HTS-X2 - an experimental N8 reflective screen mix - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 92 Old 11-29-09, 08:11 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

Those are some pretty amazing shots 1C2! Thanks!

I have to ask, how close are the photos to what the image looks like on the screen with your eyes?
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post #12 of 92 Old 11-29-09, 09:47 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

I'd say they are pretty close. The only pic that doesn't look quite as good is the Leeloo falling one which in the pic looks more "edgy". Perhaps the freeze frame betrays the special effects more for that shot...

The Nemo and Bolt ones a pretty spot on.

The photos are completely untouched. I did the custom white balance, used a 2 second timer with the camera on a tripod, took the pics on Fine at 4000 x 3000 and then uploaded them straight to PhotoBucket which resizes them with whatever method PB uses.

Oh, and I will pop the sample card I painted for you in the mail tomorrow so you should have it by end of week... I am interested to see what your analysis shows.

Last edited by 1canuck2; 11-29-09 at 09:55 PM.
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post #13 of 92 Old 11-30-09, 04:50 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

Vey nice screen shots.....contrast looks fantastic!
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post #14 of 92 Old 11-30-09, 07:42 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

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Vey nice screen shots.....contrast looks fantastic!
Very nice indeed! I'm still blown away by them.

A major component in these photos is that the PJ was calibrated to the screen (which is D65 neutral) and the camera was white balanced to the screen with a white image being projected.

The reason, IIRC, that 1C2 went with the N8 screen was to improve image contrast and black levels over his white screen. I would say it worked!
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post #15 of 92 Old 12-01-09, 07:16 AM
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Re: HTS-X2 - an experimental N8 reflective screen mix

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Uh, dumb guy alert. You are going to have to explain a little more clearly what you want me to do... sorry
the measurements you have taken are with the colorimeter pointing at the screen.

what Mech has asked for is for a second set of measurements with the colorimeter pointing directly at the PJ. the second set is used as a baseline measurement and helps us see if the screen is causing a color push.

i have an i1 display and it freezes when taking direct readings from the screen. hopefully you dont have the same problem.
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post #16 of 92 Old 12-01-09, 08:15 AM
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Re: HTS-X2 - an experimental N8 reflective screen mix

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Harpmaker wrote: View Post
Very nice indeed! I'm still blown away by them.
Well the thanks goes to you... you gave me the formula. I just did the grunt work.

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Harpmaker wrote: View Post
A major component in these photos is that the PJ was calibrated to the screen (which is D65 neutral) and the camera was white balanced to the screen with a white image being projected.
The pictures came out better than any other's I have taken, which never seem to do the real world experience justice, I think the white balance idea was the clincher. I would say they are pretty close to what I see with my naked eye. Nemo, especially, looks superb.

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The reason, IIRC, that 1C2 went with the N8 screen was to improve image contrast and black levels over his white screen. I would say it worked!
This was indeed the reason. I had two goals.
1. For relatively little investment, get a screen that would perform as well as, if not better than, something I'd have to spend $1K+ to achieve if buying a "real" screen. I feel this is achieved. The results have more than exceeded my expectations.
2. Be able to handle a little ambient light for when we play Wii and still have the colours look decent.

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custard wrote: View Post
the measurements you have taken are with the colorimeter pointing at the screen.

what Mech has asked for is for a second set of measurements with the colorimeter pointing directly at the PJ. the second set is used as a baseline measurement and helps us see if the screen is causing a color push.

i have an i1 display and it freezes when taking direct readings from the screen. hopefully you dont have the same problem.
Thanks custard. I PMed Mech for some specifics, so now I just need to do it. I am using a Spyder3, so we'll see how it goes. A couple of times when doing 0 IRE readings for the grayscale, the Spyder and/or HCFR froze up, it doesn't do well in low light, but I have never tried blasting it with the light directly from the PJ.
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post #17 of 92 Old 12-04-09, 06:42 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

Sorry for the tardiness. I was off work today so carved out some time to do the readings Mech requested. Hopefully done correctly!

In the attached zip file should be two files:
ProjReadings.chc - HCFR readings for Greyscale, Primaries and Secondaries with the Spyder3 roughly halfway up the screen, about 5 inches from the screen, angled toward the projector lens. (I took realtime readings and fiddled with the angle to tweak the highest ftL)

ScreenReadings.chc - HCFR readings for Greyscale, Primaries and Secondaries with the Spyder3 just below halfway up the screen, about 12 inches from the screen, angled toward the halfway point of the screen. (I took realtime readings and fiddled with the angle to tweak the highest ftL)

I don't really know what I am looking it in truly analyzing these files, so I'd appreciate some "here's what you discovered" type summary after you've analyzed them, if only for my own learnin'.
Attached Files HTS-X2 Readings.zip (5.3 KB) 
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post #18 of 92 Old 12-05-09, 01:50 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

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Basically, all we're doing is comparing the two. The readings from the pj is what is hitting your screen. And the reading from the screen is what is reflected back. If there's a difference between the two, the screen is affecting the image. If it's a big difference, as I've seen with some things, it may be detrimental to the effect of not being a viable solution.
This part makes sense. Using computer numbers, if I shoot a 255,128,0 and get back a 249,128,0 then the surface I am shooting on is "absorbing" 6 points of red and is thus not completely neutral.

My original question is more understanding the significance of the various graphs available in HCFR.

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My initial look at the numbers shows me very little difference between the two readings. I see a very slight drop in blue, but nothing significant. Looks good so far!
Good example, in one of the graphs I did see a difference in the blue line from the two different sets of readings.

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Also, I disregard all of the readings below 30IRE. I'll have more for you later this evening when I have a bit more time to look at these files.
Good, cos I notice the numbers are all over the place at lower IRE. Is that that simply because the Spyder3 is not good at low IRE? I assume the super-spendy colorimeters do better at low light.

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?

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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post #19 of 92 Old 12-05-09, 06:41 PM Thread Starter
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Re: HTS-X2 - an experimental N8 reflective screen mix

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1canuck2 wrote: View Post
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?
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.

Quote:
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...
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.
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post #20 of 92 Old 12-05-09, 07:00 PM
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Re: HTS-X2 - an experimental N8 reflective screen mix

Wow! Detailed explanations guys. I warned you I was ignorant to the complexities of the issues at hand. I knew the gain crazy folks were off the mark, more because they didn't seem to care about other factors that would seem as important, if not more. As I said before, that's how I found my way over here from AVS.

I am certainly extremely happy with the results of my screen. I am guilty of buying a PJ without considering my room first, but also think I have ended up with an apporpriate PJ all the same since I have good light control and a powerful PJ (Epson 6500UB). Thankfully it also has a good CMS, so I have been able to tweak out any potential non-neutral quirks from HTS-X2, but the final verdict on that is now down to Mech. Whatever your results, I don't fele compelled to change anything as the screne more than meets my expectations. So unless you have some numbers that show me something is way out of wack, I'll consider myself done.

BTW, I forgot to mention, my PJ bulb only has 90 hours on it. As bulbs age, do they typically change their colour representation, or just get dimmer?

Thanks again. I am looking forward to Mech's assessment.
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