FS7: Emulating "EI" mode with custom LUTs (on external devices: Gratical, Odyssey, etc)?

J

jshbckr

Veteran
Emulating "EI" mode with custom LUTs (on external devices: Gratical, Odyssey, etc)?

So I have a Gratical preordered and I am anxiously awaiting custom LUTs on the Odyssey. As it stands, the FS7 will auto-adjust your LUT image based on your EI setting (i.e. they will darken an EI 800 shot that should look overexposed, knowing that you're darkening it in post to clean up noise.) but is there a way for us to emulate this with external devices? And I'm not talking about using the camera's ability to apply a LUT to the SDI outputs.

In my head, I feel like I could bake in a LUT (i.e. LC709typeA) to an EI 800 shot, then shoot the same footage as Slog3, no exposure adjustments. Then apply the same LUT in Resolve to the Slog3 footage, darken it until the exposure matches the baked-in image, then export a 3D LUT from Resolve. So, theoretically, I would end up with a LC709typeA LUT that also compensates for the fact that I'm rating the sensor at 800 instead of 2000.

This way, I could put the LUT onto the Gratical, so I can toggle it on/off instantly with one of the side buttons, retain waveforms, etc.

Think this would work?
 
At the gratical price point you should expect a level of service and support where this happens.

AKA there should be
LC709_800ISO
LC709_1600ISO
or whatever
It should be simple to 'pedal' between them.
At that point there would be no need to fiddle with EI values on the camera unless there was value in changing the camera meta data to accelerate your post workflow.

Same with the O7q

S
 
Hi Josh,

You can modify an existing LC709A LUT in Davinci Resolve for each increase/decrease of stop and thus create new versions if desired for each EI rating.

Is that what you mean and want?
 
morgan_moore said:
At the gratical price point you should expect a level of service and support where this happens.

AKA there should be
LC709_800ISO
LC709_1600ISO
or whatever
It should be simple to 'pedal' between them.
At that point there would be no need to fiddle with EI values on the camera unless there was value in changing the camera meta data to accelerate your post workflow.

Same with the O7q

S
Click to expand...

Great. That's essentially exactly what I want. Not to fiddle with EI settings on the FS7, but rather apply the proper LUTs on my other devices. I just had a shoot where the largest monitor was the 7Q (on the FS700, FS7 shooting internal) so the client always had to look at a flat, slightly over-exposed image because the built-in 7Q LUT (Slog2) doesn't yield the proper image when rating the camera at a lower ISO.


starcentral said:
Hi Josh,

You can modify an existing LC709A LUT in Davinci Resolve for each increase/decrease of stop and thus create new versions if desired for each EI rating.

Is that what you mean and want?
Click to expand...

Yeah, that's exactly what I'd need. I'm used to using Resolve for tweaking color but I've never really dealt with something like this (where I consider it more "scientific"). How would I increase/decrease a LUT exposure by exactly 1 or 2 stops? I'll google around too. Thanks for the help you guys!
 
Really you just need exposure offsets to put before your LC709A. Someone has already created these, I think cameramanben on Sony forums.

If you want to make it yourself, you'd need to load an slog3 based step chart into resolve and then adjust the offset until the value of your middle grey is adjusted similar to the step that was next to it. You can use the show picker RGB value to help with this, then use the scopes to toggle on and off the node to see that your step chart is being properly transformed.

I haven't tried exporting LUTs from Resolve but surely google will tell you how.
 
To some extent, I believe at the price point of the products mentioned one should not have to cook your own. The manufacs should engage and provide.

While cooking ones own 'works' to some extent I would feel that one is 'protecting' yourself by using something more 'official'

S
 
Josh,

If you can't find the slog3 charts then just create a grey image with the RGB value 420 on it. This is "middle grey" for slog3.

Next take this grey image into Davinci Resolve and adjust your OFFSET until it changes to 347 darkening it one stop. You would darken it 1 stop if you overexposed by 1 stop for example.

Here is a list of grey scale values for slog3 incase you want to make more offset LUTs in either direction.

965
886
808
729
651
573
496
420
347
279
219
171
133
114
105

NOTE: these values are specific to slog3 and can not for example be used for slog2, REC709, etc..
 
jshbckr said:
In my head, I feel like I could bake in a LUT (i.e. LC709typeA) to an EI 800 shot, then shoot the same footage as Slog3, no exposure adjustments. Then apply the same LUT in Resolve to the Slog3 footage, darken it until the exposure matches the baked-in image, then export a 3D LUT from Resolve. So, theoretically, I would end up with a LC709typeA LUT that also compensates for the fact that I'm rating the sensor at 800 instead of 2000.

This way, I could put the LUT onto the Gratical, so I can toggle it on/off instantly with one of the side buttons, retain waveforms, etc.

Think this would work?
Click to expand...

This is pretty much what Alister Chapman has done here:
http://www.xdcam-user.com/2015/02/o...alisters-arri-look-exposure-compensated-luts/
 
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