Film-Tech Forum ARCHIVE: Real D 6fl -- do I want it?

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Posted by Frank Cox (Member # 6258) on 10-24-2014, 04:40 PM:

The tech who does the work on my setup was just here to do a general tune-up of my system (re-balance the sound and colour, change filters, etc) and he told me that I have enough light on my screen that I could play the 3D 6fl features if I want to. Unfortunately, I didn't follow up on that with him, so now I have some questions to ask here:

I have a Christie 2210 with a Real D Z-screen setup.

1. Do I want to play 6fl 3D instead of the 3.5fl versions that I've been playing up to now? What would I gain?

2. Do I have to make any changes to the setup if I do want to play the 6fl versions, or is it just a matter of putting the 6fl version of the movie in the playlist and hitting play on the server? I have cues set up for 2d and 3d, would I need a different cue of some sort for 6fl 3d?

Posted by Marco Giustini (Member # 4544) on 10-24-2014, 04:58 PM:

ask him to do an average. You will likely find that you are nowhere near 3.5fL, more likely 1.5fL or less.

And where the 3.5fL figure is coming from? It should be 4.5fL but latest DCI say 7fL.

I'd go for the brightest you can afford.

Posted by Frank Cox (Member # 6258) on 10-24-2014, 05:05 PM:

The 3.5 figure came from me. Perhaps I've got it wrong and it should be 4.5.

Really, all that I really know at this point is this: He set up one of those fancy USL camera doodads in the aisle and was fiddling around with the colours and whatnot. He said, "There is enough light on this screen that you can play 6fl 3d on it if you want to."

And that is the entire extent of what I know about it.

I've been playing "regular" 3d on it up to this point; never even considered playing the "brighter" version since I didn't think I could do it. Now I'm wondering if I should be playing the 6fl versions, and what it would take to be able to do that, if anything.

Posted by Sam King (Member # 4029) on 10-24-2014, 05:17 PM:

I was told that to play the "Bright" version, you had to have an XL unit, no Z screens, regardless of how bright.

Posted by Carsten Kurz (Member # 5396) on 10-24-2014, 06:29 PM:

Which lamp power setting do you use for 2D and 3D?

First of all - what you say in your second post seems to suggest your tech measured around 6fl for 3D. He did not suggest to set your system from 3.5/4.5fl to 6fl.

That may mean - your screen/lamp is currently slightly brighter than most 3D movies are graded for.

Given the typical variations, lamp aging, etc., your patrons will probably benefit more if you continue to play 3D movies mastered for 4.5fl at 6fl.

There is not such a great difference as you may think. I would think you need to get separate KDMs for the 6fl DCPs, if you are not already receiving combination keys for both gradings. Anyway, you could give it a try, you can revert to 4.5 DCPs any time. Just tell the distributor you are back at 4.5fl. There is no major implication with this. You don't need to make any adjustments or change cues. Just select the 6fl CPL if you have the key for it.

The tech may also have meant that your bulb has enough headroom to aim for 6fl. That would mean, you have to increase the lamp current before you should play the 6fl CPLs.

- Carsten

Posted by Steve Guttag (Member # 268) on 10-24-2014, 09:08 PM:

If you are capable of playing at 6fL (throughout the life of the lamp on your largest format)...then that IS the way you want to go. The 6fL version will have more contrast so the brights can look brighter without the blacks looking washed out.

And it does not matter what form of 3D or apparatus you use...that is you can do 6FL on either a Z-screen or XL.

Posted by Frank Cox (Member # 6258) on 10-25-2014, 12:22 AM:

Thanks for the information! I feel a lot smarter now than I did earlier today.

I guess the best way to find out what's what in this regard will be to simply wait until the next time I have a 6fl 3d movie, try playing it and see what it looks like. If it looks good, great; I'll use that one. If not, I've lost nothing but ten minutes of experimentation.

Posted by Monte L Fullmer (Member # 2797) on 10-25-2014, 01:52 AM:

Yes, you will need separate 6FL (or, the content can be labelled XLBRITE) keys to play the 6FL content.

When you receive the content that contains both versions, you will receive both, the 45FL (or just standard 3D) and the 6FL keys of you choice to use.

-Monte

Posted by Carsten Kurz (Member # 5396) on 10-25-2014, 05:11 AM:

quote: Frank Cox
I guess the best way to find out what's what in this regard will be to simply wait until the next time I have a 6fl 3d movie, try playing it and see what it looks like.

Try to get both the 4.5fl and 6fl keys and compare. Next time you should get more information from the tech - that his, what luminance did he measure, what type of bulb is installed, how many hours on the bulb, which lamp currents for 2D and 3D.

If in fact you have a new bulb running at 90% or above and achieve 6fL center, I wouldn't choose to run 6fl DCPs and stick with the 4.5fl.

- Carsten

Posted by Jarod Reddig (Member # 6363) on 10-25-2014, 08:16 AM:

Does one need brighter 6fl 3D? The answer will be yes and it will still look dim. We need 14fl.

Posted by Marco Giustini (Member # 4544) on 10-25-2014, 08:38 AM:

Carsten,

If you don't want to run your lamp at 100% to achieve 6fL, you can run the lamp slightly lower and run your 3D at 5.5fL!

The 4.5/6 fL are not magic numbers, running your 3D a little brighter won't spoil your presentation - actually it is the contrary. And as I said on a Silver screen the centre brightness number does not usually make any sense.
I've measured a screen the other day where the owner said 2D looked dull. Silver screen on flat frame with short throw. Massive hot spot on centre and that's it. Centre measured 13fL. It's within DCI specs, so why the picture looked so dull?
Because left side (not the very extreme BTW) measured 2.44fL and the right measured 4fL. If you do a quick average you will find that to have an average of 14fL, you'll end up with more than 20fL in the centre of the screen.

Posted by Steve Guttag (Member # 268) on 10-25-2014, 11:28 AM:

The DCI/SMPTE specs do NOT just specify the center brightness...there is also the side/corner measurements that are required to be met to meet DCI/SMPTE specs. So just going for 14fL Center (or 4.5 - 7fL, depending on the 3D title) is NOT sufficient.

That is why, with a silver screen (or most high gain screens over 1.3 gain) the image will actually appear darker if just the "center brightness" is set. The only way to increase the gain on the sides/corners is to curve the screen in proportion to the gain (which sets is relative reflectivity/fall off angle).

Posted by Marco Giustini (Member # 4544) on 10-25-2014, 01:41 PM:

exactly, but that seems an unknown concept to most people, they just point the meter to the centre of the screen, dial 14.0fL/4.5fL and walk away.

I've only seen one auditorium with silver screen and a very even brightness. I did not want to believe it. The brightness was indeed within +/- 10% (centre/sides).

Posted by Carsten Kurz (Member # 5396) on 10-25-2014, 02:45 PM:

quote:

If you don't want to run your lamp at 100% to achieve 6fL, you can run the lamp slightly lower and run your 3D at 5.5fL!

Of course, Marco, but the question was not how bright he would actually run in 3D, but wether the brightness he achieves over the usable time span of the lamp (with lamp aging and side falloff, etc.) qualifies to play 6fl DCPs in the future. Of course he could run 6fl DCP for as long as his lamp yields, and then fall back to 4.5 versions. But I'm sure this is not what Frank was after.

Wether he should run 6fl DCPs or 4.5 fl DCP when he is actually able to achieve 5.5fl - I guess I would still opt to play the 4.5 DCP for the various reasons already mentioned.

In short words - what the tech said is not enough to give a useful advise.

If I'd had a tech in for money and part of his job would be to measure screen brightness, I would expect a file or prinout with the necessary details of his measurement given. And that needs to indicate at least format (flat and scope), type of bulb, age, lamp current set during the measurement together with each brightness measurement.

As this is a RealD system, one should also expect to have the sides/corners measured. It doesn't take much time to do a series of measurements once everything is set for it.

- Carsten

Posted by Marco Giustini (Member # 4544) on 10-25-2014, 05:05 PM:

Has anybody ever compared a 4.5 with a 6fL version btw? I doubt they would show much difference.

I also doubt that there are cinemas around the world where brightness is properly set and *maintained*. Too many variables, unless a technician is on site.

I feel the answer to Frank's question is just "yes", I don't think that a file is needed to answer that question, particularly when we are talking of a silver screen.

Posted by Carsten Kurz (Member # 5396) on 10-25-2014, 05:24 PM:

If you actually show 3D at 4.5fl, every possible improvement is probably worth thinking about. But without real numbers...

- Carsten

Posted by Marco Giustini (Member # 4544) on 10-25-2014, 06:35 PM:

what numbers would you need? Whether it's 4.5 or 3.5, averaged or just centre, 6 is the bigger number and I would go for it (or whatever number my lamp allows without trashing it at 100% from day one) without thinking it twice.

Posted by Carsten Kurz (Member # 5396) on 10-26-2014, 07:27 PM:

Marco. sigh.... If the tech says that Frank could play 6fl mastered 3D DCPs, this can have two meanings:

- his projection is already 6fl in 3D
- his projection is below 6fl in 3D, but his lamp has enough headroom to go for 6fl

Now what is it? What other than 'a meaningful number' will let us or him know?

A tech taking screen brightness measurements with the result that Frank could play 3D features mastered for 6fl?

No that's a strange way to tell the results of a screen brightness measurement.

- Carsten

Posted by Marco Giustini (Member # 4544) on 10-28-2014, 08:58 AM:

Ok, I missed that it was not said whether that was a possible upgrade or something already in place.

I feel there has been a misunderstanding though, I am not expecting a tech to provide sheets or anything fancy, just to ask "I can set your 3d brightness to 6fL so you can play 6fL DCP's, would you like that?".

Any chance that whoever dealt with the tech did not know what that meant and the tech just decided to leave the default brightness?

That is where my post was coming from.

Posted by Marcel Birgelen (Member # 6801) on 10-29-2014, 03:57 AM:

quote: Marco Giustini
Has anybody ever compared a 4.5 with a 6fL version btw? I doubt they would show much difference.

Doing a side-by-side comparison isn't particularly easy, so you're relying on your memory more than on some real hard facts. The way humans perceive "brightness" also isn't helping too much.

Like Steve already indicated, the 6fl versions seem to have more contrast. You will notice this in the darker parts of a movie, not so much in bright daylight scenes, at least that's how it looks to me. Since you cannot just open this file on your computer and do a frame-by-frame comparison, it remains a rather subjective assessment.

Maybe someone who actually is involved with the creation/mastering of mainstream feature 3D DCPs could shed some light on what differences actually exist and if this process is uniform across releases or being "fine-tuned" per release.