HTS-X2 - an experimental N8 reflective screen mix

1canuck2 said:

Slightly OT: Generally speaking, total neutrality is the ideal goal, but also exceedingly difficult to get perfect. So how big a deal is it? Is not the purpose of a calibration to correct for such differences? I understand a big push in one colour may be too big to correct for, but little ones should be no big deal. Could you actually have a screen surface that is a better overall performer in other respects but exhibits push in one colour. A good calibration can correct for the push, leaving you with a better screen than one that was perfectly neutral but less well performing in other respects?

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I'll leave the calibration and colorimetry stuff to Mech and Bill, but I'll weigh in on this. A perfectly color neutral screen is very hard to get, as is a perfect anything in the real world; but luckily we don't need true perfection. Some time ago Bill and Dr. Mark D. Fairchild discussed the matter and came up with a set of neutrality standards for projection screens (which is what we currently use to determine levels of screen neutrality). Most projectors can compensate for small screen neutrality variances, but the more a PJ has to compensate the less chance it can do so properly and the greater chance it will throw other colors off at the same time; thus the desirability for as neutral a screen as possible. Also, the further a screen is from neutral the greater image colors will vary as the projected image drifts away from D65 (an effect called metamerism). Very few screens are perfectly neutral, very few PJ's are perfectly D65 - thus the need for calibration.

Yes, if you need a screen of a certain brightness and that brightness could not be attained with a neutral screen you would have no choice but to use a screen that would achieve that brightness even if it were less neutral. The thing is, screen neutrality (at least with a painted screen) isn't all that hard to achieve if it is approached from a scientific aspect.

The case above where someone hypothetically had to settle for using a non-neutral screen to achieve a viewable image is a case where the wrong projector was being used. Bill has said for quite some time that home theaters should be designed by determining what lighting conditions the screen will be viewed in (no ambient light or lots of it) and then go shopping for a PJ and screen. This makes so much sense! Unfortunately, most people either get whatever PJ is on sale, or buy one that a friend says works well, without taking their viewing conditions into consideration. That leaves them trying to find a screen that will compensate for using the wrong PJ. Many times this can be done, but has definite limitations. No screen can totally compensate for not having enough lumens to start with.

I understand as screen formula developers that the holy grail is totally neutral, but is there a risk that goal is followed to the detriment of other goals? For example, on other forums it seems that gain or reflectivity is the goal, to the detriment of neutrality. I'm not claiming to understand the complexities of the art/science, just curious...

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I would say the simple answer is no. Neutrality doesn't affect gain. The color of a screen has nothing to do with it's reflective properties other than how much light it absorbs rather than reflects. The darker the screen, the less light it reflects.

Screen gain is a subject that is almost universally misunderstood. There is a general feeling that more gain is better no matter what. This is just the opposite of what it true. Think of screen gain as the ability of the screen to focus the reflected light toward the central viewer. To do this it needs to redirect light away from somewhere else to point it straight toward the audience. This means that those light rays are not being reflected to areas distant from the central area on-axis with the PJ. This makes for a darker image for those side seats. No screen generates light, it can only reflect what light it receives from the PJ. If a screen has too much gain it will also hotspot, which is when portions of the screen are visibly brighter than other areas of the screen which should be the same brightness.

We only need gain when the projector isn't bright enough for the job. In the past this had been the case more often than not, thus the need for screens with as high a gain as practical. With todays PJ's approaching the 10,000 lumen mark I personally think that the days of high gain screens are just about done.

The other mixes you are probably referring to were designed with gain as the primary goal and neutrality was deemed not to be all that important (and still doesn't seem to be). Back in the day they were designed PJ's had way fewer lumens than they do today.

The perfect screen is one that can't exist in reality. It would be totally black so it would absorb all ambient light hitting it yet it would still reflect 100% of the projected image to a wide audience.

1canuck2 said:

Harp, I tried PMing you but your box is full...
Did you get the sample painted card I mailed you?

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Sorry about that, I have an embarrassing tendency to let my inbox get full. :blush:

Yes, I got your sample and it looks great! Below is the Spectral Reflectance Chart for it. The bump in the deep violet and orange, and the dip in the extreme red end of the spectrum are indicative of a very neutral mix. We still don't know why neutrals have this curve. :dontknow:

The L* value equates to a N value of 7.84, which is a tad under the 8.0 value of a true N8, but only the most discerning eye could tell the difference even in side-by-side testing. The a* and b* values are both well under 1.0 and the fact that they are opposites (one negative and the other positive) is also very good.

The color temperature of this mix is 6487°K which is only 16° off from the D65 standard of 6503°K.

Well done! :clap:

1canuck2 said:

The colour temp is only ~0.25% off, I'd say that's a pretty small margin considering how simple the formula is (three ingredients). So if the goal is simplicity with consistent results, that's very impressive!

The N value as well is a pretty small margin (2%), so all things considered an impressive result (and a lower N is probably okay for me anyway since I have good light control and a powerful PJ lumens-wise).

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I believe I mentioned this before, but the reason we design to such exacting neutrality tolerances is to allow for some error either from the user or the paint store. It isn't uncommon to have some variation due to mistinting when using tinted house paints, although this seems to be getting less as tinting systems improve their consistency.

We also try to make our mixes as easy to assemble as possible with little, or no, actual paint measurement; just pour the paints required into a bucket and stir. This lesson was learned from building the mixes posted on another forum where some ingredients had to be measured down to the milliliter or less. Many people have problems doing this, especially with some of the thicker artist paints used to color mixes. Such colors are concentrated and even a small error will make a difference in the final color of the screen.

In the mix family that HTS-X2 will be a part of the range of gray shades will be determined by how much neutral gray paint is added to regular C&S. In theory this would be an "infinitely adjustable" mix with any value from C&S alone (N9) down to where the gray paint comprises too much of the mix and the reflective properties of C&S are visibly diminished. In the real world this infinite adjustability is more about marketing hype than truly useful. Through testing and observation we have determined that there isn't much sense in having mixes closer together than N0.5 which is a "half-N" step.

Not sure if I told you, but the sample card was rolled at the same time as the screen. I did coat 1 on the screen, then rolled the card. Waited. Then coat 2 on the screen, rolled the card. Waited. Then coat 3 and rolled the card. So its pretty representative of what went up on my wall. The only diff is the card was not primed with Kilz2, but it was a white card from a frozen food box. Given I put three coats on, I'd guess the primer (or lack thereof) would make a minimal difference.

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I forgot to comment on this before, but if your screen surface is the same as the sample card you would have gained little, or nothing, by spraying instead of rolling! That sample is the smoothest rolled sample I have ever seen. :T

As I've said before, I am exceedingly happy with the results, but its nice to have some science to back-up my satisfaction.

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Yeah, I have no idea why some people are against scientific measurement of DIY screen mixes, unless perhaps the results would disprove their comments on screen performance - but I won't go there. :devil:

1canuck2 said:

Well I certainly think the idea is a great one. It was very easy to mix - the addition of the N6 to darken an already tried and tested formula is a bit of a stroke of genius if you ask me.

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Thank you. The concept is based on Scorpion™ being two neutral screen mixes added together. A neutral plus a neutral equals a neutral. My experience with CSMS is that as the mix gets darker the reflective flakes become more apparent so the concentration should be lessened, thus the N6 paint does two jobs, it darkens the mix and it dilutes the CSMS so the mix isn't too reflective for the shade.

Theoretical question: how would BW compare to C&S plus enough N6 to be as dark as BW? Could it be better, or is it expected to be worse?

Next theoretical question: could a "lightener" be added to BW to achieve similar results?

Last question: Would this formula replace Scorpion? Its certainly easier to make (which is why I got here), it seems neutral enough, but is Scorpion "better"?

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These are excellent questions and more comparative testing will need to be done to truly answer the first one. I would expect that C&S™ darkened to the shade of BW™ would offer similar performance characteristics, but only testing will determine that. At the N7.5 shade the darkened C&S™ would have a bit higher concentration of reflective flakes in it, but the aluminum in BW™ is probably the better reflector.

As for lightening BW™, it was found that white paint could be added to lighten the mix to N8 without affecting the reflective properties too much, but that was the limit. I believe the ratio for that mix is 4:1:1 Bermuda Beige/AAA-F/White.

I like the idea of the Scorpion™ mix since it is based on two proven mixes simply added together. Again, testing has to be done to determine if HTS-X2 performs as well as Scorpion™, but my gut feeling is that it won't. However; that is why we test - to actually know and not just guess.

Well thank you The only trick I can share is that I am pretty . I have done a fair amount of rolling for house decorating, so I have a bit of experience, but this was still a slightly new challenge, but probably only because I was more obsessive about it.

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I have to assume that there is a word missing after "pretty", my guess is that for some reason it didn't make it through the "naughty filter" used here at HTS. Either that or brushing your teeth and combing your hair really does help roll a smooth screen. :rofl:

Hoping to do a second round of calibration today, but then I just bought an Xbox 360 for the HT room, so we'll see what wins...

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Lets see... calibrate a PJ or play with an Xbox... wow, that is such a hard decision. NOT! :rofl2:

koyalo said:

Question to Harpmaker - Do you have any plan for N9 or N8.5 mix? Also I would like to use Valsper paint...do you mind giving your HTS-X2(N8) formula for Valsper paint Or should I just bring your Behr formula and Lowes staff should be able to match the colors?

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First off, koyalo, welcome to the forum!

Yes, the mix series that HTS-X2 is a part of (to be called Elektra™) will run from N8.5 down to perhaps N7 (the bottom end is yet to be determined). It will be based on simply adding differing amounts of N6 gray paint to Cream&Sugar™, the more N6 paint added the darker the mix will be.

If you want a reflective N9 screen mix, this is already available in Cream&Sugar™. Check out it's thread here.

The amount of N6 paint to add to C&S™ to get Elektra™ N8.5 has yet to be determined, but it will be something close to only 1 or 1.5 fl. oz. per 48 fl. oz. of C&S™.

Please keep in mind that this thread is in the Developers Forum for a reason - the mixes are still in development.

I haven't had the N6 paint matched in Valspar paint yet, but I understand that Lowe's should have no trouble making it using the Behr tint formula, it all depends on the person behind the paint counter at Lowe's.

I am new member to this forum and very much inspired by your HTS-X2(N8) formula, its result and its simplicity. I would like to prepare DIY screen based on your formula but looking for N9 or N8.5 mix. My PJ is Mitsubishi HC3800 and I am not sure if N8 is too dark for it or not. My PJ is in basement and I am covering all my window to block all ambient light. Right now I am projecting on white wall but wanted to try out something different and better using your formula.

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Are all of your walls in the projection room painted white? How large is your screen?
Your PJ is a bright one so more likely than not a N8 screen would work for you depending on how large your screen is.

Appreciate your time and efforts. Keep up the good work!!!

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And we appreciate your taking the time to inquire into our screen mixes. :T

koyalo said:

Yes all walls are white right now including ceiling. I am first planning to prepare screen then later paint walls with dark color. I may left ceiling white for now.

I am projecting from approx. 15 ft and my screen size is 110 inch 16:9.

Which gray mix do you suggest for me? N8 or N8.5 or N9?

Appreciate your reply and suggestion! I will check out other links suggested by you as well.

-K

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With your PJ and screen size you are getting about 16 fL. of image brightness on your screen. This is enough to easily use a N8 screen even in eco mode. This is actually a bit more brightness than 1canuck2 has with his current setup, and he too went from a white screen to HTS-X2. He has been very satisfied with the white levels from the HTS-X2 screen while reaping the benefits of blacker blacks and richer colors from the gray screen. I would recommed a N8 screen.

I know this may seem like I am "straddling the fence", but some people just like a brighter image than others even at the cost of less image contrast. There is nothing wrong with this and if you fall in this group then a lighter N8.5 or N9 might be what you want, but I know I personally would prefer the N8.

Something I forgot to ask is how you will use your screen. Will you be mainly watching movies with all room lights out or do you watch a lot of sports with some room light on so people can safely move around without tripping? The less light in the room the lighter your screen can be, but if you need to have any other lights on a darker screen helps maintain image contrast.

I hope to get to a Lowe's store in the next several days so I might be able to get the tint formula for a N6 gray in Valspar. It will take longer to find exactly how much to add to C&S™ to make a N8.5 mix.

koyalo said:

Really appreciate your efforts. Your dedication is flawless... I wonder where do you get your inspiration from? :clap:

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I'm just one of those people that find all this stuff extremely fascinating and also enjoy sharing what I find out about screen performance with others. I found kindred spirits in the other moderators here in the Screens forum.

As far as I know, we are the only forum that is approaching screen performance from a scientific aspect and actually measuring screen attributes to the same standards as the commercial screen companies do. There is so much misinformation out there on how screens work it's sad.

Someone in another thread mentioned similar experience from Lowe's.

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I must have missed that one or simply forgotten it. The guy I talked to at Lowe's actually is quite knowledgeable about paints so if he was stumped I doubt any Lowe's store could recreate a Behr color just from the tint formula, which actually makes sense since different paint companies use different tints to comprise their colors. I was hoping that since all the paint stores I am familiar with use the same brand of "color computer" hardware and software (X-rite) that they could translate from one brand's tint formula to another's... guess not.

The sample of the Valspar match for a N6 gray cured enough so I could get a spectro reading and it isn't good. It is one of the few sample misreads I've gotten at Lowe's. I'll try again next time I get to a Lowe's. I hope to try the other Lowe's store that is "near" me (if you can call 35 miles away near - yeah, I live in the boonies), but it might not be in the near future due to the holidays coming up. There is a slim chance I might be able to do it tomorrow "if the creek don't rise".

This is a good example however of how one can't use their eyes to match colors accurately. Only the most discerning eye can see any color difference in the N6 sample and the Valspar match even when dry and side-by-side. When paint is still wet there is no way to accurately judge it's color to the tolerances we need for screens no matter how much "experience" you have. A good guess really isn't good enough.

1canuck2 said:

I went to buy the Behr the week after they'd pulled it from the shelf in my local HD. I had to drive to two different HD's to get the last remaining cans in the city... They have a replacement product that includes primer, but I don't know if Harp has had a look at them yet...

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Nope, not yet. Will get some today it the opportunity presents itself. I see no reason why the new Behr paint wouldn't work for our screen mixes since they don't depend on a large amount of translucency to work as some other screen mixes do.

Screen translucency is a two-edged sword in that while it allows any reflective particles in the mix to be more visible below the surface of the paint (which our mixes already achieve to a point since no paint we have found so far is totally opaque) it will soften and blur the projected image if carried too far. This is a concern with todays high definition PJ's. Back in the day when most PJ's were low resolution and/or had a visible "screen door effect" where you saw a grid pattern in the image if it got too large or you sat too close to the screen, those overly translucent mixes helped to give a better image due to their blurring effect. Those days are pretty much gone and those mixes are so yesterday. :bigsmile:

OK, you're not going to believe this... I did get to the other Lowe's store today and had my N6 sample color-matched again and even though the tint formula was different than the match I got at the other Lowe's it STILL isn't right! :hissyfit: The good news is that one or two more tries should get the correct color. I can only assume that there is a bug of some kind in Lowe's color-matching software; it isn't off color enough for most people to care, but when you're dealing with the level of precision that we are it does matter.

I also got to a Home Depot and now have a tint formula for N6 gray in a 8 fl. oz. sampler. This would do for making the Elektra™ N8.5 and Elektra™ N8 (also called HTS-X2) mixes. For making the darker Elektra™ mixes you would need to get a full quart of N6.

Even though this sampler is not the Behr flat latex Enamel it will do for coloring these Elektra™ mixes since relatively little needs to be added to C&S™ to darken it to the N8.5 and N8 shades.

Your question isn't dumb, K. Never be afraid to ask questions here. :T Things like color tint codes and formulae can be hard to grasp. We try to put our tint formulae in a form that can be printed out and handed to paint store personnel to have the paint mixed (although Lowe's wouldn't know what to do with a Home Depot formula). This refers to colors like the N6 gray and not a screen mix such as Cream&Sugar™ or Black Widow™, those have to be mixed by you.

I don't have a mix formula for Elektra™ N8.5 yet, but I could probably have one ready in 3 or 4 days. I know about how much N6 paint would have to be added to Cream&Sugar™ to make it, but I have to test a few samples to make sure.

As for how much mix to prepare, I suggest about 1 fl. oz. of mix per square foot of screen surface. Multiply the width of your screen in inches by the height of your screen in inches and divide that number by 144 to get total square feet. It's better to have too much than not enough.

The standard C&S™ mix makes 48 fl. oz. to which is added the N6 paint. In the case of a N8.5 Elektra™ mix I doubt more than 2 fl. oz. of N6 would be added to that 48 oz.. This should be more than enough for your 110" screen.

I'll post the complete formula for Elektra™ N8.5 when I have it ready. :T