Film-Tech Forum ARCHIVE: The latest "what is AMC doing wrong" query: high black levels

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Posted by William Kucharski (Member # 7246) on 08-15-2014, 03:27 PM:

I went to my local AMC last night and this particular theatre, while never the gold standard for projection, has Sony 4Ks that normally look pretty good.

However, last night, something was very… off. All normal black areas projected throughout, including trailers, displayed black as sort of a mid-tone grey rather than the as near "off" as possible blacks I've seen these same projectors throw many, many times in the past.

Of course the theatre manager denied anything was wrong, but presentation where it looks like a consumer projector with limited dynamic range is just weird coming from a Sony 4K.

FWIW, the film in question was The Giver, but the same too-light black areas were seen in the trailers as well as the AMC spots pre and post-show.

Any ideas what could be up?

Those familiar with NTSC video would recognize the effect as much the same as when feeding "black is 7.5 IRE" video to a display that expects it to be 0.

Could it be the projectors are set up to compensate for the light loss when showing 3D and are thus too bright when showing 2D? Or perhaps the last calibration was done with an older lamp and the projector was recently relamped?

Posted by Mark Gulbrandsen (Member # 72) on 08-15-2014, 04:55 PM:

Run.... It's a Sony!

Posted by Marco Giustini (Member # 4544) on 08-15-2014, 06:19 PM:

Bad mastering or faulty projector.
Many will disagree but Sony machines have better blacks than DLPs, even after years. It's a fact, it can be measured. Whoever says the opposite has never seen a Sony or has only seen faulty ones.
Sony have many downsides, but contrast ratio and black level are not one of those.

Posted by Brad Miller (Member # 2) on 08-15-2014, 07:04 PM:

Well yeah, you can take any projector and if it isn't putting out a bright picture the blacks will be blacker. [Razz]

I've actually never been impressed with an image from any Sony.

Sounds like there is something else going on with the machines William is referring to though since he said it used to be better.

Posted by Alan Gouger (Member # 543) on 08-15-2014, 07:11 PM:

I recently saw "Guardians of the Galaxy" in 3D at a AMC in Webster NY. They were using Sony SRX320s I was surprised how good contrast and black level appeared. I wasn't expecting much from the 320 knowing it is a generation older to the new 515. This AMC had the new motorized recliners.

Posted by Harold Hallikainen (Member # 5405) on 08-15-2014, 10:26 PM:

Are there automation cues for the motorized recliners?

Harold

Posted by Andrew Thomas (Member # 7000) on 08-15-2014, 11:36 PM:

I find the 320s to be supremely lacking in contrast and black levels, about the same as the .69 DLPs. The 515s are the new gold standard in contrast and black level to my eyes.

I saw Chef a couple of months ago on a 320 and the image was very washed out.

Posted by Monte L Fullmer (Member # 2797) on 08-15-2014, 11:57 PM:

Course, you can easily blame the washout due to the decaying LCoS chipset that Sony uses, where light passes through the chip and not reflected like the DLP setup.

Only time you get a decent 3D presentation out of a Twin Lens Sony Baloney unit is when the bulb has just been changed...and that's usually a Philips XDC-4200S lamp.

Give it a hundred hours and you have already lost 20 percent of your lumens, and three quarters of its life, the envelope is all but black and only one third of the available lumens are available.

If Sony would pick up on BARCO's CLO system, these lamps may have some decent light output throughout the life of the lamp. But Sony's blast theirs hot from the beginning which causes them do decay quite readily.

Posted by Buck Wilson (Member # 5885) on 08-16-2014, 12:29 AM:

Why doesn't anyone rag on Regal like they do AMC on here? Haha

Posted by Marco Giustini (Member # 4544) on 08-16-2014, 04:09 AM:

Brad,

Obviously I am comparing the systems when achieving the same brightness on screen. I said "black level" and "contrast". If you reduce the black level by reducing the brightness, the contrast ratio does not improve.

Monte,
I heard that too (decaying of the SXRD chips and high black level after a while) but it is simply not true. I've seen machines with 20.000hrs on them and the black level was still ok. Again, we can talk for days about downsides in a Sony machine, but picture quality is not within the list.

Ok, it can't be bad mastering since trailers were affected too.
If memory serves, range level can be set on the mediablock input too, and that could be set wrong. I'll check next time.

Posted by Jarod Reddig (Member # 6363) on 08-16-2014, 04:09 AM:

It could be as simple as a bad calibration with the black level set way too high.

Posted by Marco Giustini (Member # 4544) on 08-16-2014, 04:21 AM:

black level cannot be calibrated in a digital cinema projector (oh well, there is an option to input the black colour coordinates in DLP, not sure what they do). On a Sony you can choose the RGB level for DVI inputs and maybe for the server input as well - not 100% sure and it could be only with some sw versions, I'll check. If so, that could be the cause.

Posted by Carsten Kurz (Member # 5396) on 08-16-2014, 09:17 AM:

There is certainly a way to achieve this in the Sony setup software, but It's hard to imagine how this could have happened here, as this is a separate piece of software for the 320. It could of course be that there is a serious defect in the light engine. It's useless speculating. One could pinpoint the manager at the visible difference between two screens both using Sony and hope that he will be able to see and/or admit the difference as an issue, then give a call to service.

- Carsten

Posted by Mark Gulbrandsen (Member # 72) on 08-16-2014, 10:10 AM:

Marco,

I agree they can do black. But black Isn't worth the expense and hassle of having to put up with Sony and a poor quality image over the long haul. I' sure they are lucrative sites to service though.

Mark

Posted by Marco Giustini (Member # 4544) on 08-16-2014, 10:48 AM:

Mark,

I still don't agree on the picture quality issues. Everything else, I'm not arguing.

I don't meant to start a flame, but what is wrong in your opinion with SXRD's picture quality? We have assessed that black is not a problem. They are dimmer machines, sure. But as Dolby 3D, you just have to consider that when installing a big screen.
Brightness is a limitation, but not an issue.
What is wrong with the picture quality? I am genuinely asking, I am curious to know your opinion.

Marco

Posted by Steve Moore (Member # 4753) on 08-16-2014, 11:08 AM:

Any Sony installs I have seen look somehow, for want of a better word "fuzzy"; strange artefacts and an almost misty look to the picture. I think the old Christie Series 1 from what I have seen out performs in sharpness and wow factor; certainly considering that they are 2K. But that might just be the few sony's ive seen; I can't speak for them all

Posted by Steve Guttag (Member # 268) on 08-16-2014, 11:21 AM:

They never seem to get Green right...the color just looks "fake" for lack of a better description. I have NOT compared all models, however.

Posted by Marco Giustini (Member # 4544) on 08-16-2014, 12:59 PM:

I've never noticed that, I'll pay more attention next time. Corrected colours are always spot on, but it may be something else, after all colours are not just gamut.
Make sure you reset the correction, even though the projector is brand new. I have seen instances where the colour looked "fake" during calibration and resetting the calibration brought it back to what I was expecting.

I had the opportunity to compare a DLP to a 320 a few weeks ago. I managed to run the same clip from a feature and the 320 was way better in terms of contrast ratio.

Posted by Steve Guttag (Member # 268) on 08-16-2014, 01:15 PM:

DLP's contrast ratio is not their strong suit.

Posted by Monte L Fullmer (Member # 2797) on 08-16-2014, 01:47 PM:

Granted, you shoot an image on a screen, coming out of a 320, which is less than 40 ft wide and a throw over 70 ft using an USHIO 3k bulb and you do have a very nice picture.

Posted by Connor Wilson (Member # 6088) on 08-16-2014, 04:04 PM:

Last movie I saw on a Sony unit was Guardians of the Galaxy, in 2D from a 320 projected on a common width screen. It wasn't as impressive as the same movie from a Barco unit in Dolby 3D, common width screen.

I actually compared (not directly) The Lego Movie between a 515 and a 320 in the same complex, both in 2D. The 320 had a misty look, while the 515 was crisp and clear.

I was impressed by 515 married with RealD 3D when I went to see Dawn of the Planet of the Apes. The screen was common height, and it was a shorter throw. And this was an AMC where they played the "See more trailers..." snipe before the trailers and the Coming Soon snipe after the trailers.

Posted by Marco Giustini (Member # 4544) on 08-16-2014, 05:01 PM:

You can't compare a 2D with a 3D picture!
The 515 has a massive contrast ratio and a very low black level. But to be honest I don't see the 'mist' on the 320 I see around. I would be more probe to blame the auditorium (bright walls, dirty porthole, dirty lens).

Posted by Monte L Fullmer (Member # 2797) on 08-16-2014, 05:47 PM:

Doesn't the 515 have about a 10,000:1 contrast ratio?

Posted by Marco Giustini (Member # 4544) on 08-16-2014, 06:03 PM:

8000:1 on the datasheet

Posted by Steve Guttag (Member # 268) on 08-16-2014, 09:21 PM:

And with a checkerboard pattern?

Posted by Marco Giustini (Member # 4544) on 08-17-2014, 05:34 AM:

I've never tried that, but you'd need a perfectly black auditorium to take a meaningful measure. You could turn the meter towards the projector, but my meter does not allow that.

In the real world I've measured on/off 4000:1, but, again, the auditorium was not pitch black.

Posted by Carsten Kurz (Member # 5396) on 08-17-2014, 06:21 AM:

Not a single projector in the world goes above 1:600 to 1:700 with a checkerboard/ANSI measurement, and even that only under experimental/bat cave conditions. All contrast numbers above that are on/off or 'sequential contrast'.

It's quite typical for pro and home projectors that DLPs shine in ANSI, but suffer in sequential contrast, while e.g. for LCoS/SXRD the achievable ANSI is lower and the sequential contrast is higher.

This is not an exclusive ANSI/sequential behaviour - these weaknesses or strengths operate through all typical varying image types/amounts of bright/dark in images. So, the darker the image, e.g. night scenes, the better the SXRD will perform, while in evenly, bright lit scenes the benefits of the higher ANSI contrast of the DLPs come out.

It's just that you don't perceptually weight an ANSI/in-picture contrast difference between say, 1:300 and 1:500 as much different, while an on/off contrast of 1:1500 or 1:5000 makes all the difference.

It probably wouldn't be so important if not film makers nowadays would choose to underlight scenes or use available light a lot more than they used to 20-30 years ago. The amount of image parts lying in shadow is much higher nowadays. And that plays towards the need for higher on/off or sequential contrast, because you don't want large areas being ripped up into greyisch-brownish noise. Something seen very often with the S2k and 4k DLP chipsets (lens quality and apertures used/not used being an issue as well).

Everyone knows that even a mediocre LCD presentation projector can look good with a nice, bright, evenly light picture. The trouble comes with the shadows and high contrast imagery.

Most manufacturers, even in the Pro business, prefer to give on/off contrast numbers, simply because they are always higher than ANSI contrast numbers. ANSI/checkerboard is only one defined measurement method for in-picture contrast. You could easily get very different numbers if you change the measurement pattern into something with different areas/amounts of black and white. So, as a matter of fact, the in-picture contrast of every projector is different for all occurring images/footage that runs through the projector. It's a moving target. On/Off contrast is independent of image type/footage, but is not really a practical measurement, but gives an indication on the achievable 'darkness' a projector can produce under static conditions.

Some DCI-type DLPs can be modified with aperture plates in the projector and/or in the lens. I think you can increase on-off contrast towards something like 1:3000, but it maxes out around there (ANSI will also improve). But it eats a lot of light, so this is nothing for the bigger screens.

In most real-world conditions, due to ambient/exit and emergency lighting, achievable ANSI/in-picture AND sequential/on-off contrast is much lower than above quoted numbers - typically not even higher than 1:100 to 1:200.

- Carsten

Posted by Marco Giustini (Member # 4544) on 08-17-2014, 07:12 AM:

I firmly believe that both figures have to be taken into consideration. on/off contrast (which for a 14fL picture basically tells us the black level) is important but ANSI is important as well. If ANSI is low, the black level figure will disappear as soon as a candle appears on screen.
I did not know that SXRD were lower in ANSI. But as you say it is not easy to measure - should do that in a bat-cave to have meaningful results.

As a reference, high end home theatre projectors can achieve 30.000:1 on/off contrast ratio. Dark sequences look amazing, but bright ones look so washed out.

Posted by Ken Lackner (Member # 1002) on 08-18-2014, 10:32 AM:

quote: Monte L Fullmer
If Sony would pick up on BARCO's CLO system, these lamps may have some decent light output throughout the life of the lamp. But Sony's blast theirs hot from the beginning which causes them do decay quite readily.

I'm not sure where you got that from, but it is entirely false. Sony projectors most certainly do have a method of maintaining even light output by automatically adjusting the current throughout the life of the lamp. Of course, as with any projector, to take advantage of this feature requires headroom. That is, if you must run a brand new lamp at 95% or 100% to get the required light on screen, you have no room to increase the current and the light output will definitely decrease over time.

If you encounter a projector that is running a lamp at 100%, that's because the installer set it up that way. (Probably because the screen is too big for that projector, but that's not the projector's or installer's fault.)

Posted by Carsten Kurz (Member # 5396) on 08-19-2014, 05:23 PM:

Indeed, both the 320 and 515/510 have switchable direct power, or constant luminance lamp control through an internal sensor, just like the DLPs do.

- Carsten

Posted by Marcel Birgelen (Member # 6801) on 08-20-2014, 03:16 AM:

quote: Monte L Fullmer
Course, you can easily blame the washout due to the decaying LCoS chipset that Sony uses, where light passes through the chip and not reflected like the DLP setup.

LCoS or Sony's implementation called SXRD uses reflective technology, just like DLP. The difference is that DLP is a matrix of tiny switchable mirrors and LCoS is essentially a mirror with a thin LCD layer on top of it. So, the light would only pass trough this very thin layer of LCD. Maybe this LCD layer wears out over time, due to the excessive heat it has to endure, but I doubt that it would result in a problem as being described here. This problem feels more like a calibration problem or maybe there was another light source illuminating the screen? I've had a curious case where someone left on a projector used for some kind of business presentation, projecting some kind of blackish image and washing out the 35mm picture...

Actually, you could suspect that the "blackness" of DLP also washes out a bit over time. Modern DLP chips have their "backside" coated in some kind of black/light absorbing substrate, but if you have ever witnessed what the excessive heat does to the heatsinks in your DLP light engine over time, you could argue that this substrate will also evaporate/burn away over time, causing more light to leak trough.

In general, you would expect the DLP technology to have a better contrast ratio, because it actually diverts the light into heatsinks using those switchable mirrors. Still, even with all the mirrors in the "off" position, there is a considerable amount of light leaking trough.

Curiously, the best "true black" representation using a checkerboard pattern I've seen, without the use of auto-iris or other tricks came from a JVC projector using their version of LCoS called D-ILA. Unfortunately, nobody is currently planning building DCI equipment based on that technology.

Posted by Jarod Reddig (Member # 6363) on 08-21-2014, 04:27 AM:

The D-ILA JVC's are the best I've seen in that performance area as well.

Posted by William Kucharski (Member # 7246) on 08-21-2014, 07:34 PM:

To bring this all back full-circle, what's the easiest way their black levels could have gotten off given they likely don't recalibrate frequently? My guess was that they did an autoconfiguration of brightness levels with an old bulb and relamped, but there has to be some answer as in general theatres in the same area tend to be calibrated by the same people and other AMCs here don't have this issue with their theatres and this one didn't have this issue in the past.

BTW, I am very, very impressed with the JVCs.

Posted by Marcel Birgelen (Member # 6801) on 08-22-2014, 04:17 AM:

It's really hard to guess, because there are so many things that might have caused this.

How did it look in between trailers? There probably was a format change, since The Giver is in scope, how did it look before/after/during format change?

Does the theater have movable masking? If it didn't, how did the edges look? Was there a distinct runoff in brightness?

Did you check if there was another ambient light source in the theater? Someone leaving the lights on in the booth? (Although that would probably not result in a uniformly brightened screen, but a few irritating bright spots.)

Posted by Marco Giustini (Member # 4544) on 08-22-2014, 05:36 PM:

Again, there is no calibration for black on a D-Cinema projector. There may be an option to tweak the brightness on the Server input - can't remember on top of my head - but it should not be used and it is not meant to calibrate anything.
Lamp alignment does not change black level either (well, if you raise the brightness, the black level will increase but that's not the point).

Posted by Marco Giustini (Member # 4544) on 08-24-2014, 03:41 PM:

D-ILA are truly great at blacks but ANSI - on consumer machines - is poor. It would be interesting to see a D-ILA with a pro light engine and lens.
You can measure 30000:1 with no iris or tricks. But then ANSI goes down to 100:1 - which is still very decent, don't get me wrong!

(my apologies for the double post, I found this on my laptop, I was writing it when the battery died. And I posted it without checking first the status of the thread)

Posted by Carsten Kurz (Member # 5396) on 08-24-2014, 05:05 PM:

It's not that bad, Marco, e.g. recent JVC D-ILAs show ANSI contrast into the 1:300 to 350 range. Even in optimized screening rooms, the visible difference to 1:500 to 1:700 of single-chip DLPs is barely there, so they offer both a very good in-picture contrast as a very high on/off contrast.

But these machines are optimized for black level/contrast, they have a comparably low light efficiency.

- Carsten

Posted by Marco Giustini (Member # 4544) on 08-27-2014, 10:17 AM:

Carsten,

ANSI contrast is never measured unfortunately, can I ask you where did you find those values? Not that I don't believe you, just want to confirm the source.

I personally measured 1:126 on one, but that was years ago.

Back IT: Yes, the 320 have a "limited/full" RGB level option on the Server input - not sure for what reason - but the server works on "full", so the wrong one will provide crushed blacks, but not washed out images.

However, the same input has also the option to tweak brightness and contrast. The default levels are not "zero" and if you raise the brightness you raise the black level indeed.

I don't really know what those controls are doing in a D-Cinema projector, but as far as I know they shouldn't be touched. If someone did it, I would blame the installer and not the projector.

Posted by Carsten Kurz (Member # 5396) on 09-08-2014, 06:17 PM:

Here is a thread summarizing measurements on some prominent and well performing home video projectors.

As you can see, these numbers reflect my statement from above, that DLPs shine in the ANSI contrast field, while LCoS/SXRD and optimized LCD achieve higher on/off contrast.

The test patterns used are also shown. When you understand the effect of stray light and the difference between ANSI and on/off, it can easily be understand that the EBU test pattern gives results somewhere between ANSI and on/off or 1% white.

Most values have been measured without dynamic iris or light modulation techniques used in many projectors to improve on/off contrast or black level.

http://www.hifi-forum.de/index.php?action=browseT&back=1&sort=lpost&forum_id=94&thread=13598

- Carsten

Posted by Marco Giustini (Member # 4544) on 09-09-2014, 01:21 PM:

My German language skills are not great (I don't speak a word) but that seems very interesting. I know that old DILA were not going any further than 150/200:1, it's great that recent ones have improved. I believe I measured 500:1 on a series 1 DLP.
I'll ask Google to help me on that thread! [Smile]

Thanks
Marco

Posted by Carsten Kurz (Member # 5396) on 09-09-2014, 02:09 PM:

Yes, recent LCoS/SXRD have improved a lot in ANSI contrast, some come close to DLPs.

- Carsten

Posted by Mark Strube (Member # 4190) on 09-10-2014, 07:56 PM:

Could be as simple as port glass that hasn't been cleaned in a very long time... dust and dirt buildup will give a very glowy look that will cause black areas of the picture to appear lighter when it's not a 100% black image.

Posted by Marco Giustini (Member # 4544) on 09-11-2014, 03:25 PM:

in a very long time = since installation time. It's the norm. Many are simply not accessible on the outside and not removable on the inside -> they never get cleaned.

Posted by William Kucharski (Member # 7246) on 10-02-2014, 03:58 AM:

Just as an update - I spoke to the GM of the theater rather than the night manager, and a week later, whatever was wrong was fixed.