Proper LCD calibration for video colorgrading
 

I need advice on the right way to set my color temperature on the edit suite monitors.

I bought myself a X-Rite i1Display2 calibration tool to finally set my monitors straight.

After running the calibration, Gamma and contrast look fine, but the grayscale tones dont look neutral gray anymore. White is white, black is black but the grays have a red tint to them no matter how I set the whitepoint.

I read somewhere that the standard for videoediting calibration is 6500K?. But that looks very red in my eyes.

Ive done some testing to show that the grays are indeed consistent now and are holding at 6500K throughout the scale, even if they have the red tint to them.

Without calibration the color temp ramped up linear to the grayscales brightness. The bright graytones went from 6500K and down to the dark graytones which ended at 9600K (maybe its just me but that looked kinda more "neutral" that way).

Furthermore Im concerned with the fact that nearly all home displays, laptops in particular seem to follow the same pattern.. (bright grays have a lower Kelvin value than the dark grays). And since I mostly make videos for web viewing, my correctly calibrated material will end up bluish on the avarage screen.

Any thoughts?

I would like replys for both those who do videoediting for TV and for web. Are there any differences?

I can see that professionally graded movies look great on any screen. Calibrated or not. So I guess the question is, whats the trick? How do they maintain the color to be nearly the same on all consumer screens?

Im gonna post a link to a music video Ive done.

http://www.youtube.com/watch?v=T16umXG5lOU

The piece was graded before I got the calibration tool. In my edit bay it looked ok, but now after calibrating my monitors it looks to orange, dark and a bit over saturated... At the same time, when ever I see it on some of my friends laptops, it looks very pale, dull, and to bright.

Now look at this little piece of geniuality at work.

http://www.youtube.com/watch?v=auF9ONmSUlQ

I'd eat my leg to figure out how they graded it to be so consistent.
It looks fantastic on every monitor Ive seen without to much noticable difference.

This seems to be a topic that keeps coming up. The belief that color timing a monitor can be done with a hardware spectrometer is urban legend, plain and simple. The fact is that spectrophotometers, e.g. Spyder, Gretag macbeth, etc., are designed to balance screen displays for PRINTING photographs. The color maps these devices generate are designed to represent, on screen, injet printer colors.

The best procedure for color timing a monitor is to go thru the process here:
HD CINEMA: HD MONITOR CALIBRATION (aka how to calibrate w/ ARIB bars)

If you don't do inkjet printing of photographs, throw that Spyder away, or at least put it in a drawer somewhere where you're not tempted to use it.

so you are saying that Im better of with simply using a sRGB or AdobeRGB profile, which variates the color temperature of the grayscale on my screens?

That actually makes me happy if confirmed, however I still don't come closer to the answer how professional graders keep the colors in place. I know the main reason to that must be EXPERIENCE, but there has to be something in there system which helps them on the way, if its not a well calibrated monitor then what?

Take a look at the FSI monitors. Pricey. But supposed to be very accurate.

Comes in two grades but I suspect that Grade 2 would still be miles ahead of what most of us currently use.

Calibration equipment available for these monitors.

Flanders Scientific, Inc. - Top Quality Broadcast & Post Production Equipment.

Nik,

Bill's pretty much right. Many people, including myself, have gone down this same path of trying to "cal" our computer monitors for best video only to be left wonder why it doesn't look like it should.

There are many problems but the most basic one is that computer LCDs don't use the same color primaries (sRGB, etc) that video LCDs do (REC709). And for the most part the primaries can not be adjusted enough to get lined up correctly. The new HP dreamcolor might be an exception here.

Bill is almost correct that sypders, et. al. are designed for print. Actually, it is the software that drives them that is designed for print. A sypder, et. al. are just color photometers and with the right software can be made to provide fairly decent results for cal'ing a TV. Google "HCFR".

The "right way" is to get a broadcast monitor. The poor mans way is to use a HDTV and cal with a spyder.

Good luck,

Mark

Mark...

wow, this HDCR software is awesome. Problem is, I can't figure out how to use it properly. The help file is translated from French, so, it's a bit obtuse. Can you recommend any more comprehensive hekp file?

From my experience, having a broadcast monitor (LCD or CRT) is the most important fact when correcting for television. A computer LCD just does not display video in the same fashion.

This myth that the television makers have portrayed that HDTVs are interchangeable with computer monitors is just wrong.

One thing I have noticed is that I am getting a difference in gamma with HD material. When I produce something for DVD or Blu-ray I have to bump-up the gamma for internet viewing as the image will look a bit underexposed when I put it on the web.

My Editing screen is calibrated (with bars) and it looks great on my plasma.

I have not found the trick yet of one file for all sources.

I see.. So I should rather use my HDMI cable instead of the DVI? I have one of those hybrid samsung screens, that both has tv/video (HDMI/composite) connectors and computer (DVI/D-Sub)

Infact I have been puzzeled about the REC 709 thing during the last project I did, when I realized that Premiere Pro shows the image in REC 601 no matter if its SD or HD. But the single most annoying thing is the final render which looks very different on every other screen I watch it on. On some its way over saturated and crushed, on others its almost colorless and milky. I don't see that huge difference when watching other peoples work (such as hollywood movies).

One aditional question I have is, if its possible to tweak the gamut to stay fixed at 16-235.

When I use the MP4 H264 decoder from k-Lite. You can set it to playback with either 0-255 or 16-235 (standard is 0-255) but other H264 decoders have 16-235 as a standard (youtube uses one of them).

I would assume that if I set the output levels to 16-235 values in my NLE. The decoder should render the same black and while levels, in both standards. However thats not the case. 16-235 is always more contrasty. Can that be fixed?

Nik, Using a computer video card to drive a LCD (TV or dislpay) is bound to give you grief when it comes to color.

What you really need is a Blackmagic, Aja, or Matrox type of interface to drive a broadcast monitor or HDTV. There's the whole RGB -> YUV and 0-255 vs 16-235 thing that these boxes should be able to handle. There is plenty of good threads here to search thru on this subject. I'd start with the calibration thread:

http://www.dvinfo.net/conf/sdtv-hdtv...-monitors.html

Bill, I've recently moved and can't seem to find the how-to I use... and I don't have the time to write up my own at the moment. But I know that avsforum is where I got it. It's a pain to search thru but lots of good info.

Mark

Nik, Mark touched upon another important factor.

You need a pro video - video card. With proper output signals for a broadcast monitor.

Without this type of card, your video output will not be true for precise color correction.

It is not cheap to get it right!

Thanks mark... yet more money to spend sheesh...

But my question regarding the 0-255 vs 16-235 issue, was not meant as to how I can display one or the other during my edit, but rather, how do I make sure that all decoders (client players) show the same values.

To make it more clear... Would it be possible to set the levels -in the editbay- in such way so that a decoder (client player) which is default to 0-255, shows the same black and white levels as if it was 16-235? My understanding in this area is limited, but my logic dictates that if there is no information below 16 and above 235, then there should be no visible difference. If 16 is black, then why does it become gray when 0-255 gamut is set (in the decoder).
I just want to streamline my project to look more equal, no matter who and how people are viewing it.

On the other hand I can see that every single videofile (even feature films) that decodes with FFshow, does show a visible difference in the values when shifting between. 0-255 and 16-235. So I guess it's due to some kind of mechanic in that decoder which is "lifting" the black value above 0... thats annoying.

Hmmm... I'm not smart enough to answer your question. Let's hope someone chimes in that is.

I know what you mean though... you've got four possible out comes if you mix and match 0-255 and 16-236 encode and decode. I guess you should pick that which matches the majority of you're viewers. In other words: 0-255 for web and 16-325 for DVD and or broadcast.... possible BR, but I'm not there yet.

Mark

What exactly am I looking for in a blackmagic card? Which one would you recommend? Intensity? HDLink? DVI extender? Do those contain the means to give me the right image? What "spec/function" makes the difference that a Nvidia card dosn't have? Thanks

The difference between these cards and a Nvidia or ATI card is that they are designed to output video to match video standards; ie: 1080i/p, 720p, 480i/p, ntsc/pal, using video signaling formats (usually YUV); and video color spaces (REC604, REC709, etc). While Nvidia and ATI cards are designed to output video to match computer standards, ie: 1900x1200, 1680x1050 frame sizes, etc; using computer signaling (usually RGB); and computer color spaces (sRGB, AdobeRGB, etc).

They all have the means to produce the proper signals but vary widely on features and price. I have no idea which if any of the work better (or worst) with PP. I would suggest that you research all the cards yourself... it give you a reasonably good education.

For what it's worth, I'm in the "poor man's" strata so I have a BM Intensity (the pro wasn't out yet when I got this card). I use it to drive a Samsung HDTV that I calibrate using a i1. The results are fairly good, but I know it's not perfect. And so far I haven't had color issues that you see with this setup. When I have the coinage I'd like to get a broadcast monitor, and maybe a HDLink.

thanks a bunch.. Ive been reading about BM all day, and got somewhat smarter along the ride.

As I understand it the intensity card only functions as a video feed from your NLE, so it puzzles me how you could be able to calibrate it using a i1, since it's a computer monitor calibration tool, and requires it to be stored as a ICC profile at the end.

Hi Nik,

You're not calibrating the card, you're calibrating the monitor (TV in my case). So I've got some more homework for you :-) Head over to avsforum.com and read up on calibrating HDTV's.

I use an i1 with the HCFR software on a laptop. I've generated my own test patterns in my NLE (FCP) that are output to the monitor (HDTV) via the BM Intensity. It works reasonably well. If you rather use a comercial product rather than HCFR, google "Calman". Be prepared for sticker shock... but at least the www has some very good info on it.

Bill... I'm still looking for the step-by-step process for HCFR but no luck yet. I guess I'm goinig to have to write it up myself. Can anyone loan me a spare couple of hours???

Mark

Hey Mark...

Thanx for wanting to go thru the effort. While there are many features I haven't mastered, I've figured out enough to set up my displays by using the Luma and RGB plots while adjusting my videocard RGB and gamma parameters. I've come up with some pretty nice looking displays, significantly different from the defaults.

Quite astonishing, actually.

Glad to here it Bill. What display are you using???

Mark

Mark...

Laptop : Geforce Go 7900gs with a samsung 205BW LCD
Workstation: Quadro FX1700 with two Sony LCD

Im finally convinced and placed my order for the Intensity Pro... Lets se what comes out of it.. I guess the next step will be to find a suitable monitor.

I was looking at the NEC line. The JVC broadcast monitors look very interesting to. Exept the pricetag. This one: JVC Professional Features page would be the one I would go for, IF it were available in Europe. Anyone know if it would work outside USA?

BTW take a look at this:http://pro.jvc.com/prof/attributes/f...l_id=MDL101867 that baby just got added to their product line.. OMG!!

The JVC DT-V24L1U can be had stateside for ~$1700-1800 from a number of places... not sure about EU. I've had my eye on it. Once I get back there I'll look at it more seriously. Some will pan it and tell you to go for the DT-V24L3DU for the SDI connection. That would be nice but not sure it's needed by us amateurs. While a broadcast monitor is the right way to go, if you're on a budget a good HDTV is more that passable at half the cost.

Either way, please tell us how it all works out for you. I for one am interested in how others have their systems set up.

Bill,

Found the procedure that I use. Sorry it took so long... lost link... lost paper copy. Anyway:

GREYSCALE & COLOUR CALIBRATION FOR DUMMIES

Some notes:

1) This is a "how-to for Dummies" version. On the bright side, he really includes a lot of good techincal (why do it) info. after you go thru it, you'll see why I was reluctant to write my own :-)

2) This is written for calibrating a CRT projector, but he includes enough info to handle LCDs as well.

3) The test patterns he uses are sourced via DVD or an output from HCRF. I generated my own in FCP (Motion)... it's easy enough to do if you understand what you're after. If you use FCP, I can send you the file. I haven't tried to make it into a .mov yet... I need to verify that nothing changes in the process if I do.

Good luck, if you use it, let us know how it works for you.

Mark

Very nice.. The HCRF was exactly what I needed...

Im on the PC side, so FCP is not in my domain.

Great stuff, Mark. Thanx, so much.

So I finally got my Intensity pro delivered and setup...

The image is terrible... Everything is way way oversaturated, it has a very redish feel to it, the contrast seems to high, and overall the image is dark. When I look at the Colorbars it looks wrong aswell. And the pludge is not visible in any way. Its as if it wasn't even there.. Just black in all 3 fields no matter how I tweat the monitor. If I try to raise the brightness all three fields just go gray alltogehter in the exact same tone.

Any help?

I thought that the card had some kind of managment tool software with it, to set the right color space, gamut, and levels but there is nothing as far as I can see..

Any help?

I've read a lot of bad things about that Intensity card, Dump it! Sorry for tha bad news. I'm looking forward to the releas eof the AJA IO express...it looks like something useful, esp. if it can encode to the cineform DI.

Are you serious? Damn... Well there must be a way to set it straight. I doubt that Blackmagic would make a product so bad as it looks right now.. To their defence, I tried connecting my monitor with HDMI cable but using the DVI output of my graphic card, with an DVI to HDMI adapter.. It gives similar look only worse. But the feeling is kinda the same.. To much saturation, red, and to dark. Then I connected the intensity with the monitor using component.. Exactly the same image as with HDMI...

The problem may be the monitor.

My Dell Inspiron has a display that HAS to be the worst thing I've ever had to deal with. After applying the HFCR tool that Nik recommended, for the first time in 3 years, it looks like something that's close to the second Sony monitor that i use alongside. I', WAY impressed with HFCR...thanx Nik for showing me the way. The Dell still has regions all over the screen that are different, but, at leat everything is now somewhat consistent.

Well the problem is my monitor has very limited tweak options. And none of them can stretch far enough to give the right image if used in HDMI mode. This is very bad, if the Intensity only has one setting and you cant change it.

Im not sure what it's suppose to do in the first place..

Mark!. How do you see any advantage by using your intensity? It has absolutelly nothing to offer image wise. I should have just bought a good Monitor instead and keep using DVI connection, untill someone can explain what the h... a SDI or HDMI or COMPONENT card can do that DVI based cards cant.

Nik,

You still haven't changed the fundamental problem... the monitor. The Intensity card has no color adjustments of it's own. It just outputs the color space in the proper format. You are correct that you monitor just doesn't have the proper adjustments... it a computer monitor, it was designed for sRGB. You need something designed for video. And while it's not a substitute for a broadcast monitor, most HDTVs these days have the proper adjustments to get fairly close to the REC709 standard. So if you have a decent HDTV, hook that up and then adjust using HCFR. You should notice a big difference.

Bill... I know you we thinking of me when you credited Nik for the HCFR stuff :-)

Mark

No I've been using a hybrid HD tv all the time.. It has DVI and HDMI.

Besides newer Nvidia cards have this:

Mark...


a thousand apologies for misplacing the credit. HCFR is an awesome piece of work. Thanx for turning me on to it.

-Bill

Nik, What's the make/model of your monitor???

Bill, No problem. Figure you just got lost in the thread. Anyway, It is a spiffiy little app... glad it's working for you.

Mark

Samsung Syncmaster 225MW

Nik,

Well, looking thru the manual for your monitor, if you use a TV connection (I'd go with the HDMI) it appears that you should be able to calibrate it some (pages 36 & 37). But it will be limited as it doesn't have the abilityto adjust the primaries. How familar are you with calibrating a TV??? And what is your procedure??? Are you using HCFR and a probe??? If so which probe???

Mark

I tried using the HCFR with little luck. And it feels a little complicated, especially because he is using a projector in the example. I use the EyeOne probe.

The problem is that the contast and brightness adjustments on my samsung are not enough... Even at 100% contrast the image is to dark, and hense way to "contrasty" If I ad more brightness, the blacks are gone... So, yeah the monitor might be the issue. However it puzzles me that the Intensity dosn't have adjustments to counter it.

I can ALMOST get the right picture if I use my Nvidia 260. Using HDMI Cable. Switch to Y Cb Cr and lower the contrast to 0 on the graphic card itself. Otherwise the signal is to strong. So If i plug in the Intensity instead. I basically get the same image, as I would do with my Nvidia, exept there is no way to lower the contrast.

Another matter that dosn't suit me is, that I have to use the Blackmagic profile in Premere, if I want to use it. Thats not a good workflow.. The audio goes out througt the HDMI cable, and mutes my regular audio card, which is conected to other studio equipment.

On another note, how do you measure saturation? When do you know if the saturation levels are to much or to little.. All calibrators focus on gamma and color temperature, but none of them tell you if you oversaturate.

Finally: Before I started all this I had the impression that HDMI and DVI were directly inter compatible. But thats not quite the case. I can see that with resolution and pixel shifts.. If I use HDMI, there is no option to select the native resolution of the screen, (as a additional desktop monitor) and I can see smudging on edgy pictures and chromatic abaration.

I'm wondering if the TV has some sort of dynamic contrast processing that might be screwing up your ability to adjust it. A lot of TVs have this sort of thing. However, I don't find anything listed in the manual for tuning it off or if it even has dynanic contrast... The so called "dynamic mode" should be disabled when set to custom. What are you using for your test patterns/colors??? Do you have access to a "better" TV that you could try it on??? Sorry, but I'm kind of running out of ideas.

As to the Intensity, it is purely a pipe. It's one of the things I like about it. What you see in the NLE should come out unaltered. While I've had a few issues with mine, it has not been with it's color performance. Perhaps I've been luckly. Have you contacted BM questioning them concerning this???

I'm not sure what you mean by "Blackmagic profile in Premere"??? I'm using FCP and it doesn't ring any bells with me. Also, I've never had the audio issue you state... I'm running mine thru a Saffire box via firewire with the video going to the Intensity HDMI no problem.

As for the saturation... if everything is cal'd correctly it should take care of itself. Part of the process is to set the white point level to a known intensity level. I usually do this when I'm setting the color temp as the reads are available at that time. I don't remember exactly off the top of my head, but setting this to 120 cd/m^2 sounds right to me. If I have time tonight, I'll look it up.

As far as using the HCFR procedure I linked to.... I know, sometimes you have to read between the lines. It took me several times of stepping thru it, finding little things along the way, before I was fairly confident I was getting good results. That's what you get for free.

Mark

I spent two months researching color calibration of monitors and here's what I discovered.

1) Rec 709, 601 and sRGB are the same gamut, but they use different gamma encodings.

2) Rec 709 and 601 also use different gamma encoding.

While you will here numbers like 2.2 thrown around for gamma, depending on how that's used for calibration, it may not be accurate. That's because Rec 709 and 601 do not use the gamma value by itself, it's plugged into a larger formula. And even that formula isn't used throughout the entire color range. At the deepest shadows, what's called a linear toe slope is used, so the gamma curve is actually a sloped straight line at the lower left corner and then quickly transitions to curve. This is why getting the shadows correct is so difficult, because Rec 709 and 601 each use not one gamma formulas but two.

I found the closest overall gamma correction that's closest to Rec 709 is about 1.95. It favors the shadows over the mids, but I think that's a good tradeoff.

As for Spyder, I've used it with okay results. You have a choice of what colorspace you want to calibrate to and what gamma to use. You can also tweak the response curve by placing control points on it (I never did this).

What you're saying, here, is true for camera acquisition. This is done in order to better match the camera sensor characteristics, and to help in saving shadow detail, rather than crush all the dark areas of the image. And, certainly, gamma toe and head manipulation during post production is part of the color grading that needs to be accomplished.When you get to display gammas, however, i.e., the gamma curve used by a monitor to display an image, it's somewhat misleading to think in terms of a gamma "toe". The whole point of calibrating a monitor is to display chroma and luma that is a fairly standardized representation. This allows color correction that is predictable and consistent across a multitude of display devices. The minute one imagines custom gammas for a display, we begin to step out of the standardization arena, and really should be avoided for true color grading and timing.

A very simple test of your monitor standardization can be done by moving an image between all your diaplays. Do things look the same on all of them? If not, something's not standardized. of course, the REAL test is to go to a customer display and have the coloring and "look" appear as the colorist intended. That's a wee bit more involved than getting all your monitors to look the same.

Oh well. Problem solved. I bought a new monitor, and works like a charm. Don't need the Intensity card tho, the Y Cb Cr mode of Nvidia cards is brilliant. I don't know if its accurate for rec 601/709 but seems close enough for me. I don't know how to test if your output actually delivers one or the other gamut