Color (or colour) correction in Kdenlive - how to use Reference Chart and Vectorscope (and other tools eg. colorchecker)

Hi!

For the last time to improve my videos I used a grey card and later ColorRight:
1) http://www.youtube.com/watch?v=U1KqIljDR5o
2) http://www.youtube.com/watch?v=gV_c-HQhvIQ

Few days ago I have found this video (English subtitels) about color reference chart:
http://www.youtube.com/watch?v=43akIuQf_iw
something like grey card above, but with more options. From 2m35s in this film you can see use of it with video editing software and Vectorscope. Is someone using Vectorscope in kdenlive and can explaine some more how to calibrate video in kdenlive to such Reference Chart? As we can see from 4:00 the results of proper use those tools are huge.

http://userbase.kde.org/Kdenlive/Manual/View_Menu/Vectorscope

And the links to Granjow's blog on that page might help somewhat.

But maybe you are the man to figure out how to do it and write the manual !!!

Thanks for the links (I knew only about one of those).

I hope Grajnow will tell us some more about how to use Vectorscope with Reference Chart. Anyway, as soon I have found something and I will know more, I will do a small You Tube manual.

What is your experience in color correction ttguy?

For me 'White Balance' (from Effect List -> Coluor correction) works pretty well, I use a grey card and the result are impressive.
But I am not happy at all with '3 point balance'. When I use a 3 colour card (grey, white, black), after picking up of those 3 colours into effect, the results are really bad. The picture looks unnatural and overexposed. Any idea what I am doing wrong?

If shooting to a gamma encoded 8bit video or image format then white balance really needs to be 'right' in camera so the color adjust whatnot or any white card or 18% grey card and adjust WB in camera. Then shoot. Its too late really adjusting non decently white balanced 8bit video or images after especially with low precision 8bit adjustments like kdenlive has currently, when MOVIT coded filters in MLT is exposed in kdenlive then more precision but still on 8bit gamna encoded source.

If shooting raw image ie: 12bit unprocessed then no white balance or gamma has been baked in so shooting a test frame with color adjust or grey card in the scene helps set WB on raw data in the raw development process.

Interesting read is Shane Hurlbuts suggestions about WB on his blog.

http://www.hurlbutvisuals.com/blog/2013/02/using-color-temp-hd-video/

And also Kevin Wang on Flickr with his Canon picture styles strongly suggesting achieving the look you're after by adjusting color temp in combination with certain picture styles.

http://www.flickr.com/photos/aeronation/collections/72157625101919874/
If you need to reproduce the color of a logo or some memory color then WB before shooting will probably get you closer to that color with minimal grading.

If you have the color chart shown in your third video, AND if the six colors on the right side of the chart correspond to the six basic colors (hues) in a video color bar test signal of the same standard that your camera is using (rec 601 or 709), THEN the ANGLES of the blobs in the vectorscope should be the same as the angles of the color markers on the vectorscope. The radii will probably be smaller, as the colors on the chart do not seem to me as saturated as the color bar signal.

Best zoom in on your card, so that the part with the six colors fills the screen, otherwise you will get more blobs on the vectorscope, making it confusing.

For a simple white balance, the white and gray fields on the back of the chart, should both make a blob in the center of the vectorscope.

Use the vectorscope from View/Vectorscope, because the one under Effect list/Misc/Vectorscope is not correct: it uses graticule from an analog NTSC vectorscope, but equations from digital video. (I plan to fix that, sooner or later :-)

P.S. ColorRight: hahaha 20 years ago cameras had white translucent lens covers that were used this way. In fact, with such a device, you should do the reference shot from the model towards the light (as with an incident light meter), not the way shown in the video.

Thx for a both answers.

Marko, how to check which (rec 601 or 709) use my camera (Nikon D5100)? Any ffmpeg command? I have read that eg. most Cannons (apart 5D MK3) use 601 for their HD video.

I have found not all color charts can help, only those for video - a very good article explaining this (with lots of vectorscope charts) - a comparationa 2 popular cards, one for photo and one design directly for videographers (ITU-709):

What Good is a Macbeth/Colorchecker Chart?
http://provideocoalition.com/aadams/story/what-good-is-a-macbeth-colorch...

Some desription from producer SMPTE OneShot™ Pocket chart:
The Color Rows
The ITU-709 high definition broadcast standard defines three standard primary colors--red, green and
blue--out of which are created three standard secondary colors--cyan, magenta and yellow. These
hues are reproduced on the OneShot chart and, when properly white balanced in a grading session,
these colors should line up with the red, green, blue, cyan, magenta and yellow target boxes on a
standard ITU-709 vectorscope.

> P.S. ColorRight: hahaha
I very happy with this tool. Its much easier than with a grey card to make a photo to a custom white balance, especially when you are in hurry (eg. events). Skin tones look pretty and you can see small test similair to ColorRight - Expodisc an grey card.

White Balance Tool Comparison in Digital photography
http://www.youtube.com/watch?v=XWVkC4D5Lcc

vylaern, the reference to BT.601 with Nikon and Canon DSLR's is with regard to the luma coefficients used not to be confused with color primaries. Regardless of luma coeffs Nikon and Canon use BT.709 primaries and getting the luma coeffs correct really only affects conversions to RGB, for such things as playback and RGB based scopes like RGB Parade & Histogram.

RGB is the primary color space from which all others are derived, both in theoretical colorimetry and in practical hardware (sensors have RGB filters).

601 and 709 are based on different RGB primaries, and the different luma/chroma coefficients are a just consequence of that.

Because the difference between 601 and 709 is mainly in the green primary, the luma coeffs are affected the most.

So, if your chart is 709 and your camera 601, green (and cyan and yellow) will be a bit off. If I remember right, the differnce is mostly in the saturation of the green primary, so its angle may not be significantly off.

As your link says, the angles are important, because the white/grey value is insensitive to rotations, it will only show shifts.

> P.S. ColorRight: hahaha
By laughing, I did not mean to say it is an inferior tool, I just laughed at the marketing, which is trying to sell a "new" idea.

Canon & Nikon DSLR's for which vylaern is discussing encode HD video using JFIF specification, http://www.ecma-international.org/publications/files/ECMA-TR/TR-098.pdf

But BT709 primaries and BT601 luma coeffs, its in the metadata within the format, ffprobe, mediainfo, QT clearly state.

BT.601 is color primary agnostic, primaries are based on lines of resolution, so could be EBU or SMPTE and therefore regarding 720P and 1080P BT.709 primaries.

Chroma is normalized over full 8bit range, +-128, luma over full 8bit range, the h264 video stream is flagged with a h264 VUI Option 'fullrange' to signal to the decompressing codec to scale levels into restricted range before conversion to RGB. It's a bastard format :-)

I am waiting for DSC Labs The OneShot as SMPTE Pocket OneShot is NOT aviable in the UK yet, so I will make a short movie with the card to download, so everybody could try to play with Vectorscope, so we could check the results and we could see if is worth.

Hi again,

Thanks to this article:
http://provideocoalition.com/aadams/story/what-good-is-a-macbeth-colorch...
(What Good is a Macbeth/Colorchecker Chart?)

I have found 2 others articles about color corrections, vectorscope and color charts:
[1] CAMERAS: Rough Guide to Color Grading with the new DSC Labs OneShot
http://provideocoalition.com/aadams/story/cameras_rough_guide_to_color_g...

[2] CAMERAS: A New Chart for Film-Style Production—The DSC OneShot
http://provideocoalition.com/aadams/story/cameras_a_new_chart_for_film-s...

In this [2]^^ above there is even a link to the Granjow's article on this website (kdenlive.org)
Vectorscope: What the I and the Q lines are good for
http://www.kdenlive.org/users/granjow/vectorscope-what-i-and-q-lines-are...
Kdenlive Team rules!

For the moment, I would like to concentrate on the article from [1]^^ link and translate it step by step from Apples's software into Kdenlive.

(1.) This screen, botton-right:
http://provideocoalition.com/images/uploads/OSC_Before_Primary_Close.jpg
Is this the same like kdenlive like RGB PARADE or maybe WAVEFORM from view menu?

(2a.) Author says: 'The first thing I'm going to do is zoom in to the chart so it fills the entire frame.'
so from this:
http://provideocoalition.com/images/uploads/OSC_Before_Primary_Wide.jpg
to this:
http://provideocoalition.com/images/uploads/OSC_Before_Primary_Close.jpg
Is there any tool in KDENLIVE which can zoom the picture in the Project Monitor, so I can do this like above?

(2b.) Is there a such tool like in this film, where in about (1.00m), you can hide rest of the picture (crop function) or (garbage matte?) in other software, to concentrate on the color in vectroscope:
http://youtu.be/jSlJXq82veY

(3.) Author says about 40 IRE or 100 IRE so in kdenlive is the same 0-255 scale in eg. RGB PARADE or WAVEFORM?

(4.) What is a tool in KDENLIVE similair to do this job from an article:
http://provideocoalition.com/images/uploads/OSC_After_Primary_Close_cont...

(5.) Author says: 'I've zoomed in on the vectorscope by 2x (or 25% in Color's terminology)'
If eg. 2x is 25% in Color's terminology, what is 3x or 1.5x (kdenlive scale)?

I will ask some more questions later...
:)

1. RGB Parade, not luma waveform, two different color models.

2a. Undock it, freely resize it and move to a second monitor.

2b. ?

3. IRE is an analog concept. 100 IRE is equivilent to 235 YUV (analog), digital value 235 YCC and 255 in RGB. Waveforms vary, some show upto 100% on the graticule as 100 IRE others as 100% RGB or 100% YCC. Kdenlives waveform appears to showing RGB values and slightly incorrect in the low end, a value of 16 in a test file I use is appearing as 28 on the waveform, so the YCC to RGB calculation seems wrong. A YCC Luma waveform should show upto 120%. http://www.kenstone.net/fcp_homepage/video_levels_nattress.html

4. SOP/SAT effect.

5.?

So I am reading this thread in awe of the details on display.
As a newbie to colour correction is it true to say that a basic use of the stuff being described here be ...
1.Take video of your test card (be it White, grey, multi coloured) under the lighting conditions present.
2. Do the same thing for your next scene (under different light)
3. Get both lots of footage into kdenlive and view the test card footage with a colour scope and note the slope and location of the graph in footage A and then apply colour correction effects on footage B until the graph in the scope on that footage matchs that for footage A

> yellow:
> 2a. Undock it, freely resize it and move to a second monitor.
> 2b. ?

2a)
I mean not to resize the window, because inside the window is the same picture, so if I resize the window the picture inside is still the same (smaler or larger) :)
I would like to resize picture inside the window, from this one, where we have a photo of a chart + table + teddy toy (top-right window):
http://provideocoalition.com/images/uploads/OSC_Before_Primary_Wide.jpg
into a window with only a chart (without table and teddy toy)
http://provideocoalition.com/images/uploads/OSC_Before_Primary_Close.jpg

So how you can see the wectroscope and rgb parade and others show different results in those both examples (for the same photo, but different parts of this photo).

2b)
The same story in this link (video):
http://youtu.be/jSlJXq82veY
Olivia says (and shows) RGB parade of whole picture (1m10) is DIFFERENT than just grey part of this (the same) picture (1m10 till 1m25), so is possible to make a propper corretion.

I mean, if in KDENLIVE I cannot crop from the all picture(chart + table + teddy toy) a part with just a grey scale or color chart, so will do a full-frame shot of this chart , but I hope it is possible by software like in 2 examples above.

> Ttguy
I was using in my last video just a grey card (as usually) but I wasn't happy with the results (difficult lighting). As the author of those articles above says: "You can't trust gray scales alone in video," I told them. "You MUST see color to know what the camera is doing."

In Grajnow's kdenlive blog article (Vectorscope: What the I and the Q lines are good for) there is an interesting link to this article:
http://prolost.com/blog/2008/3/23/save-our-skins.html
In this article thre is a link of a photo, where a white balance looks OK:
http://rebelsguide.com/dl/hulk_01_rainSample.jpg
Pushing it to a pervasively blue look yields this result:
http://rebelsguide.com/dl/cool.jpg
And thanks to the I/Q lines from vectorscope, we can use a blue look but keep the skin color :)
http://rebelsguide.com/dl/cool+skin.jpg

So this is a reason, vectorscope and eg. RGB parade is so a fantastic tool (many thanks to kdenlive team) soe I am interested to use it (not only a grey card).

:)

2a. My apologies, I thought you wanted to zoom in on the RGB parade, make it larger.

So what about adding a video track as a mask using a shape or roto and inverting if necessary so the shape remains alpha so your chart shows and all around is black? Only problem, be careful with affine or composite if you have to use them as they can skew the image colors, I made a bug report a while ago.

Try "crop, scale and position" to zoom in on the chart.
However, I find it's UI (parameters) a bit clumsy, the scaling works from the edge (not the center) and shifts are called "tilt", and for big enlargements the shifts are not enough to bring any part in the center etc.

I tried pan&zoom too, but the scopes somehow don't change?? ***

For new shots, try to zoom in on the chart already with the camera.

Having the chart fill the frame, it is easier to identify the parts of the chart on the scopes.

Concerning point [5] above, it seems that the vectorscope, which the author used, has a "zoom in" option, this would be equivalent to chroma gain, or increased saturation.
On the Kdenlive vectorscope, you can do this using the slider on the right side.

*** playing with it some more, I found that the scopes (RGB parade and vectorscope) often do not react to the applied effects (like RGB adjust or SOPSAT), although I can see the colors change in the project monitor.
Switching to clip monitor and back seems to help...

This was with a script compile from 20130206
Compiled a new one today (20130225) Now the scopes are more responsive, but they seem to show the same signal in all three channels, R=G=B in the parade, and the vectorscope always shows a symmetric "mercedes star".

The channels on the scopes seem OK on the 20130206 version, but as I wrote above, they aren't always updated after the addition of an effect.

Disclaimer: I am compiling this on an old, heavily patched Opensuse system... although I changed nothing on the system between the two compilings above.

Many thanks yellow and Marko!

yellow - I was trying both effect but I could not manage to change anything :(

Marko - Crop, Scale and Position did the job! This is enough form me at this step :)
I had the same problem like you said in *** in your post but switching to clip monitor and back help to me as well.

So I am playing with a new skills and will ask some more question Tomorrow, on my way to go from this:
http://provideocoalition.com/images/uploads/OSC_Before.jpg
to this
http://provideocoalition.com/images/uploads/OSC_After.jpg
but not with Apple software but with KDENLIVE!

:))))

hi, the edge crop effect under crop & transform works fine for zooming in on the chart. You can control left, right, top & bottom, tick the use project resolution and you get zoom with those images.

Then the 3 point balance effect will let you sample, white, black and 18% grey for primary correction.

Thanks yellow,

Edge Crops also works pretty well :)

:) :) :)

For manual correction, as in the first link (what good is....):

The signal in a channel is a product of incident light and object reflectivity. So, if the cast is the result of unbalanced light, the right thing for correcting this would be to change channel gains (the diagonal elements in the linear color transform matrix).

To do this you can either use RGB adjust, and set the mode to "multiply", or use the slope parameters in SOPSAT.

NOTE: the above is strictly true in a linear system. But a multiplication by a constant is still a multiplication with a (different) constant after applying a pure power curve, like gamma - so the above is true in a (purely) gamma corrected system too.
Now, the 709 "gamma" curve is not strictly a power curve, it has a linear section near black, to avoid excessive noise amplification. But the difference is probably small enough to not cause problems here.
Video cameras might use additional non-power curves to manage dynamic range, in that case you might be forced to adjust lows mids and highs separately, or apply appropriate curves.

P.S. apropos the first link, "what good is a macbeth color checker"...
The author works for a competing firm, so obviously he has to conclude that it's worthless :-)
Admittedly, the colors on the checker do not correspond to the markings on a vectorscope, making them less useful when using one.
But still, since the colors are specified (the link contains a link to a pdf file with the numbers), you could use them for a check, or to achieve consistency across shots. In Kdenlive, you can use the Pr0be (under misc) to read out the values. Note that in the table, the RGB values are for sRGB, which, if I remember right, corresponds to rec 601 primaries (not sure about gamma). So if you are using 709, you should transform the table.

re sRGB, BT Rec709 primaries and transfer.

BT601 has no defined primaries of its own, its agnostic and dependant on lines of resolution whether that be SMPTE, EBU or Rec BT709.

Vylaren, doing these Primary corrections is good to know but really if time allows it would be better to do white balance adjustment in camera before shooting video or jpgs. Not so much a concern for raw as no WB is baked in then.

Secondary 'corrections' ie grading is something else.

Hello again!

My test with kdenlive, vectorscope and color chart, shows the project looks better now.

Now I am here (the second part of the article):
http://provideocoalition.com/aadams/story/cameras_rough_guide_to_color_g...
when vectoreoscope lookticle)s close to the optimum, but not close enough.

My next question is, if there is a tool in kdenlive similair like Apple's this tool:
http://provideocoalition.com/images/uploads/OSC_Sat_Curve.jpg
so author of the article could move from here:
http://provideocoalition.com/images/uploads/OSC_Hue_Curve_VS.jpg
to here:
http://provideocoalition.com/images/uploads/OSC_Sat_Curve_VS.jpg

I am thinking about rather about Mg,Cy,Yl colors as for RGB thre is lots of tools in kdenlive.

The same tool:
http://rebelsguide.com/dl/sat.jpg
was used in this article - Save Our Skins:
http://prolost.com/blog/2008/3/23/save-our-skins.html

So I could easily boost just Cyan color:
http://provideocoalition.com/images/uploads/OSC_Hue_Curve_VS.jpg
Many thanks for all the answers so far.

The tool you mention seems to be a "hue dependent saturation adjustment"

It could be probably done with the new "Region" feature introduced in Kdenlive 094:

http://www.kdenlive.org/users/j-b-m/kdenlive-094-released#comment-20471

which should allow selective application of an effect, exactly what is needed for secondary color corrections.

The procedure would be: (but I could not get it working yet...)

1. use the color selection effect (under alpha manipulation), set selection subspace to HCI, and set delta G/B/Chroma and delta B/I/I to maximum (this way, your selection will only depend on hue). Then choose a hue you want to affect, and adjust delta R/A/Hue to set the range of hues that you want to affect. Increase Slope if you want a softer selection.

2. Add the Saturation effect (under Colour). Open it's effect menu (The "=" symbol left of the "X" delete effect in the upper right corner) and select "create region". ** Now here the problem arises - I could not find a way to use the clip's own alpha, I guess this will be added later?

3. Adjust the saturation - only the hues selected in step 1 should be affected.

==========================================================

In the mean time, you can work as described here:

http://www.kdenlive.org/forum/secondary-colour-correction#comment-19420

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