HTS-X2 - an experimental N8 reflective screen mix - Page 8 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #71 of 92 Old 01-09-10, 02:35 PM
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pyro2
 
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Re: HTS-X2 - an experimental N8 reflective screen mix

harpmaker: I'm still a bit confused on the difference between your gain testing and umr's? You mentioned umr's results were slightly lower than what da-lite publishes.

umr's results for WA DW were actually slightly higher than mech's at 0 degrees but much lower at 18/20 degrees:
umr: 1.29 @ 0 degrees
umr: 1.04 @ 18 degrees Reference Link

mech: 1.26 @ 0 degrees
mech: 1.16 @ 20 degrees
Reference Link

The 0 degrees is only 0.03 which is probably within the range of test accuracy and/or product sample to sample deviation. However the 18/20 degrees differed quiet drastically. Any thoughts?

mechman: What panels do you paint your test samples on?

Just primed my main screen and a 54" x 36" sample that I'll send out to as many as possible. If everyone's testing could match within reason than that would be good. Perhaps evidence of this has already been proved before?

Any idea how much area I should get out of 54 fl oz of Elektra? I'm planning on two coats.
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post #72 of 92 Old 01-09-10, 06:48 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

Quote:
pyro2 wrote: View Post
harpmaker: I'm still a bit confused on the difference between your gain testing and umr's? You mentioned umr's results were slightly lower than what da-lite publishes.

umr's results for WA DW were actually slightly higher than mech's at 0 degrees but much lower at 18/20 degrees:
umr: 1.29 @ 0 degrees
umr: 1.04 @ 18 degrees Reference Link

mech: 1.26 @ 0 degrees
mech: 1.16 @ 20 degrees
Reference Link

The 0 degrees is only 0.03 which is probably within the range of test accuracy and/or product sample to sample deviation. However the 18/20 degrees differed quiet drastically. Any thoughts?
I want to be very clear that what I have said and what I am about to say are NOT meant to be a slam at umr in any way, shape or form. I believe his measurements are accurate under his test conditions and he has been very forthright in detailing his testing conditions. That said, those conditions are not what the projection screen industry use to determine the peak screen gain numbers they quote in their screen specifications.

From umr's last report posted here at HTS (bolding mine):
These measurements examined each screens reflectivity and color neutrality when viewed from the center and a seating position to the side in a dedicated home theater environment with a ceiling mounted projector mounted about 10 inches above the screen. The tests did not compare the mounting systems for the various materials tested.
and
The gains observed in this report are going to match a ceiling mounted projector system best. Screens with gain may perform better than that observed if the projector is mounted closer to the observers eye level.
and
The projector in this case was ceiling mounted in the center of the screen horizontally and vertically above the screen. Maximum vertical shift was used in this product. The projector was also warmed up for 2 hours before color measurements were taken to stabilize the output colors as much as possible. The spot measured was 32.5” lower than the projector’s center of projection.
and
Observations of movie images were made at 9’ at 18 degrees off center and sitting at the center of the screen with an 86” diagonal image and a maximum light level of 15 fL from the Classic Cinema White screen.

Umr's gain figures are what you can expect from the tested screens if your HT setup is similar to his, but they are not peak gain figures comparable to the gain figures produced by screen manufacturers. Mech's are. That is also how the DIY mixes were tested so there would be a level playing field and fair comparisons can be made.

To use the Da-Lite High Power as an example of a screen that will not perform it's best with a ceiling mounted PJ, umr's gain for this screen was 1.8. Da-Lite's published peak gain is 2.8. Mech's gain figure was 2.69. Not every screen coming off the production line will have the exact same gain, but it should be close. The reason for the discrepancy between umr and Mech's figures is that Mech measured peak gain and umr measured gain at the viewer's seated position in his HT. Both values are correct, but they used two different testing conditions.

As for the differences in the WA-DW measurements, I would say that the differing testing conditions may account for some of the difference, but also keep in mind that this "screen" is a laminate product meant for a whole different purpose and WA may have a wider tolerance in sheen level for a building product than a screen manufacturer would have. Meaning the two samples had two different sheens. Also, I have never before heard of any "shimmering" with DW.
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post #73 of 92 Old 01-20-10, 09:50 AM
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Re: HTS-X2 - an experimental N8 reflective screen mix

Two Elektra N8 samples 12"x36" have been sent out to mechman and harpmaker today.

The samples were painted on JoAnn's Black Out Cloth. One coat of Kilz primer was rolled on. Then two coats of Elektra N8 was rolled on using a 1/4" nap roller. The first coat dried for about 4 hours before the 2nd was applied. I painted on the textured side, not the smooth side. This was because the smooth side was a yellowish color, and I originally installed the fabric to project on the white side in case I left the BOC and never painted.

I painted a large piece of cloth and these two samples were right next to each other, so they should be identical. They are shipped in a baton looking roll. Unroll them asap so they don't permanently stay rolled up. You may have to re-roll them the other direction to straighten it out.

I look forward to your test results especially he Munshell gray level and spectro. I made the samples large enough so you can hopefully hang the sample and compare to other screens. I am very interested in your opinion with Elektra N8 vs BW and Scorpion. Pics are always nice, but I agree its sometimes difficult to tell.



I hope to have some screen shots soon - mainly for ohhs and ahhs.
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post #74 of 92 Old 01-22-10, 04:47 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

I received my sample today. I'm letting it warm up before I open and unroll it.
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post #75 of 92 Old 01-23-10, 11:39 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

I unrolled your sample today Pyro2, and it looks great! I doubt very much if you could have gotten a significantly smoother surface by spraying instead of rolling.

Here is my specto reading of your sample. It is very neutral (the a* and b* values) and where it should be in N level (the L* value).

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post #76 of 92 Old 01-23-10, 11:46 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

That's about as good as it gets! We want the 'a' and 'b' channels to be as close to the same value but opposite. That give the flattest spectral curve which is what we want.

"Make everything as simple as possible, but no simpler." - Albert Einstein

"If all else fails, spin the cat."- Grzboken
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post #77 of 92 Old 01-24-10, 09:00 AM
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Re: HTS-X2 - an experimental N8 reflective screen mix

Pyro2's numberes were:
L*a*b: 79.21 -0.44 0.53 RGB 196 196 195

Mine were:
L*a*b: 78.40 -0.44 0.39 RGB 193 194 193

A little different, but can one of you comment on whether the differences are significant from the perspective of the recipe as a good formula?

N7.8 vs N7.9 seems pretty small margin of error-wise. What of the other numbers?

Last edited by 1canuck2; 01-24-10 at 09:02 AM. Reason: fixed typo
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post #78 of 92 Old 01-24-10, 10:41 AM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

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1canuck2 wrote: View Post
Pyro2's numberes were:
L*a*b: 79.21 -0.44 0.53 RGB 196 196 195

Mine were:
L*a*b: 78.40 -0.44 0.39 RGB 193 194 193

A little different, but can one of you comment on whether the differences are significant from the perspective of the recipe as a good formula?

N7.8 vs N7.9 seems pretty small margin of error-wise. What of the other numbers?
I took both of these readings with my older DTP-22 spectrophotometer which has a wider swing between readings than Mech's later model i1 spectrophotometer, especially in the L* (lightness) value. Mech's readings are to be preferred over mine for absolute accuracy, but my readings are still definitely well within "the ballpark". Many hardware stores that offer computer color-matching for their line of house paints still use a spectro like mine for the job.

The largest difference between the two samples is in the L* value, but it is still only 0.81 and thus would be invisible to the eye even in side-by-side testing. Divide the L* value by 10 to get the Munsell N value. In this case that would be a difference of only N0.081. The differences in the b* value are getting close to the precision of my spectro and are also too small to be visible.

I'll quote from an article about the L*a*b* color space:
"The three letters in the CIELAB name refer to analogs of the three Hering opponent process dimensions: a* is the red-green contrast (a+ is a carmine red and a- is its opposite, blue green); b* is the yellow-blue contrast (b+ is light yellow and b- is deep blue). L* is the luminosity dimension, ranging from 0 (pure black) to 100 (reference white); values of L can go above 100 for specular highlights. These three dimensions create the L*a*b* color solid. Any spectrophotometrically measurable surface color can be located within the color solid as specific values for L, a and b, and the distance between any two similar colors approximately equals the apparent dissimilarity between them."

Just a note to anyone wanting more info on color spaces (like L*a*b* and sRGB), unless you really have a burning need to know these things researching this will melt your brain. Also, the a* value is sometimes called the red/green value and b* the yellow/blue value. The above quoted text was taken from a site that deals with water-colors.
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post #79 of 92 Old 01-24-10, 10:34 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

Thanks harpmaker! I'm very excited to see the measured results of the screen that I worked so hard on! I might just make that the background of my HTPC blu-ray player. nah, then I'll get too many questions from friends as to what the graph means and/or what is wrong with me! Great to see that 1canuk's results are extremely close as well. I'm confident we are both looking at the same screen : )

It's also about time I finally understood what the L a b values meant. Well now I at least understand the L, I'll have to give the a* and b* more time.

I'm still interested in your subjective evaluation of the sample especially in comparison to Black Widow (if you have it), since you have seen a large number of screens for reference. You might need some time to watch some new movies with the sample, but next time you do, drape that sample over a section of your screen.
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post #80 of 92 Old 01-25-10, 12:09 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

Quote:
pyro2 wrote: View Post
Thanks harpmaker! I'm very excited to see the measured results of the screen that I worked so hard on! I might just make that the background of my HTPC blu-ray player. nah, then I'll get too many questions from friends as to what the graph means and/or what is wrong with me!
Yeah, the minute you start talking about neutral grays and perceptual color spaces friends and family members start looking for the number to call the men in white coats!

Quote:
Great to see that 1canuk's results are extremely close as well. I'm confident we are both looking at the same screen : )
To the human eye they are.

Quote:
It's also about time I finally understood what the L a b values meant. Well now I at least understand the L, I'll have to give the a* and b* more time.
In a nutshell:
  • If a* is a positive number it is red, the higher the number the stronger a red is it.
  • If a* is a negative number it is green, the higher the number the stronger a green is it.
  • If b* is a positive number it is yellow, the higher the number the stronger a yellow is it.
  • If b* is a negative number it is blue, the higher the number the stronger a blue is it.

The final Hue (color) and Chroma (intensity) is the combination of the a* and b* values. The L* value describes how light or dark the color is (called Value in the Munsell color system).
http://en.wikipedia.org/wiki/Munsell

L*a*b* numbers are positional values in a 3-dimensional color space.

Quote:
I'm still interested in your subjective evaluation of the sample especially in comparison to Black Widow (if you have it), since you have seen a large number of screens for reference. You might need some time to watch some new movies with the sample, but next time you do, drape that sample over a section of your screen.
This testing will be done, but since this is still a hobby and we only have a limited amount of time to give to it I can't give you a time-line.
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