GH5 GH5 to Alexa Conversion

Cary Knoop said:
With respect to the Zacuto test, I think what differentiates cameras most with respect to image quality is how well the image can be manipulated in post production without breaking down.
Click to expand...

...Sure, nothing is going to match the ARRI footage in post. But if you are in the audience watching a film shot with a mix of ARRI and GH5 cameras, you may not be able to spot which scene was shot with which camera without pausing the playback to closely examine the image for telltale flaws or advantages from each camera. ( sometimes I'll check out the tech-specs for a film on IMDB and see a long laundry list of different cameras used to make a film, yet watching the film in person I might have trouble telling which camera was used for each scene in the film )
 
Cary Knoop said:
I agree.


I certainly appreciate the work in trying to match the look of two different cameras. Certainly that is a time consuming thing to do. But it has limitations as well, unless you were to map the full color range over the full dynamic range there will have to be shortcuts. For instance matching two cameras with a single or even a few charts does obviously not address the full color space over a full dynamic range. That that is the case is already proven by the fact the author has two LUTs for different lighting conditions. Color correcting to match two cameras for a given scene is a more manageable task than trying to make an all-round matching LUT.

But I definitely see value. If you have a production with Arri cameras and GH5 cameras you might benefit from these LUTs. ACES is the alternative but you would have to tinker with the colors because the GH5 is not V-Log gamut, if you use it your colors will become too saturated. Making those changes under ACES is not easy and runs counter to the philosophy of ACES.

With respect to the Zacuto test, I think what differentiates cameras most with respect to image quality is how well the image can be manipulated in post production without breaking down. Nowadays practically every prosumer camera looks good but many quickly break down in post. For instance personally I love the GH5, I own one, but the weakness of the GH5 I find in the poor color quality of the highlights and the bad highlight roll off also the noise in the blue channel is bad.
Click to expand...
I've heard highlight roll off is better in HLG, do you find any truth to this?
 
Cary Knoop said:
unless you were to map the full color range over the full dynamic range there will have to be shortcuts. For instance matching two cameras with a single or even a few charts does obviously not address the full color space over a full dynamic range.
Click to expand...

That's exactly right. The very best $4k charts were not enough. What I did with GHa was to create my own system to measure and adjust color in 3d, through the entire dynamic range. This clocked in at about 2k samples. I've since then completely remade that system from the ground up, to accept 20k samples, and achieve a level of precision that was impossible before (while preserving affinity)

One can think of each state of camera settings as a new 'color science 3d sculpture.' Assuming a theoretical perfect optical path, aperture merely moves up and down through this sculpture. For a thought experiment, with a manual lens, the sensor knows not what aperture is doing, and aperture never shares (very secretive). White balance, on the other hand, creates an entirely new 3D sculpture as it conforms to the contours of the entire color space. Likewise a new light source, with a distinct color spectrum (which is received differently by different sensor dyes). All combines to create a single, new, static 3D sculpture


In my corner of the world, I've lost electricity for several days, and even cell tower service for a time due to an overwhelming storm. I will try to respond to inquiries as best I am able; it is a challenge to access the internet at the moment.
 
Last edited:
Sorry to say, but I don't like the GHa for now. On first sight it looks to work and it does straighten out the collors. But when I compaired it to the Mlut for VLog the colors from the GHa LUT seemed very crooked.
I white balanced the shot on booth images and just applyed the LUT in lumetri on both the same. I am going to do some more tests. The lamps used in the shot are 5200K. It does not give more DR but beats the highlights down.

Everything seems very green compaired to the Mlut.
View attachment 129840
 

Attachments

  • Mlut_vs_GHa.jpg
    Mlut_vs_GHa.jpg
    17.8 KB · Views: 0
Joost said:
LUT in lumetri
Click to expand...

The skin tone region of the original GHa is a bit shifted to yellow (incorrectly), and the Varicam LUT distinctly towards magenta.

Something critical - thanks to the tireless efforts of David L'Abbée, I recently discovered that Premiere is shifting VLog towards green, to a significant degree. This doesn't happen in DaVinci Resolve, and is a complete surprise to me. Also, the Luma curve of Lumetri shifts color incorrectly; use RGB Curves in the Obsolete folder instead (LGG wheels of Lumetri are fine)

I am working on a fix for the Premiere shift that will be part of the next larger update. There will be a Premiere set, and a set for everything else (another [PRE] may be tedious)
 
Wow, I am supprised Premiere does that. Very unfortunate. But I played around a little bit with the levels and got pleasing results imho. Especialy turning down the sat from the yellow and green a bit did good.
Start to like the LUT.
GHa_corrected_Curves.jpg
 
Is there a version for the GH5s? I'm assuming since it's a different sensor with a different colour response, it's not ideal to use this GH5 LUT for the 5s...
 
wwjd said:
Sage, any new news for us GH4 users?
Click to expand...

3dit0r said:
Is there a version for the GH5s? I'm assuming since it's a different sensor with a different colour response, it's not ideal to use this GH5 LUT for the 5s...
Click to expand...

Back when GHa was released, I had mentioned the theoretical possibility of a new system that would enable support of many more cameras, as well as achieve a level of precision that I could only dream of at the time.

That theoretical long shot has just become a reality, and support is now simply a matter of getting a hold of the camera in question. The previous window I had to measure the S has closed (the new process wasn't finalized then), so I need to find a new way to measure it at the moment
 
my video came out pretty nice with your LUT granted im horrible at color correcting but I definitely loved it! I used it on my gh5s log. Hopeing maybe you come out soon with a gh5s version but none the less came out pretty nice!
 
Dphotog said:
my video came out pretty nice with your LUT granted im horrible at color correcting but I definitely loved it! I used it on my gh5s log. Hopeing maybe you come out soon with a gh5s version but none the less came out pretty nice!
Click to expand...

That's excellent, i'm happy to hear it. The 'non-grading' approach is to expose well (middle gray around 40ire), and use 'Main'. To really optimize the image, only slight adjustments are needed, to the luma. Typically this will involve dropping the shadows and raising the midtones a bit with the lift/gamma/gain controls (it depends on the dynamic range of the scene at hand)

At the moment, I don't have access to the S, and the next update to the GH5 is consuming all of my free time (though this will directly benefit the S to a large extent)
 
You must log in or register to reply here.
Back
Top