Proper LCD calibration for video colorgrading

[Nik Skjoth]

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

Besides newer Nvidia cards have this:

[Bill Ravens]

Mark...


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

-Bill

[Mark Keck]

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

[Nik Skjoth]

Originally Posted by Mark Keck

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

[Mark Keck]

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

[Nik Skjoth]

Originally Posted by Mark Keck

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.

[Mark Keck]

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

[Peter Moretti]

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).

[Bill Ravens]

Originally Posted by Peter Moretti

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.

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.

[Nik Skjoth]

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

[Mark Keck]

Nik,

Glad you were able to getting it resolved, and hope you can find a good usage for the Intensity card.... hate to see you waste a few euros.

Mark

Note to self: avoid the sammy 225mw.

[Brian Tori]

Nik,

What series of NVIDIA card do you have? I am looking to upgrade and would like to have that colorspace option.

Thanks.

[Nik Skjoth]

Originally Posted by Brian Tori

Nik,

What series of NVIDIA card do you have? I am looking to upgrade and would like to have that colorspace option.

Thanks.

GTX 260. The Y Cb Cr option is only available when you connect through hdmi.

That has massive advantages over the Intensity. You can use it as a desktop monitor to watch your final renders with media player, quicktime player or what ever else you use.

You won't be able to select the native resolution with it tho.. E.g. you can see distortion in high res straight lines, like you would if you scale a picture in photoshop. But when used as a video overlay with premiere pro, it's perfect. I cant se pixel distortions when playing video files with mediaplayer either, but there might be some.

[Peter Moretti]

Kind of bringing an old thread back to life here. I've been testing out HCFR but have run into a bit of a roadblock.

I'm wondering if HCFR is capable of creating a color profile file (.icm)? This type file acts as a LUT to help calibrate the monitor. Or is HCFR a measurement only tool and adjustments are only possible via what the monitor and videocard offer?

[Dan Lukehart]

I have a question, what is the advantage/disadvantage of spending 800 bucks on a used Sony LMD-2030W from b&h and using that? its less than many computer lcd's. Do you need anything special with your computer such as cards? (im new...help me out?) Do people use these things as their main computer screen if they only edit video on their computer?

I am looking for a solution that will let me easily view correct colors when video editing and am willing to spend what is necessary, but would obviously not want to overpay. Im looking for entry level. Not perfect, but in the ballpark of correct colors.

I have a i7 PC> vegas 9> GTX275 graphics card.