My Glidden Diamond 450 (White) Screen - Page 9 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #81 of 108 Old 01-21-13, 04:38 PM Thread Starter
Nak
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Re: My Glidden Diamond 450 (White) Screen

Quote:
mechman wrote: View Post
How did your measures end up?
Quote:
mechman wrote: View Post
Here are the readings:

Sprayed Sample

L*a*b* 96.5 -0.89 0.77
xyY 0.313 0.331 91.2
RGB 244 245 243

Rolled Sample

L*a*b* 96.9 -0.8 1.3
xyY 0.314 0.332 92.2
RGB 246 246 244
Here's what I measured:
Sprayed:
L*a*b*: 96.2, -.76, 1.48
xyY: .314, .332, 90.5
RGB: 244, 244, 241

Rolled:
L*a*b*: 97, -.82, 1.56
xyY: .314, .332, 92.4
RGB: 246, 247, 243

What I'm having a hard time understanding is that I measured projected light coming off the material nearly 10% brighter with the rolled sample, and yet they have the same on axis gain? I would have thought a straight reading would have been an indication of on axis gain, that the rolled sample would have higher on axis gain since it measured significantly brighter with my i1 Pro? I guess I don't understand enough yet, or maybe the paint cured further by the time you measured it? I'll take some measurements again tonight. I'll also put my panel of rolled 450 up against my screen and see if there's a visible difference.

Also, I need to send you my sample of Carada Brilliant White screen material. Supposedly, it's been measured at 1.2 gain--it's advertised at 1.4. I'm also at a loss to understand how measured light coming off the screen can favor the 450, and the Carada have a higher gain. I'll measure it again tonight, and then send it off to you if that's OK?

I'd like to understand all of this for curiosity's sake. Also for others reading this. I have to admit I'm still thrilled with my screen, and have no plans to re-paint any time in the foreseeable future. All my effort is going in to my Home theater/entertainment room re-model. Lot's of black velvet in the future.
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post #82 of 108 Old 01-21-13, 07:02 PM
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Don
 
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Re: My Glidden Diamond 450 (White) Screen

The i1 Pro spectrophotometer is a 45/0 ring illumination geometry device. This means that the sensor (actually a holographic diffraction grating with a 128 diode sensor array behind it) views the sample at 0 (on-axis) while the sample is illuminated at 45 by a "circle of light". This means that reflective readings can't be used to determine screen gain. While there may be a way to take emissive readings in a way that could correspond with proper gain determining methods, I don't know of it. The sensor/illumination geometry of the i1 Pro is designed to exclude the effects of sample specularity in reflective readings.

Screen gain measuring methodology is designed to specifically include sample specularity since that is what screen gain consists of. The sample under test is illuminated, then a 1 reflective spot meter is aimed at the center of the sample and then either the meter or the sample is tilted through the X and Y axises until the brightest reading is obtained. This is the on-axis gain of the sample. If off-axis measurements are to be made then the meter is rotated in an arc around the sample and readings are taken at various degree marks through the arc.
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post #83 of 108 Old 01-21-13, 07:27 PM Thread Starter
Nak
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Re: My Glidden Diamond 450 (White) Screen

I understand that... I understand that to actually measure gain a spot meter is required. I guess I don't understand how one material can be measure brighter, but have a lower on-axis gain? I realize the i1 Pro can basically ignore specularity in reflective readings, but we are talking emissive (sp?) readings. Yes, the screen is reflecting PJ light, but the Pro doesn't know that. Reflective readings with the Pro are taken with it's internal light.

Obviously to get a real idea of total gain, you need off axis readings. However, it still seems to me that on-axis gain should be somewhat indicated by comparison. I freely admit I do not understand this anywhere near completely, and could easily be missing something. But if I measure PJ light coming off a screen, and stick a different material on the screen in front of the meter, shouldn't the readings be an indication of the relative on-axis gain of the two materials?
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post #84 of 108 Old 01-21-13, 07:50 PM
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Re: My Glidden Diamond 450 (White) Screen

Quote:
Nak wrote: View Post
I understand that... I understand that to actually measure gain a spot meter is required. I guess I don't understand how one material can be measure brighter, but have a lower on-axis gain? I realize the i1 Pro can basically ignore specularity in reflective readings, but we are talking emissive (sp?) readings. Yes, the screen is reflecting PJ light, but the Pro doesn't know that. Reflective readings with the Pro are taken with it's internal light.

Obviously to get a real idea of total gain, you need off axis readings. However, it still seems to me that on-axis gain should be somewhat indicated by comparison. I freely admit I do not understand this anywhere near completely, and could easily be missing something. But if I measure PJ light coming off a screen, and stick a different material on the screen in front of the meter, shouldn't the readings be an indication of the relative on-axis gain of the two materials?
Are you using the i1 diffusion dome when you take the emissive readings? The dome will basically "even out" the light hitting it which is the opposite of what you want to do taking a gain reading. A lot would also depend on how far your i1 is away from the screen; the further away it is the more of the screen it will "see". I would think that the flatter the paint finish was the more accurate this method would be, but I haven't seen a paint that was truly devoid of gloss yet.

It could be interesting to take some readings without the dome (if you are using it).
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post #85 of 108 Old 01-21-13, 08:09 PM Thread Starter
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Re: My Glidden Diamond 450 (White) Screen

Nope, I only use the dome to take readings directly off of the PJ.
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post #86 of 108 Old 01-21-13, 08:13 PM
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Re: My Glidden Diamond 450 (White) Screen

Quote:
Nak wrote: View Post
I realize the i1 Pro can basically ignore specularity in reflective readings, but we are talking emissive (sp?) readings. Yes, the screen is reflecting PJ light, but the Pro doesn't know that. Reflective readings with the Pro are taken with it's internal light.
Probably i miss something here...i was quite sure that i1 uses it's internal light only for emissive readings and not on reflective ones. Are you sure Nak? I 'm asking this because every time i get some readings from the screen the internal light does not seem to be working at all...
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post #87 of 108 Old 01-21-13, 09:09 PM Thread Starter
Nak
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Re: My Glidden Diamond 450 (White) Screen

That's correct. When you take a reading of of the screen, the meter is in emissive mode and no light comes on. The source that it's measuring is emissive. When you take a reflective reading--as in putting the meter directly against some material like paper or something--the internal light comes on so that it's internal light hits the material and is reflected back at the meter.
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post #88 of 108 Old 01-22-13, 02:53 AM
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Re: My Glidden Diamond 450 (White) Screen

Quote:
Nak wrote: View Post
That's correct. When you take a reading of of the screen, the meter is in emissive mode and no light comes on. The source that it's measuring is emissive. When you take a reflective reading--as in putting the meter directly against some material like paper or something--the internal light comes on so that it's internal light hits the material and is reflected back at the meter.
Ok!! Thanks a lot!!

I probably mixed up things by thinking the projected light that's being reflected by the screen..
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post #89 of 108 Old 01-22-13, 11:42 AM Thread Starter
Nak
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Re: My Glidden Diamond 450 (White) Screen

Thanks Mech!

I believe your numbers, I just don't understand mine. (Not color balance, but measured light.) Could be just final curing. I didn't get around to doing measurements last night, I'll try and get to it tonight.
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post #90 of 108 Old 01-22-13, 07:34 PM
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Re: My Glidden Diamond 450 (White) Screen

Quote:
Nak wrote: View Post
Nope, I only use the dome to take readings directly off of the PJ.
I'm going to have to start writing down what equipment folks have on this forum since my mind (or at least the memory portion) seems to have "left the building".

What CMS software are you using? I was under the impression that all CMS software used the i1 diffuser dome for measuring either PJ or screen. I would love to find a CMS that didn't require the diffuser since my i1 doesn't have one and X-Rite says it's firmware can't be updated to use one (which makes no sense to me whatsoever).
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