Blackmagic Forum

Hey,

I have a DP who likes looking at the log image (on a monitor calibrated for 709) with just a small contrast tweak which I at the moment just made on the full range image.

Is it possible to map the log image to 709 without effecting the look of the image?

When delivering the rushes I will need to do this in 709 colour space and my best plan for this at the moment is to map the original log image to 709 with a colour space convert effect on a node and then match back up to the image the DP likes to see.

If DP looks at log straight on rec709 monitor, reading it into Resolve rec709 timeline without any input transforms should produce the same image...? But if you do use an input transform, you should invert it in the end and then write it out as if it were still rec709 (although it isn't).

It does indeed produce the same image, although as its raw I think this means it is just the full range showing up on a GUI monitor? My concern is that if I create a LUT from this timeline it would be creating a LUT from the full range video and not mapping the colour space to 709.

It may be as simple as exporting the timeline as Video levels at the final stage? However the look would want to be reproducible down the line by VFX etc so I was thinking a 709 transform at the colour stage was the right way to do it.

This is Redcode shot in RWG/L3G10

Thinking you should be looking into ACES transforms for cross-colorspace uniformity.

jPo, CSI

JPOwens wrote:Thinking you should be looking into ACES transforms for cross-colorspace uniformity.

jPo, CSI

I am picking up this job on the block break, and unfortunately have no time for switching to ACES.

Dylan Evans wrote:It does indeed produce the same image, although as its raw I think this means it is just the full range showing up on a GUI monitor? My concern is that if I create a LUT from this timeline it would be creating a LUT from the full range video and not mapping the colour space to 709.

It may be as simple as exporting the timeline as Video levels at the final stage? However the look would want to be reproducible down the line by VFX etc so I was thinking a 709 transform at the colour stage was the right way to do it.

This is Redcode shot in RWG/L3G10

If it is log, it isn't raw anymore and vice versa. What DP is looking at is log misinterpreted as rec709. If I understand correctly, you want to reproduce this while still keeping track of what the data actually represents (for vfx it is important)? VFX will be able to reproduce the look by doing proper log>linear transform to get data to working space and for viewing, do lin>log to get data to starting point and then either add reverse transform to compensate for viewer lut or turn off viewer lut completely. How to handle levels in Resolve is something I can't explain good enough, someone can hopefully describe what to do.

You already are viewing the image in Rec 709 space, that's why it's log. Rec 709 can only display 10 linear stops, so the image is log encoded to fit all the DR in a 10 stop environment. HDR is about to change this but it's still a ways off. Do what was suggested earlier and export the footage without a colorspace transform and you're good.

Hendrik Proosa wrote:If it is log, it isn't raw anymore and vice versa. What DP is looking at is log misinterpreted as rec709. If I understand correctly, you want to reproduce this while still keeping track of what the data actually represents (for vfx it is important)? VFX will be able to reproduce the look by doing proper log>linear transform to get data to working space and for viewing, do lin>log to get data to starting point and then either add reverse transform to compensate for viewer lut or turn off viewer lut completely. How to handle levels in Resolve is something I can't explain good enough, someone can hopefully describe what to do.

Sorry yea, what I wrote there wasn't clear - I just meant it was showing according to the metadata contained in the raw file - in this case RWG/L3G10.

You already are viewing the image in Rec 709 space, that's why it's log. Rec 709 can only display 10 linear stops, so the image is log encoded to fit all the DR in a 10 stop environment. HDR is about to change this but it's still a ways off. Do what was suggested earlier and export the footage without a colorspace transform and you're good.

This doesn't make complete sense to me - RWG/L3G10 can be transformed into a 2020 or 709 colour space - if there is no other transform happening in camera then surely it is a oversized colour space (RWG) being displayed on a monitor that displays less than this (709)...

To be clear - are you saying that the following workflow:

Import footage>do basic cdl adjustments in color page>export to DNX36 (do I need to select 'video' instead of 'auto' levels?)

Will produce files that are in the correct (709) colour space?

I understand your dop, if shoot also seeing log. I usually prefer to see log with difficult or underexposed shooting to understand where i can work and where i have only rubbish.
I setup project color management with
Managed davinci yrgb
Input log camera
Timeline log camera
Output rec 709
That mean i have the ability to see original log, then i can put down shadow, up light, push a saturation.
Different camera give you different management, different quality allow you different workflow. If i have a good quantity of data (10 bit enough) you can work like this, if you have a Sony log 8bit 4:2:0 ultraflat you cannot do miracle
But sometimes see direcly log allow you to understand if you must spent time on some shadow or not, on some highlights or not

Inviato dal mio E6653 utilizzando Tapatalk

Thanks Carlo,

Our DP wants to maintain this look throughout the post production line. For now at least I have just created a 709 LUT which matches the look of a Log image with a bit of contrast.

I originally did this with a colour space transform, but this does not get saved into an exported cube so I ended up taking a 709 LUT and modifying it to match his loggy look.