08, 10:27 AM Thread Starter
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Re: household paint and mediums

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custard wrote:
Quote:
wbassett wrote:
Well it's definitely angular reflective that's for sure.

To me what I see is in a normal projector configuration that 99% of owners use the center panel seems to look better. Is that everyone else's consensus?
yep, i'm of the same opinion.

i had placed that panel in the middle so that we could compare to two panels.

give me an hour or two and i will swap the panels around. from what i remenber last night movement of the panel to the side did not have too much of a detrimental effect.
i have rushed these images through so the quality may not be the best.

5:5:1 AAA-F on the left, matt grey middle, 4:4:1 AAA-M on the right.

room lighting


camera by projector


camera middle of panels


camera at height of top end of panels
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post #20 of 26 Old 12-30-08, 12:20 PM
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Re: household paint and mediums

It should be noted that the photos in the post above show how important it is to orient your projector to your screen type.

Screens that use glass beads (like the Da-Lite High Power) are retro-reflective; these types of screens will show the brightest image with the viewer (or camera) is at the same angle to the screen as the projector.

Screens that are specular (or angular) reflective (most DIY mixes) will show the brightest image when the viewer (or camera) is at the inverse angle to the screen as the projector, meaning that if you intend on viewing your screen setting down (like most of us ) you would want to mount the PJ on the ceiling.

I'll add some drawings to demonstrate these when time permits.
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