Calibrating for video accuracy

[Steve Kalle]

To get past the thought that software can make a display "accurate", realize that a monitor emitting light is a PHYSICAL property which is dictated by the Laws of Physics. The liquid crystals or diodes can emit light only so accurately and the backlight essentially controls how accurate the display can be. The quality of the backlight explains why the same IPS panel being used in $400 Dell/HP LCDs and my $2500 Eizo have such large differences in accuracy.

The sad thing about all of this is the iPad 3 for $400+ has a more accurate screen than most $2000 monitors AND its higher resolution.

FYI, I use Premiere and have my Eizo connected via DP to a Quadro FX3800, which allows me to display YUV or RGB natively as well as 10bit (but this is on Win7 and Premiere is not 10bit capable on Mac).

Search for the article on provideocoalition about Premiere CS5, DisplayPort and RGB/YUV - its also linked several times by other members here. It will explain why you would need an I/O card/box and 3rd monitor versus why you can do what I do. However, I do have a BMD Decklink Extreme 3D and a Panasonic 1710w.

[Will Thompson]

Steve, thanks for the PVC article. Here is the link for anyone that doesn't want to search:

ProVideo Coalition.com: TecnoTur by Allan Tépper

Just to clarify - I did not mean to imply that I think software can make any display accurate, only that software calibration can be just as accurate as hardware. Cheap-O Monitor X will look no better connected to a calibrated IO box than through properly color managed software.

What I gather is that FCPX is currently the only fully color-managed NLE, so it's the only NLE capable of rendering its preview output corrected for YUV *and* adjusted for a display profile. However, it appears that OSX's GDI is limited to 8-bit, so that could be a major drawback for some. It's hard to find information on this.

Premiere CS5/CS6, as I understand it, will preview accurate YUV/RGB conversions in 10-bit (in Windows with a 10-bit graphics card), but does *not* adjust for a display profile, and instead just assumes sRGB. So it will be as accurate as your display handles sRGB natively, but if you create a display profile using a colorimeter, those adjustments won't be accounted for in Premiere. However, it appears that SpeedGrade has the ability to import a color profile and use that as a LUT for grading. It seems like this could get you closer to what ColorSync does for FCPX, but I haven't found much else about it.

If I got any of this wrong, please let me know. I'm just trying to understand the cost/benefit to see where I should spend my (limited) resources.

[Steve Kalle]

You are mixing up ICC profiles normally used for printing and calibration for video which is a 1D or 3D LUT.

When calibrating a monitor in software-only mode, the calibration is applied through the graphics card and its always 'On' unless you tell the software to disable it or change to another calibration. In 'Hardware' calibration, the monitor stores and applies the calibration settings so you can connect the monitor to anything and the calibration settings can be used independent of the source.

Also, Premiere would never use sRGB because Rec 709 is the default color space used in most programs & devices (HD video is Rec 709 whereas Rec 601 aka SMPTE-C is SD broadcast).

Btw, calibrating to Bars is an old way that has been used to get a 'close enough' setting where colorimeters cannot be used (too expensive and/or most monitors don't support hardware calibration).

From what I recall during the first several months after release, a major drawback of FCP X was the inability to use a properly calibrated reference monitor.

Generally speaking, the use of display profiles in video editing, vfx, 3D and animation is to have each person's monitor within the pipeline appearing as similar as possible to one another, eg. the compositor applies a LUT so he can see how the end product will look .

[Sareesh Sudhakaran]

Originally Posted by Will Thompson

...only that software calibration can be just as accurate as hardware.

Software, even prosumer ones, are already light years ahead of hardware. As a closet programmer, I always have to get software to 'dumb down' to accommodate hardware.

Practical colorimetry is based on human feedback, like for example CIE 1931/RGB. Software needs a feedback loop, it can't 'see' for itself.

E.g., if I build a new display and connect it to software, FCPX, Premiere, whatever - how will the software know what the display is outputting? The display's feedback data might say Red, but the monitor might actually be showing something else. This is why one needs a calibration tool. Even with the tool, the unique features of my monitor's gamut will render the software useless, unless -

As in my previous answer - it can 'keep an open mind' and 'get a bigger math boat' - which 32-bit does well enough, with 'float' being a sufficiently acceptable mathematical compromise.

Think of an NLE or grading tool as a sheep pen. The best it can do is to be as wide as possible and have the highest walls - the sheep are the algorithms that can go beserk sometimes - the walls (color space/model/gamut) keep them in, the size of the grounds (the math base) keeps them happy and healthy.

The weak link in the chain is the human. No two humans will see the same color, even under the exact same conditions. To make matters worse, an individual can look at one color at 2 pm and again at 5 pm and they will look different. The same is true of a display - it's a physical system whose properties change due to thousands of reasons.

At best, it's a fuzzy relationship. Software and hardware need human feedback to be accurate. Humans think hardware and software will do the job, and he/she can keep their eyes closed.

I would sincerely warn anyone of using their monitor as the benchmark or standard, even if the monitor is a DI grade P3 projector. My experiences indicate (at least to me) that following simple color space standards and judging with your eyes is the right way to go, and that monitors just have to get with the program.

[Will Thompson]

Originally Posted by Steve Kalle

When calibrating a monitor in software-only mode, the calibration is applied through the graphics card and its always 'On' unless you tell the software to disable it or change to another calibration.

Right, calibration is always on, but non-color managed apps typically assume the monitor is targeting sRGB, regardless of the actual target. A color managed app will know this and compensate to generate the correct output, while a non-color managed app will map to the wrong colors if your display profile doesn't target sRGB.

Originally Posted by Steve Kalle

Also, Premiere would never use sRGB because Rec 709 is the default color space used in most programs & devices (HD video is Rec 709 whereas Rec 601 aka SMPTE-C is SD broadcast).

My understanding is that Premiere does not target sRGB, but it assumes your monitor is targeting sRGB, not Rec 709, and corrects from there. If you target Rec 709 during calibration, then Premiere will be overcorrecting the image because it is not color managed and has no knowledge of your display profile.

[Roger Van Duyn]

Right now I don't have the funds to purchase the necessary hardware to get the 709/yuv preview from my PC to an external monitor. I've found my best option under the circumstances is to trust what the scopes displays (waveform, vector scope, histogram) in the color correction module of the NLE are telling me, not the colors my eyes are seeing.

I also sometimes burn a disk to play on the HDTV in the living room. If you don't want to get (or can't afford it right now) the right hardware to display to a proper monitor, then trust the scopes, not your eyes.

And of course the gamma shift in Quicktime that occurs because of the two color spaces is a real pain, having to encode twice for 709 viewing on tv and RGB for the web. But you have to do what's necessary to make the footage look right.

[Bruce Watson]

Originally Posted by Will Thompson

I want the best possible setup for accurate color reproduction when editing video (and ideally photos as well).

There are only a couple of options if you want an all-in-one solution. Eizo makes a few monitors that can display in both Rec.709 (HD video) and other color spaces such as AdobeRGB (stills). HP used to make a monitor that would do that as well, I think it was a DreamColor, but IDK if it's still on the market. Neither the HP nor the Eizos give you any real-time tools like waveform monitors or vectorscopes IIRC. So all you get is the image itself.

Other than that, if you want WYSIWYG video editing (and you can't do accurate color grading without it, or at least I can't), you need a monitor that can display Rec.709. There are tons of these, search for "production monitors". Or, HDTVs of course, but if you go the TV route, be sure to get one that can be accurately calibrated (some have ISFccc calibration mode which makes it easier and more accurate).

There are a number of reasons to use a good production monitor. One is that it's big enough that you can actually see the video so you can do a better job of evaluating it. A small image that takes up maybe 1/4 or 1/3 of your screen (what many NLEs will give without constant playing with the interface) is a lot harder to judge than an image that takes up all the real estate on a 24" monitor. And a good production monitor will give you real-time tools like waveform monitors, RGB parades, vector scopes, etc. Most NLEs provide these tools, but they don't run while the image runs; the tools only update when you stop the image. While useful, not nearly so useful as real-time tools.

[Ivan Castell]

Sorry for resurrecting and old thread. I've got the same open questions for color accuracy on Premiere CS6/FCPX/Avid, and Apple Color/Speedgrade without an I/O card.

I know the best way it's to get a proper I/O that convert computer signal to video signal and send it to the monitor, but in my case I have an imac with only a displayport (no thunderbolt), so the only way of attaching a I/O card is by using an old MXO and it's unsupported on FCPX, Premiere and new NLEs.

I'm thinking of buying an HP Dreamcolor (that can work in HD 709 color space) and connect it directly with a displayport cable. Like most people on this thread I've read the provideo coalition post, and if CS6 can really do an accurate YUV to RGB conversion, then I don't see the need for an I/O (for me). I just want an accurate broadcast preview. Does anyone know if this it's true?

Even a tech from the HP department said that there's no need for an I/O card using the dreamcolor attached via DP or HDMI, if you're sending a true RGB signal.

FCP doesn't do a proper conversion for the full screen preview, FCPX I don't know (I don't use it), Apple Color afaik it's not capable without an I/O card, same thing for Resolve, but I wonder if Avid does it right, and Speedgrade or AE (as part of CS6) will do it right.

[Sareesh Sudhakaran]

Originally Posted by Ivan Castell

FCP doesn't do a proper conversion for the full screen preview, FCPX I don't know (I don't use it), Apple Color afaik it's not capable without an I/O card, same thing for Resolve...

Interesting Ivan, can you point to a resource where this has been proved?

[Josh Bass]

So here's something, I was talking to a friend of mine who's a professional colorist, and he said the Ipad (that includes version 1), out of the box (i.e. no tweaking with apps, if that's even possible) is actually 99% REC 709 calibrated, and finds it true and accurate to his much more expensive monitors.

I'm likely getting an Ipad mini soon, and was wondering if anyone knows if, aside from the non-retina display and lower resolution (mini is 1024x768), they are basically the same as far as gamma/colors/etc.?

[Ivan Castell]

Originally Posted by Sareesh Sudhakaran

Interesting Ivan, can you point to a resource where this has been proved?

I get this information reading other forums & tech blogs, so maybe it's right, maybe not, I don't really know for sure. I wish it had been proved, and have reliable information so we don't have to speculate :)

- FCP: Anybody seems to agree that Digital Cinema Desktop preview without an I/O Card it's not accurate for CC. Even Apple said it on 2005. (Pro Video Coalition: TecnoTur by Allan Tépper)

Although Apple's colorspace conversions are certainly proper and trustworthy when rendered via software, Apple's 2005 warning indicates that this is not the case with the realtime conversion done with the Digital Cinema Desktop feature. To my knowledge, this has not changed with any newer version of FCP, and if it has, no one from Apple seems to be flaunting it.

- Apple Color: Apparently the preview window can't be trusted as accurate. And you need a I/O card to send a trusted signal to the monitor. (Pro Video Coalition: TecnoTur by Allan Tépper)

Although Apple's Color program handles all material exclusively in RGB, to my knowledge, the program still does not pipe its program output specifically or accurately to a graphic card output, but only to one of the professional i/o devices.

Also here:
Color Grading is done on a proper monitor | Biscardi Creative Blog

- Resolve: I don't know, I don't use it. I remember reading on reduser forums that the GPU card can't be trusted, but I don't have the source.

- FCPX: Don't know. I don't use it.

- Premiere CS6: Apparently the YUV to RGB Conversion is accurate:
Adobe Community: How does P Pro handle YUV (YCbCr) and RGB color spaces?

[Josh Bass]

But doesn't AJA have a $200 i/o box, if you have a thunderbolt Mac? So not really a huge additional investment at this point, is it?

[Ivan Castell]

Originally Posted by Josh Bass

But doesn't AJA have a i/o box, if you have a thunderbolt Mac? So not really a huge additional investment at this point, is it?

No, I have a mini displayport Imac (late 2009), no thunderbolt. I wish I had one, because there's plenty of low-priced options for this interface :)

[Ivan Castell]

Originally Posted by Josh Bass

So here's something, I was talking to a friend of mine who's a professional colorist, and he said the Ipad (that includes version 1), out of the box (i.e. no tweaking with apps, if that's even possible) is actually 99% REC 709 calibrated, and finds it true and accurate to his much more expensive monitors.

I don't have an ipad but that's very interesting. How do you connect it to get the preview? Or do you play the final output from a file directly in the ipad?

[Josh Bass]

Yeah, bummer 'bout the mac. One of several reasons I just bought a mid 2011 :-). I think your options are limited to the $1000 Matrox something or other? Unless someone finally creates a backwards compatible thunderbolt adatper.

Re: Ipad. . .unfortunately not a perfect solution. Basically, I think you have to export a movie (this colorist friend recommends uncompressed 8 bit or 10 bit, depending on your original format, rather than Prores or anything else, to prevent color/gamma shift) and load it to the ipad and play it off there.

He also mentioned a pretty neat method where you take a color chart, import into your NLE/CC software, throw it up on your scopes, and apply a CC filter to it and tweak 'til the scopes say the chart is bang on (i.e. red is red, black is black, white is white, etc.) Then, you look at your monitor. Is your white a little on the greenish side (etc. etc.)? That's how inaccurate your monitor is. Now you eyeball and tweak your monitor to get the color chart to look right (if the whites are little green make 'em white, etc.). Obviously not 100%, not a scientific method, but better than flying blind and will probably get all of us who aren't doing high end commercial/broadcast/theatrical release work, "close enough".