DrDre

I see, but that does mean that the frame with the soldier's face could not be corrected based on the Darth Vader frame. The two frames are not similar in the sense that they depict a different scenery. 

Very impressive! Can you also use this model to color correct other frames in the same scene? In other words if I give you a random frame, could you match that to the GOUT without a similar GOUT frame or do you always need a reference frame? The way I set up the model, it can in principle correct all frames based on a single frame, assuming the color degradation or color adjustments are very similar between frames. 

For example, I used the color adjustment model calibrated on frame 8228 of the GOUT to adjust another frame in the Tantive IV scene for the -1 video sample:

Before versus after:

http://screenshotcomparison.com/comparison/138468

Independent color correction vs GOUT:

http://screenshotcomparison.com/comparison/138469

This allows for the color correction of the whole film with only a limited number of reference frames.

Yes, but the sharpening will also introduce artifacts. If the print is in good enough condition, and the quality of the scanner is good enough, no sharpening should be required. 

The compression probably removed a lot of details, and the compression in these samples is truly awful, so a fair comparison can only be made if we get some uncompressed frames. 

Here's three tests of calibrating the color model on a single frame (8228), and then using this model to correct other frames for reel 1.

Calibrated on the GOUT:

http://screenshotcomparison.com/comparison/138447

http://screenshotcomparison.com/comparison/138448

http://screenshotcomparison.com/comparison/138449

Calibrated on 35 mm frame:

http://screenshotcomparison.com/comparison/138451

http://screenshotcomparison.com/comparison/138452

http://screenshotcomparison.com/comparison/138453

Compression artifacts are horrible, but it works oke, although direct matching to a reference frame will always give better results. Personally I actually like the 35 mm frame versions a bit better than the GOUT, but that's a matter of taste. Although Darth Vader in the last frame seems a bit on the green side. ;-)

Having matched the colors of Team Negative1's preservation (the video sample) to the GOUT, we can now directly compare it to SRV13:

http://screenshotcomparison.com/comparison/138443

This can also be found in the new color matching thread I created, but I guess it is also relevant here. I wrote a script for matching the colors between two sources very accurately. Since the colors of the video samples for the LPP preservation still need to be adjusted, I thought I would do a few tests. I have matched frame 8228 for the LPP preservation to four sources: GOUT, GKar, 35 mm scan from a different print, and Harmy's Despecialized Edition.

Here are the before after comparisons:

http://screenshotcomparison.com/comparison/138435

http://screenshotcomparison.com/comparison/138436

http://screenshotcomparison.com/comparison/138437

http://screenshotcomparison.com/comparison/138438

Here are the comparisons to the reference frames:

http://screenshotcomparison.com/comparison/138439

http://screenshotcomparison.com/comparison/138440

http://screenshotcomparison.com/comparison/138441

http://screenshotcomparison.com/comparison/138442

The colors match very well. However, the color corrected LPP framelooks faded. There is not much detail. In some ways the LPP scan is comparable to the GOUT and GKar. This can have three reasons I think:

1) The diference in quality is due to compression

2) The quality of the scan is not that good

3) The print itself is in pretty poor shape

Personally I think the compression is the culprit, but perhaps -1 could provide the uncompressed frame 8228 to be sure...

Now for a more interesting comparison, I matched frame 8228 for Team Negative1's video sample to four different sources: GOUT, GKar, 35 mm print, and Harmy's Despecialized Edition. 

Here are the before after comparisons:

http://screenshotcomparison.com/comparison/138435

http://screenshotcomparison.com/comparison/138436

http://screenshotcomparison.com/comparison/138437

http://screenshotcomparison.com/comparison/138438

Here are the comparisons to the reference frames:

http://screenshotcomparison.com/comparison/138439

http://screenshotcomparison.com/comparison/138440

http://screenshotcomparison.com/comparison/138441

http://screenshotcomparison.com/comparison/138442

Again the color matches very well. However, the quality of the color corrected Team Negative1 frame is not that good. There is not much detail. In some ways the LPP scan is comparable to the GOUT and GKar. This can have three reasons I think:

1) The diference in quality is due to compression

2) The quality of the scan is not that good

3) The print itself is in pretty poor shape

The color matching tool v1.2 released! Please send me a PM, if you’re interested.

Updates for v1.2 include:

An upgrade of the color matching algorithm. The stabilization parameter has been replaced by a smoothing parameter, and now is in the range from 0 to 1 (default 0.01).

Updates for v1.1 include:

The algorithm has been upgraded, such that creating a color matching model now only takes a few seconds, even for a set of 4K frames.

The color correction tool v2.2 has been dubbed the color matching tool v1.0 to distinguish it from the upcoming color balancing tool v1.0. The functionality of the color matching tool v1.0 is the same as the color correction tool v2.2.

Updates for v2.2 include:

An exported LUT should now also work in Adobe After Effects. In addition LUT creation is now faster.

Updates for v2.1 include:

1. A fast processing mode, that allows for significantly faster model building. Creating a color correction model at the default settings (using 10 color spaces) now only takes up to 2 minutes, independent of the frame resolution, while creating a single space model only takes up to 10 seconds.
2. The single color space model is now available by setting the number of color spaces to 1.

Updates for v2.0 include:

1. A new color matching algorithm, with improved stabilization.
2. An option to increase the number of color spaces, that the algorithm uses to match the source and reference (max 100). Increasing the number of color spaces leads to more accurate results, but is also slower.
3. A new stabilization parameter that has a range of 0 to 25. Use this option, if the source is noisy, or if the reference colors are inconsistent. Increasing this value improves the quality of the output image. Usually a value of 0 to 5, will lead to a much improved result, without seriously affecting the quality of the color match. Higher values may result in a slower convergence to the desired color palette, thus requiring a larger number of color spaces.

Here’s a post on thestarwarstrilogy.com:

http://www.thestarwarstrilogy.com/starwars/post/2015/12/14/Dr-Dres-Magical-Color-Matching-tool

A special thanks to thestarwarstrilogy.com for the post!

What can the tool do? It can accuratelly match the colors between a source and a reference. A color matching model can be constructed, that can then be used to correct other frames.

Here’s an example.

Team Negative1 35 mm scan of the 1997 Star Wars Special Edition:

Bluray:

Bluray matched to reference:

Other frame bluray:

Other frame bluray corrected using color matching model calibrated on the reference frame:

How does it work?

Here’s an amazing video tutorial made by originaltrilogy.com member williarob:

https://youtu.be/5OtaGT3A8Bs

When you’ve downloaded the file named ColorMatchv1_2_pkg.exe, execute the file. You will be asked to install the MATLAB runtime environment. After you have finished installing, a new executable named ColorMatchv1_2.exe will be available. Open this file as administrator, else it will not work.

A few words of advice on using the GUI. The GUI itself is pretty self explanatory.

The process is as follows:

1. Select a test image. A figure will open, showing the image. You will be able to crop the frame, with your cursor. If you don’t want to crop the frame, close the figure window to be able to continue.

2. Select a reference image. A figure will open, showing the image. You will be able to crop the frame, with your cursor. If you don’t want to crop the frame, close the figure window to be able to continue.

3. Build a color correction model. There are two processing options: fast processing mode (default), and normal processing mode. Fast processing mode is significantly faster, especially for high resolution frames, but could in theory be less accurate, although in practise this will rarely be the case. You can set the number of color spaces that will be used to build the color correction model (minimum is 1 color space, which closely mimics histogram matching, albeit far more stable, maximum is 100 color spaces). Increasing this number will lead to more accurate results, but is also slower. Depending on the resolution/size of the images after cropping and your hardware, this may take 0-1 minutes in normal processing mode, and roughly 0-30 seconds in fast processing mode, using the default settings, on an Intel Core i5. A figure will open showing you the test frame as it is being matched. With each iteration it should be closer to the reference. There is a smoothing parameter (range 0-1) that can be increased, if the source is noisy, or if the reference colors are inconsistent. Normally this could lead to unwanted artifacts in the output image. Increasing this number will prevent this, and improves the quality of the output image. Usually a value of 0.01 to 0.1, will lead to a much improved result, without affecting the quality of the color match. Higher values may result in a slower convergence, thus requiring more color spaces.

4. Save the color correction model for later (optional).

5. Import a color correction model (optional).

6. Import any number of images, and color correct them with a color correction model you just built or imported. The images will be saved in a newly created directory named “Corrected” with the same name as the original images. Color correcting a frame may take anywhere between 5 and 20 seconds, depending on the resolution/size of the frame, and of course your hardware.

7. Export a 3D LUT (lookup table) for use in other software programs, such as Davinci Resolve or Adove After Effects.

When building a color correction model you should consider the following:

1. The model assumes the test and reference images (frames) are identical, aside from the color. In other words it’s important the images are cropped in the same way (to a reasonable degree). Incorrect cropping may lead to artifacts.

2. When using a print or a low quality source as a reference, there may be color variations within the frame. For example some parts may be darker or brighter than others. If you use the full frame for building a color correction model, it will try and fail to reconcile these differences, resulting in artifacts. The best way to go, is to select a consistent part of the frame, select the same part for the reference, and then build the color correction model.

3. In theory you can match any source to a reference, but there are limitations in practise. You have to consider that a limited color depth may result in artifacts. Crushed dark colors or blownout light colors are notoriously difficult to regrade, but they also may affect the color matching in other areas of the frame. In such cases increasing the stabilization parameter should reduce artifacts, but they are sometimes unavoidable.

4. Although you could regrade an entire film, based on a single reference frame, this will probably not work in practice, because one reel may have degraded in a different way than another or one scene may have been color graded differently from another. In principle it is possible that each frame will have to be matched individually, but usually a film is graded on a scene by scene basis, so a single reference will suffice for a particular scene.

Hope you enjoy the tool. Of course if you use the tool for your projects, any acknowledgements will be appreciated. The same is true for any comments, critisism or suggestions you may have. In that case write a post in this thread or send me a PM.

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

Original start of the thread:

I decided to move the color matching discussion from the super resolution thread to a new thread. I wrote a script in MATLAB that matches the colors of the same frame between two different sources. The color correction can be transfered to other frames, although there’s of course no guarantee these will be correct.

Here’s an en example for frame 8228 of Star Wars, where I matched Harmy’s Despecialized Edition to the GOUT, GKar, and what appears to be a scan from a 35 mm print.

Here are the before after comparisons:

http://screenshotcomparison.com/comparison/138410

http://screenshotcomparison.com/comparison/138411

http://screenshotcomparison.com/comparison/138412

Here are the comparisons to the reference frames:

http://screenshotcomparison.com/comparison/138432

http://screenshotcomparison.com/comparison/138433

http://screenshotcomparison.com/comparison/138434

As you can see crushed whites, and blacks are difficult to match correctly, but the overall agreement is very good.

It says so on the Infognition website, where they explain the method with some Angelina Jolie pictures. Going from native 1920x1080 to 1440x1080 naturally involves a downscale, where you lose vertical resolution. It's not as bad as a full downscale in both directions, but still noticeable.

SR only scales by factors of two, so 720x480 to 1440x960 to 2880x1920 etc. Any other ratio is done by using a spline. I'm wondering if I can answer the question. 

@ zee944

It's just a good debate and critisism is good so keep them coming.

@ Laserdisc Master

Thanks! Missing you here buddy!

Anyway, the photos could be completely inaccurate, but this was mostly about testing the method. The reference frame I used from a different print is pretty close to the photos, as are the color corrections that are based on the reference. It may be a coincidence, but it may also indicate the photos are a reasonably good representation of the Technicolor print. I suppose Mike Verta would know the answer to that one.

Well, they were probably assuming Michael Kaminski, who atttended the screening, was right, when he said these photos are the best reference for how the film is supposed to look:

http://fd.noneinc.com/savestarwarscom/savestarwars.com/technicoloribscreening.html

Of course they are not absolutely accurate for a number of reasons, but they are said to to be in the ballpark. 

The way the color mapping works, is that you first take a test frame and a reference frame, and you match the cumulative histograms with a technique called histogram matching:

https://en.wikipedia.org/wiki/Histogram_matching

From the histogram matching you obtain a mapping between the R, G, and B colors in the test frame, and the reference frame, that can then be used to correct the colors of other frames. This should work as long as the color fading or color alterations are similar across frames. 

I used MATLAB for the color correction.

That may certainly be true. On the other hand these photos have been the basis for a large number of color correction projects on this forum. However, it would of course be better to compare directly to scans of the print. 

Sorry, I misunderstood. Could be that the photos are not actually representative of the actual print. 

It takes some getting used to, but this print is seen as being in pristine shape. It was screened at the now closed Senator Theatre a number of years back. Here are more photos from this screening:

http://photos.petergaultney.com/Movies/Star-Wars-at-The-Senator/i-LfFw9q9

In any case, I was simply trying to match the print. Whether the print has the correct colors is a matter for debate, but I think it would be a bit presumptuous to call them totally wrong, as it is one of the few prints from that era that has survived in good shape. Technicolor prints are known for their saturated colors, and their ability to retain their colors virtually unchanged for decades.

Hahaha, no insults here. My main point was to show off my single frame color mapping methodology, but it also raises some interesting points with regards to the actual colors of the film.  

Atrocious or not they are actually a pretty close match to the Technicolor IB print that is viewed as a reliable color reference, right down to the greenish color of the Death Star walls:

http://screenshotcomparison.com/comparison/138323

http://screenshotcomparison.com/comparison/138324

http://screenshotcomparison.com/comparison/138325

http://screenshotcomparison.com/comparison/138326

http://screenshotcomparison.com/comparison/138327

http://screenshotcomparison.com/comparison/138328

http://screenshotcomparison.com/comparison/138329

http://screenshotcomparison.com/comparison/138331

It would be interesting to see how such a color correction would look on a true hi-def source, but from these caps I would say it is definitely possible to do a pretty accurate color correction from a single frame. I mean the frame a used as a reference wasn't even from the same print.

Update: I noticed some of the frames in the  Technicolor IB are not exactly the same, but I guess I got my point across.

No that's not Harmy's color correction. Here's Harmy versus the corrected Harmy (when I say corrected I mean to the reference frame):

http://screenshotcomparison.com/comparison/138320

In Harmy's version the stormtroopers have a greenish color. In the corrected version they are white as snow. 

I created a color mapping model, such that I can transfer the color correction optimized to the reference frame to all the other frames. Just to clarify. These color corrections are based on a single frame, namely 8228. These are the results:

http://screenshotcomparison.com/comparison/138303

http://screenshotcomparison.com/comparison/138308

http://screenshotcomparison.com/comparison/138310

http://screenshotcomparison.com/comparison/138311

http://screenshotcomparison.com/comparison/138312

http://screenshotcomparison.com/comparison/138313

http://screenshotcomparison.com/comparison/138314

http://screenshotcomparison.com/comparison/138315

http://screenshotcomparison.com/comparison/138316

http://screenshotcomparison.com/comparison/138317

Oke, I'm going to do this in three separate posts. 

The screencap I used as a reference does closely match the Technicolor IB print. Whether the print is accurate is a matter for debate. Interestingly, if you match the same frame for Harmy's Despecialized Edition to the reference the following result is obtained:

http://screenshotcomparison.com/comparison/138301

The match is pretty much exact, and there is a surprising amount of detail visible, simply because the frame from Harmy's Despecialized Edition is in better shape than the reference frame. 

If the negatives are too degraded, I think Mike Verta's route of using 35 mm prints would be the most logical. Since they are probably in the process of converting the OT to 3D like the PT, the Reliance project is most likely based on the '97 negative. They wil need to redo/update the 2004/2011 changes, and redo the color grading. My guess is that this is being done under GL's supervision, since I can't see them altering any of the films without his blessing. 

All three films could be released in theatres in 3D for the 40th anniversary, followed by a deluxe 3D bluray boxset, that may or may not contain the originals. They might even release Legacy to test the waters next year, and then restore the other two for the 2017 bluray set, if Legacy is successful. Alternatively they might keep Legacy under wraps until 2017, and release it together with the others as bonus material. This is all speculation of course.

This is indeed just experimenting. I will definitely go for the version with the GOUT colors first. However, I was always intrigued by that frame, because it somehow has a real seventies feel to it, and the colors really stand out, unlike the GOUT. 

Just to have something to do while the video sample is being processed, I decided to have a look at some color corrections. As far as I know most color corrections are done using a Technicolor IB print for Star Wars. 

In the -1 thread I posted frame 8228 from a print that I used as a reference for some preliminary tests I did using -1 reel 1 video sample:

http://www.thestarwarstrilogy.com/image.axd?picture=/2015/06/35mm-Frame-8228.png

The question arose about the correctness of this reference frame. Having looked around a bit on the web, I came across some photos of a screening of an Technicolor IB print a few years back of the same scene (amongst others):

http://fd.noneinc.com/savestarwarscom/savestarwars.com/images/senatorcorrected/technicolor2.jpg

Aside from some over exposure of this photo of frame 8228 of the Technicolor IB print, the colors closely match the reference frame I used for the color correction. 

The question is, whether it is possible to get the same frame for the upscaled GOUT to match the reference frame. The answer is pretty closely:

http://screenshotcomparison.com/comparison/138206

When we compare the before/after frames, the difference is pretty stunning:

http://screenshotcomparison.com/comparison/138207