FAQ So here come LUTs again...

moldcad

moldcad

Veteran
I have the Gratical Eye and use it sometimes with my FS7, but most of the time on my GH5 or A7Rii rigs (it takes SDI signal from my Shogun Inferno). As I'm a believer in proper 709 MLUT monitoring when recording Log, I tried the A7 S-Log2 preset on the Gratical but it's no good (too dark, even with 2 full stops over-exposing). So I downloaded a LUT pack from Alister Chapman website, and - after having converted the three most useful (Normal, 1-OVER and 2-OVER) 3D LUT files to CUBE 1D format (Gratical only supports 1D), I was a happy camper for the first couple of minutes as the picture in my EVF became very much representative of waht I was seeing with my own eyes. However, I then noticed that all overexposed areas - however small - are displayed with very weid colors; difficult to explain but a white piece of paper on my desk was rendered completely black!

Now - please tell me that this is the 1D LUT format which is at fault here, and not my Gratical OLED marvel :) Of course, I believe Alister would have noticed if his original 3D LUTs produced similar artifacts, so it's either the conversion process with Briz LUT Converter, or the very nature of 1D LUTs which is behaving on me... Pity, as otherwise those LUTs are spot on for the A7 S-Log2 picture... Please tell me what can be done about it? Before you send me over to LUTCalc and similar tools, I admit I've no experience in creating my own LUT files - so perhaps someone could help me get properly working 1D LUTs from sources like these:

http://www.xdcam-user.com/wp-content/uploads/2016/05/Alisters-LUT-Kit.zip

TIA; Piotr
 
I can’t speak directly to your gratical issue, but I have had something odd happen recently as well. I was using Alister’s 709 800 (-1 exposure) LUT on my smallhd 501. Exposure and colors seemed fine for the most part, but I noticed things like a blue shirt would go crazy with rainbow colors dancing across it. Thankfully this did not transfer to the final footage, and was only happening when using the 501 and lut.
 
In my case, I am also wondering if the problem is that Allister 's are for the A7Sii not R. The native ISO for the former is 3200 - what is it for the A7RII, 800?

Anyway I'd appreciate it very much if some good soul helped me devise PROPER 709 MLUTS for my camera, and in 1D format, too...

Piotr
 
Among the LutCalc presets, there is no A7Rii so I don't even know which ISO to adopt as "native"; is it 800 (the minimum value selectable when in S-Log2/S-Gamut?

Piotr
 
In LUTCalc, just pick the generic camera preset. ISOs aren't important here. Set it to 1D. Then you can apply a stop correction if you want to lighten or darken the image you see. I don't know what input range and output range your Gratical needs. Probably they should both be set to the same thing, either 100% or 109%. 1024 points is more than enough. Rec gamma is the input: S-Log2 or 3. Out gamma is the output: pick linear / Rec.709, or any of the other display modes like a HyperGamma or LC709.

Edit: Since you are using the loop output of the Shogun Inferno, I would apply the LUT there instead of in the Gratical. The Shogun can use 3D LUTs, which will give you proper colors when you are shooting in a gamut other than BT.709. Set the Shogun to Custom Look mode to load LUTs, and turn on Output Look so it's applied to the SDI output. It takes 3D Cube LUTs from LUTCalc. For the Shogun, in LUTCalc the input and output ranges should be set to 109%.
 
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I did generate a LLUT file with LutCALC - testing later today. As to the Shogun output idea, I'm not sure if I can run AtomHDR and output different (custom) look at the same time...

Piotr
 
OK, guys - I spent a couple of hours creating & testing various LUTs for my Gratical (BTW, after you select MLUT as opposed to grading LUT, the Gratical appears in the Type of LUT drop-down list - so no place for error here). Unfortunately, I do not like any of a dozen LUTs I created :( Either they are too dark, or when brighter they do not handle highlights nicely. By far the best MLUT I ever used my Gratical with has been the FS7's MLUT (709 (800) is it?).... I did try 709(800) on LUTTCalc output, but still no joy.

Is there a way to get hold of the very MLUT file off the FS7? I could convert it to 1D and be good to go...

Piotr
 
Success! I checked the Knee option, and the highlights now roll-off nicely in my Gratical EVF (LUT based on 709(800%). :)

Piotr
 
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