GH5 LUT vs In-Camera Matrix

B

Bassman2003

Veteran
Hello,

I am interested in the GH5 series and have been brushing up on LOG shooting. I am seeing some great results with custom LUTs but I am a little unclear about the use of LUTs. I am a color tweaker and spend a lot of time adjusting my cameras to get accurate color. I have noticed some LUTs come with different white balances which leads me to believe that they are really post corrections of what was recorded rather than internal color adjustments or RAW shooting where you get to go back in time and adjust.

So what is the workflow regarding LUTs and different white balances? Seems like you are asking a lot of the codec to have to apply the LUT changes and bend to color correct for white balance.

Thanks for your help.
 
LUT's applied to LOG footage are indeed post corrections. The in-camera encoding process throws away information that can never be recovered. LOG profiles are NOT equivalent to RAW data.

Small corrections in white balance in post are reasonable, but a big change (like tungsten to daylight) will have easily visible color errors. The colors simply won't have been recorded or the color channel will clip.

Both white balance and exposure must be nailed in-camera for optimum results.
 
Thanks for your reply. My question or ignorance is more about the LUTs themselves. Do you need a different LUT for each white balanced color temperature? So If I have a WB of 3200k will any LUT look correct when applied or does one need a 3200k LUT to get proper results? Thanks.
 
A LUT is applied to the image output of a camera, which has already had its white pointed adapted from the scene to that of the output color space according to the camera's white balance setting. So the LUT doesn't really care which illuminant the scene was shot under. The LUT only cares that the scene was properly white balanced in the camera, or in some cases a LUT is designed to correct a certain white balance error.

Rarely would you see LUTs meant for different illuminants, e.g. one LUT for tungsten and one LUT meant for daylight. In theory making different LUTs for different illuminants can improve accuracy, but it's largely unnecessary these days as the camera does a good job of adapting the white point of the scene to the recorded color space when the white balance is set correctly in the camera. Just try to get the white balance right in the camera, or reasonably close, and then you can make whatever small corrections are necessary in post.
 
For us mortals LUTs can be very useful, but many of the better DITs, & Colorist, do not use them, preferring to roll their own looks from scratch.
 
Since I do not use higher end cinema cameras, my hope was to use LUTs to correct camera color deficiencies and improve in some areas like skin tones. Sort of like one does when adjusting the camera settings to improve the image.
 
Bassman2003 said:
Thanks for your reply. My question or ignorance is more about the LUTs themselves. Do you need a different LUT for each white balanced color temperature? So If I have a WB of 3200k will any LUT look correct when applied or does one need a 3200k LUT to get proper results? Thanks.
Click to expand...
Adobe provides DNG-based LUT's for still photography debayering of RAW files (used by ACR, Photoshop and Lightroom). These LUT's have provisions for storing two color tables (3200K and 6500K), for use with both tungsten and daylight balanced lighting. For intermediate color temperatures, Adobe's software can interpolate between these two tables.
 
Last edited:
A properly built corrective LUT (such as my Leeming LUT One series) shouldn't need more than one instance. If the camera has been properly white balanced, the LUT will be designed to adjust the sensor colorimetry to fix any inherent colour errors regardless of the light it was shot under.

Here's Sage's image (from his other post) with just my V-LogL LUT applied, to show you how a corrective LUT uses the underlying sensor colorimetry to fix the colours to be accurate, regardless of the base lighting temperature (which was tungsten as mentioned by Sage):

GHa_LL1_V-LogL_v501.png


That is different to a creative or look LUT, which is designed to work with particular input parameters to give a result. Sage's Alexa conversion LUT as shown below is such an example.

Both are valid ways of working, as long as you know what you are going for.

Cheers,

Paul :)
 
Last edited:
Corrective LUTs and look LUTs shouldn't need more than one instance.

However, for the accuracy of color science conversions, it is significant.

Tungsten
tunwb.gif


Daylight
daywb.gif
 
Last edited:
Paul provides a very valuable service, converting a wide variety of cameras to have accurate, neutral color.
Highly recommended
 
You must log in or register to reply here.
Back
Top