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post #41 of 67 Old 09-30-07, 09:55 PM Thread Starter
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Re: The Problem with Iridescence cont.

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cynical2 wrote: View Post
Freudian slip?

Nah, but I do see a major difference. Opaque and translucent materials will behave differently and have a different interaction with light. Nothing I am saying or making up, that's a fact and part of the physics of light and objects and how they interact.

I want to be clear on something, I acknowledge that commercial companies use mica based pearlescents to boost brightness and gain. I am saying we can't just dump things in and expect the same results as commercial screens. I also agree that just because something has pearl (mica) as part of the mix it shouldn't be discarded solely because of that... and no I'm not saying mixes should be discarded either.

We already know that yes, acceptable does work, but again I ask is DIY only shooting for 'acceptable' or are the developers shooting for the best? I consider myself a developer and I am striving for not only the best, but also to make things easy. I know some of these explanations seem complicated to many, but that's the behind the scenes testing and research that goes into easy. If it was as simple as going to the store and selecting a gray from a color swatch that looks 'good', then we'd have been done years ago. Acceptable and 'best', or optimal, are two different things to me. We have both and yes there is a viewable difference between them. To some it may not be enough to bother with, but again I ask if something is as easy as walking in and saying you want a certain color, how can that be considered hard or 'elitist'? It's not. It's a matter of information and education. The only way to show the difference is with testing and hard data. Well... yes our eyes can see it if given the comparison, but convincing people there is a difference and to actually do the comparison is the hard part. If they don't know or haven't compared things, it's hard to tell someone that one thing is better than another. That's why I like to have data to back things up.

The same goes with optic coatings. Yes there are present methods that will work and are acceptable, but there are also some other methods that are just as easy to obtain but yield even better results. So why stop at acceptable? The goal should be a method that increases detail, clarity, and color reproduction without altering the image. I do think we can do that. I don't think we can do that without some thought though.

What I would like to see are some tests done before and after the pearls are added to various mixes and top coatings to try and track any changes introduced and how much of a change and in what direction. That will be valuable information to have.

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

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post #42 of 67 Old 10-01-07, 10:13 AM
 
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Red face

I agree with all of Bill's points in the previous post. As time goes on there will be better solutions dialed in properly with careful testing and backed up with measured color data. You can't just throw some pearl in polyurethane and expect to get the correct color balance or gain curves. There is a science to all this and my work was mostly trial and error and at that time the color data was suspect.

In the mean time the neutral gray proprietary tints like Gray Screen and Winter Mountain are excellent painted screen solutions and when those are not available the EasyFlex tints will yield reasonably good results for most modern projectors. As we know most of these new projectors can produce a nice image on a brown paper bag.

In short order I suspect the EasyFlex solutions will be rendered obsolete and that is a good thing. That means progress has been made and better solutions have been developed. DIY Screen technology has made a huge leap in the past few months and I am way out of my league now. The solutions that will be developed and identified by Bill and mechman in the next few months will leave EasyFlex in the dust. Those screen shots of the liquid aluminum screen Bill is working on demonstrates that clearly.

P.S My original posting was not very well worded and did not properly represent my thoughts on this subject.

Last edited by Tiddler; 10-01-07 at 03:21 PM.
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post #43 of 67 Old 10-01-07, 03:25 PM Thread Starter
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Re: More Than Acceptable!

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I agree with all of Bill's points in the previous post. As time goes on there will be better solutions dialed in properly with careful testing and backed up with measured color data.

In the mean time the neutral gray proprietary tints like Gray Screen and Winter Mountain are good beginner painted screen solutions and when those are not available the EasyFlex tints will yield reasonably good results for most modern projectors.

In short order I suspect the EasyFlex solutions will be rendered obsolete and that is a good thing. That means progress has been made and better solutions have been developed.
Honestly this isn't about rendering something obsolete, not to me at least. If we have something easily available, then why not use it?

You mentioned in the post before editing it that you tried to go with items easily obtained by anyone in the US, and that is an excellent mindset. I think though that you may have overlooked that we seem to have access to a wider variety of Home Repair centers that don't seem to be available to you. So what's easily obtainable for us seems difficult for you, and vice versa... you can easily obtain the pearlizing medium but many in the States can't seem to find it locally. Do-Able is another example. For those that can get it, it's incredibly easy and an outstanding screen. For those that can't, it really doesn't matter how good it is if they have no way to get it. In this case, at least people can order the pearlizing medium if they want it.

For those that only have a Home Depot available, your method is excellent. I recently ran into a site that someone created about how they did not have a Home Depot but did have a Sherwin Williams close by. Silver Screen was the rage, so they set about having a Sherwin Williams color match done. To me that makes very little sense. They could have went with a much better solution and in this case it would actually have been easier for them to get. To be fair, at the time that's all they may have known about.

As far as the expense, that may not be an issue at all. Gray Screen and Soothing White are not Duration exclusive. There is no reason why it can't be mixed using Luminous White as the base, but... I would personally want to get some first and spectro it to make sure of the balance. So to stay in line with my previous post, I am sure it would be 'acceptable' I wouldn't call it anything other than that until some readings were done.

Lowes can make anything from any company/brand. Still, I want to test those too. So I'm being equally as tough on the neutral grays as I may seem to be on everything else.

Easy is still easy to the end user. The behind the scenes testing to identify things is what's hard, but again, the end users don't have to worry about that.

As far as trying to improve things and make them better- Fashion Grey may actually be stepping down because we may have identified a better color balance. If that's the case, I call that progress. It still stays the same as far as ease of installation for a simple substrate one step method though; so nothing will change for someone wanting to use that particular method aside from a better recommendation is now being made. In the end, it is still just as easy. I really do try to adhere to KISS.

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

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post #44 of 67 Old 10-03-07, 02:42 PM Thread Starter
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Re: Gain and other confusing topics.

This will be the last entry on the iridescence/mica topic unless anyone has any other comments or questions.

The main point I am making is a bit of caution is all. Also for people to keep in mind that craft paints are pretty low on the quality list of things and their tolerances and Quality Assurances aren't going to be as tight as other industries. If we think about it some, is a company going to spend a lot of money on tolerances on things that sell retail for a buck? Again, not slamming anyone, I am just saying we can only go so far with certain items.

I spoke to Da-Lite about this topic since they do indeed use mica in some of their screens. This is what they said:
Quote:
Alex at Da-Lite wrote:
I received the following reply from one of our chemists regarding our conversation, "You can rest assured the pearlescent we use shift the least amount of anything available. The primary factors effecting the shift (particle size, angle of light reflection, thickness of the interference coating on the pearlescent material, etc.) are all very carefully chosen, engineered and controlled by Da-Lite to produce the least amount of color shift possible for the desired optical effects designed into each screen surface."
("least amount of color shift possible"- meaning they also acknowledge even with proper control there is a color shift of some extent.)

So again, unless there are anymore comments or questions, I think it's safe to say yes it works but have some caution as to how much is used. The commercial companies confirmed exactly what I was saying previously and that is they adhere to very tight specifications that I seriously doubt we are going to get from the craft industry.

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post #45 of 67 Old 10-08-07, 08:26 PM Thread Starter
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What Constitutes a Neutral Value?

Isn’t Color Color?

All televisions and projectors use the primary colors of red, green, and blue to create all of the colors in a video signal.

Some may be thinking right now “But I was told in grade school that the primary colors are yellow, red, and blue.” They are, but for paints and inks. They are two different color systems, one is additive (such as our projectors and TVs) and the other is subtractive, as mentioned paints for an example.

With paints what we see from the painted object is after the paint absorbs all the light other than the color it reflects back to our eyes. With additive colors, a specific wavelength or wavelengths are being created. The easiest way to think of this is with additive color (like our projectors), light is being created directly; with subtractive color, light is absorbed and reflected. We deal with additive colors with our projectors, and subtractive colors with our screens.

Because of the way the eye works, red, green, and blue are the colors projectors and TVs add together to create other colors. So in the additive system red and blue mix together for magenta- red and green mix together for yellow. By varying the amount and intensity of each color a display device can create different shades.

Color Spaces

So what is red and why? What looks red to one person may look reddish-orange to someone else. Color is in our heads and we are taught what they are. Because of this there needs to be a standard, otherwise every TV show, movie, printed media would all have different look and color depending on who was supervising the material, and in reality the broadcast system wouldn’t work. You certainly would not be able to adjust your set or projector because the very next channel or DVD you put in would not necessarily match the previous adjustments. Think about that for a moment and a world where every time you changed the channel you had to go through a color adjustment all over again. There wouldn’t be any calibration standards because it would again vary from person to person and company to company. See now how this would be a mess and why it was stated that without a set of standards things wouldn’t work?

In 1990 the Rec .709 (Recommendation ITU-R BT.709) which defined the exact red, green and blue points for broadcast and the HDTV standard. These point may look familiar to a few that have read some of the other threads throughout this forum… they are the ‘x’ and ‘y’ coordinates found on a CIE chromaticity diagram. The chromaticity diagram is a visual and numerical representation of color. Use it and you’ll never have to ask which way a color leans, you will be able to see it right away. In this sense the Yxy, or primarily the ‘x’ and ‘y’ values are better than sRGB numbers to determine the actual color shift we are looking at. RGB is a snapshot but the CIE diagram gives us a more complete picture.


With this specification in place content creators will know that their cameras will output a certain color, they can edit and correct those colors to a specific reference point, and the end result that we see is on our screen what was actually seen without any camera shift or biasing.

Without this specification and reference even within the CIE chromaticity diagram, people could pick their own ‘reference’ and we’d be back to having things all over the place. The movie and television industry settled on D65 as the neutral reference point and everything is keyed to that point. If every step in the chain follows this standard and reference point then what you see will be what the director intended. Sometimes directors do use different film stock and color techniques for a ‘unique’ look, some examples would be Sin City or 300, Charlies Angles to name a few... but they still reference the industry standard to ensure their ‘look’ will remain the same no matter where it is displayed.

That is why D65 is mentioned so much throughout this forum and why I use it as a reference point and target as well as what the industry shoots for. Certainly you can adjust your projector to a value that isn’t D65, but it will not display things they way they were intended to be seen nor will it be optimal.

So how can you tell if a neutral is 'neutral'?

I have seen some questions asking how one color can be said is neutral and another is not. First we have to state that there is a tolerance that determines if something is neutral and that is +/- .5 from zero based on the CIE L*ab readings, specifically the ‘a’ and ‘b’ values.

A CIE L*ab value of say 81 0 0 as referenced to D65 would be dead on neutral. If we had Yxy readings the same color would be 58.471096 .312712 .039008, which is the same, dead center neutral for D65, and that comes out to an sRGB value of 201 201 201.

That's some pretty tight specs and it means if we went with that then only that would be considered neutral, but there actually is a tolerance. That tolerance is +/- .5 from zero based on the L*ab readings. So these would be acceptable neutral readings: 81 .5 .5, 81 .5 0, 81 0 .5, 81 -.5 .5, 81 .5 -.5, 81 -.5 0, and 81 0 -.5 and everything in between the 0 to +/- .5 value. Still pretty tight but well within our neutral standard and goal.

I will say it again, there are many colors that we can use that will provide an acceptable image, but I was striving for optimal, or the 'best' when I decided to start researching neutral grays. Many have said it was the goal but too hard to achieve. We just weren't looking in the right areas or more important, at the numbers.

(Note: There are two values for Silver Screen listed, one is what Behr came up with, and the other is an independent source. We'll have new readings soon and compare everything and post the most consistent values.)


Of course the red dot in the center is D65. The next ring is the +/- .5 range. The next ring out was expanded to +/- 1 which is a near neutral, and the last ring is at +/- 2 which is starting to get into a caution zone. Depending on where a color is in the caution zone could be the difference between being able to calibrate with no apparent color shift or issue or having some problems with color shifting. We also have to take into consideration the projector and our eyes too. Some people may be able to see a color shift better than others.

One thing to mention about the chart is it uses the xy coordinates to plot color value, and I just expressed tolerances for L*ab notation. That’s fine because since we have standards we can convert back and forth between these color spaces and know we are talking about the same colors. There is a lot of math and science involved but I felt getting into math and equations was more than most want to read about.

Out side these tolerances, especially from +/-1 out are colors and not true neutrals or near neutrals. We do know there are colors outside the target that will work and provide a very nice image, but the closer we get to D65 the more accurate the color reproduction will be. To some this may be minute or they may not even see much of a difference, to others, they will see a big difference. As mentioned previously that has to do with the fact that our eyes are all different and we see colors different from one person to the next. That is also a reason why a color standard was developed.

So we can now 'see' where these colors fall in respect to our neutral reference point of D65, and depending on who's measurements you go with, Behr Silver Screen is a near neutral with one and in the caution zone with the other reading.

For lighter shades, we know they don't push as hard so the color shift isn't as harsh. The darker the color shade goes though, there will be shifting the further away from our neutral reference point that the color is.

[MOUSE]Note: A true neutral is not actually a color.[/MOUSE]

For one of the best explanations of color spaces and neutral reference points check out the Whibal video here. I could go on and on about this citing from text books to various websites because there is much more involved than this brief overview, but Michael Tapes gives the easiest explanation I have seen, and it's kinda fun to watch too. Then again I could be a bit weird!

Also check out the next video that talks about color spaces and spectral curves, very good videos. For fun if you are still interested, check out why we need instruments when getting this precise and see how your eyes can lie to you.

A color is a hue and they absorb and reflect light differently than a neutral. A green color will absorb all of the light spectrum except for green which is reflected back and why we see it as green. A blue-gray or green-gray will reflect back a stronger blue or green reflected light which is why we see it as a blue or greenish gray color (Remember, neutral is not a color). This is where we get our color shifting from. Can we use non-neutrals? Absolutely and many are using them. It still doesn't deny the fact that the closer we pull things in towards our D65 neutral reference the better and more accurate the projectors colors will be as reproduced by the screen.

Hopefully this explained a little on color theory, why we have standards, and what constitutes a neutral value.

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

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post #46 of 67 Old 10-14-07, 12:23 PM
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Re: Gain and other confusing topics.

Let's revisit iridescence for a moment...

Your previous comments on color shifting and refraction of light are accurate, but they are all based on one premise: full spectrum white light. But this sort of light (except for ambient sources) is not present in a projection situation - the projector sends three colors, and all three are reasonably monochromatic. You can't change red, green, or blue into any other colors by refraction - or can you?

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post #47 of 67 Old 10-14-07, 12:54 PM Thread Starter
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Re: Gain and other confusing topics.

I think we do all agree our projectors send three colors, red, green, and blue, and if only red green or blue were being projected we would have a pure color of one wavelength that is monochromatic, but rarely is just one color or wavelength being projected.

Plus we still have the issues of light going from one medium to another and when it passes though the denser mica platelets it gets bent and refracts. Even if the incoming light is of a pure nature and of a singular wavelength, it will still slow down and be 'bent' upon entering and exiting the denser mediums. If it is out of phase then it subtracts from our image, if it is in phase it will add or 're-enforce' the image. I don't think we are at any known level where we can actually engineer things to guarentee everything is in phase and additive.

Like I said before, we do know we can brighten things up some, all I was saying was for some caution to be used. You know how it can go, if one of something is good, two must be better, and before long four is said to be incredible and so on, and mica being an iridescent can have an affect on the image. Even if that affect is slight, would it not be better to look for something that doesn't have this as one of its characteristics? I think non-interference pigments and materials are a very interesting and virtually overlooked alternative.

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post #48 of 67 Old 10-15-07, 12:00 PM
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Re: Gain and other confusing topics.

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mechman wrote: View Post
Dr. Burrows has a PhD in all of this and consults with Da-Lite as well as other screen manufacturers and he does feel mica, aka iridescents can have a very negative affect on a projected image and if 'monochromatic' light was a non-issue he would have taken that into consideration.
To me, brainstorming new ideas is the essence of DIY. Personally, I think we're capable of exceeding commercial screens, not just duplicating them. Sure, mica can cause problems - but so can virtually any ingredient. Besides, if I wanted the best Dr. Burrows has to offer, I'd just buy a Dalite.

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post #49 of 67 Old 10-15-07, 03:42 PM
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Re: Gain and other confusing topics.

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To me, brainstorming new ideas is the essence of DIY. Personally, I think we're capable of exceeding commercial screens, not just duplicating them. Sure, mica can cause problems - but so can virtually any ingredient. Besides, if I wanted the best Dr. Burrows has to offer, I'd just buy a Dalite.

Garry
Are you implying that you understand screen technology and the physics of colors (and light projection) better than a PhD that does this for a living? We're not talking about "other ingredients"...we're discussing mica. Burrows, with his experience/knowledge, clearly states that iridescence negatively impacts the image. Additionally, mech posted an image that demonstrates Burrows' conclusion. So, while the use of mica is widespread (I have it in the topcoat on my own screen), it seems pretty clear that it's use moving forward should be minimized to avoid image degradation.

It seems unbelievably optimistic to seriously believe that people at home, in their garages and basements, are going to "exceed" the R&D efforts at the major companies developing commercial screens. Together, these companies spend millions (tens of millions) of R&D dollars understanding and improving the technology. They do so in world-class laboratories using elaborate measurement devices...some of which cost more than the typical DIY'ers family car. They have a bevy of scientists that understand the science far better than the best the DIY community of hobbyists has to offer.

In short, it's not even a fair fight. You'd really have to believe that the scientists at these companies are idiots...that the intellect of the DIY community is so superior to that of the screen company scientists that it could make up for the huge deficit in lab facilities, measurement equipment, knowledge of the physics, and experience gained from developing screens full-time.

The DIY community can match/exceed simple commercial screen solutions, but simply doesn't have the mechanism to deliver alternatives to the more complex of commercial screens. Take a look under a microscope at the uniform laydown of glass beads in the HP screen for evidence...or the uniform textures created by fabric processing of commercial screens. The DIY'er simply can only play in one area...the screen companies can play anywhere that the physics takes them...they have the technology to enable just that.
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post #50 of 67 Old 10-15-07, 04:31 PM
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Re: Gain and other confusing topics.

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cynical2 wrote:
Are you implying that you understand screen technology and the physics of colors (and light projection) better than a PhD that does this for a living? We're not talking about "other ingredients"...we're discussing mica. Burrows, with his experience/knowledge, clearly states that iridescence negatively impacts the image. Additionally, mech posted an image that demonstrates Burrows' conclusion. So, while the use of mica is widespread (I have it in the topcoat on my own screen), it seems pretty clear that it's use moving forward should be minimized to avoid image degradation.
No, at no point did I state that I understand anything better than a PhD, but neither do I believe that all innovations must come from a white coat with a million dollar budget. If Burrows and others are the "source of all knowledge", then why bother with a forum? So we can discuss their wisdom? Sorry, but I will continue to believe that us common folk are capable of independent thought, experimentation, and useful invention. If the goal is to copy commercial screens - while admitting our inability to do so - I guess I've opened my mouth in the wrong arena. My apologies.

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