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MAKING A LUT HOW TO START (5 replies and 9 comments)

sashamoric
4 years ago
sashamoric 4 years ago

What is the best kind of shot to work on to make a General LUT.  Why this is confusing for me is how can you have a LUT that works for DAY, NIGHT and Tungsten.  What aspects of the image are you tweaking when you made your LUT.  Was it just Saturation, Contrast, Brightness?  Should I make a LUT from a shot that has been lit or can I just go out on an overcast day grab a quick shot of a park or something and then use that as the reference to make a general LUT. 

matthewtomlinson
4 years ago
matthewtomlinson 4 years ago

Hello,

This is Matt, the Imaging Science "Guru" James mentioned.  

The best kind of shot to work on to make a General LUT is multiple shots.  Ideally you would have an interior, exterior, day and night.  Ideally you should have skin tones to review.  If you do not have the ability to do all of that for your testing I would say having skin tones in a test is very important.  Chip Charts are extremely useful as well.  The aspects of the Lut that you will be focusing on are white point, tone map , color map.  These can and do include saturation, contrast and brightness but their manipulation does not have to be the same as what a color corrector would do.  The overall goal is to create a LUT that is solid in all situations as a starting point. So as many different images you can put through your LUT it will tell you what you should be able to expect down the line.   

Please let me know if there are any questions,

Thanks

Matt

Almax
4 years ago

Hi Matt, I shoot on RED Dragon in raw and generally use the provided REDGamma4 (in camera LUT) for lighting on set. I have found this is a little congested in the lower blacks and  I prefer to grade from the raw files later. Based on you comment above I am thinking of shooting some actors in 5600K and 3200K scenarios with an X-rite colour checker in prime view. Should I also include larger swatches of black velvet and flat white card as well? Do you endorse any brand of Chroma DuMondes/ colour checkers over others? Finally I am presuming these images are reviewed in a DI / Colour Grading suite as opposed to on a calibrated monitor. I was wondering what equipment you use for the production of the LUT in this environment.

Hans
4 years ago

Hi Matt, thanks for posting your knowledge of LUTs and grading. I was wondering about a thing that seems the final step in the grading process. Is there at some stage a multiplied solid color layer applied over the graded image? Something like: red 250, green 240, blue 220. So it seems to me. It ties the color palette together, undoing digital cleanness.

matthewtomlinson
4 years ago
matthewtomlinson 4 years ago

Hello Almax,

I have not used the xrite color checker as you described.  I can say that in testing purposes swatches of black and white are always useful to see how they react when viewed through the Lut/Color Correction  that you are using.  Unfortunately I do not have any direct recommendations for the Chroma Dumonds you mentioned.

Personally I have reviewed imagery on both projection and monitor.  

The creation of a Lut often times breaks down to a level of applying math.  I have been lucky enough that I have been able to have access to custom software to help with the creation.    There are commercial options.  First, if you are using an alexa you can customize the output Lut to a certain degree through the "knee" (K) and "Shoulder" (S).  If you have access to Nuke there are options within as well as Truelight, which a very powerful tool.

Hope that helps, let me know if there are any questions,

Thanks

Matt

rlandry1
4 years ago

Hi matt,

So all of this lut stuff is way over my head. However it is very intriguing. I'm reading it and learning things as if one would if he were to learn new words by reading a dictionary or encyclopedia. Just to humor me and/or anyone else who might be reading this section (who, like me, might be considered layman to the more sciency side of filmmaking).... please explain what you mean when you say "shoulder" or "toe" or "knee."

Thanks so much for all the indepth insight. Looking forward to reading more.

matthewtomlinson
4 years ago

Hi rlandry1,
No problem. A LUT has what I refer to as a tone map. Think of the tone map as the over all contrast and brightness of the image. To make something more contrasty you have to bend the LUT. When you bend the LUT, the LUT goes from being a straight line to being a curve. There are usually two main points where the bending on the curve occurs. One is at the high end of the curve and the other is at the low end of the curve. The high end is call the shoulder and the low end is called the knee or sometimes the toe. My understanding is that the human body metaphor is purely intensional. The shoulder and the knee are your pivot points in your curve. If you have photoshop you can emulate this by bringing in a curve editor and putting a point 25% up the curve and another point 75% up the curve and then bend the points so your curve looks like an "S".

Please let me know if that explanation is confusing.
Thanks
Matt

matthewtomlinson
4 years ago
matthewtomlinson 4 years ago

Hi Hans,

What you are describing can be achieved within the Color Correction of the DI.  If you want to have this integrated into your show Lut at the beginning of your show, that is technically possible but you always have the ability to do so in the DI.

Please let me know if I am interpreting the question properly.

Thanks

Matt

Hans
4 years ago

Hi Matt,

Thank you for your reply and sorry for my late reaction.

My question was more of a wondering if this is an ingredient of the grading in Rogers films. I like the grading very much, the contrast is beautiful, the colors. The colors all seem connected in a very subtle 'golden' glow. So individual colors do not pop out in a 'digital manner', but very natural.

Of course I respect if you don't want to reveal too much.

Thanks
Hans

matthewtomlinson
4 years ago

Hi Hans,
My apologies for not tardy response.
To be honest, it al starts with the imagery that is shot. Lighting is key. From there it is a combination of the imagery, the color correction and the LUT. The LUT is a constant. In the DI process, with the DP and the Colorist, subtle manipulation can occur. This is where the power of the DI can really come into play.

Morris
4 years ago
Morris 4 years ago

Hi Hans,

The LUTs mr. Deakins uses, are well controlled, but I think that you're giving them credit for the look that primarily lighting and lighting control provides.

Almax
4 years ago

Yes I agree I think you might need to lobby James to see if she can Mitch Paulson the digital colourist to talk about his collaboration with Roger in creating the final look.

Hans
4 years ago

Hi Morris and Almax, maybe I didn't put it well enough in my previous post. I didn't mean to say that the look is created in the DI. I know from Roger's posts that he creates the look on set and in camera. But I guess what I'm trying to find out is how much difference is there between the 'in camera' image and the 'final image'. I'm interested to see a 'before' and 'after'. On this page there are still images with a JPS watermark (what does that stand for?). They seem to miss the 'multiplied layer' that is present in the final image.
http://awardswatch.com/news/stunning-new-stills-from-unbroken-from-11-time-oscar-nominee-roger-deakins/»

matthewtomlinson
4 years ago

I would agree with Almax and Hans,
It really does start with the image that is captured and Roger is a Master of his Craft.

Ron S
4 years ago
Ron S 4 years ago

Hi,

Some of you may have seen this presentation before.  If you scroll to about 1:01:30 (a little over 1 hour into the presentation), the presenter discusses gamma curves, log, rec709, compression, lut, noise, exposure, etc.  Give it a chance.  Although he is a Sony presenter, the information is relevant.  It may be helpful for some for better understanding.  I'm not the brightest "light bulb" on the tree and I found the information easy to understand.  I had to mention something with respect to "lighting" as a courtesy to Roger, who shines the brightest.  Link below.

https://www.youtube.com/watch?v=U-HrXmRqpME»

Cheers to all,

Ron

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