Adding IDTs to Resolve

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(Attila Bakos) #21

I have built an IDT for Fujifilm’s F-Log. But I’m not sure if I should treat the footage as full range, or video range when it comes to linearization. See the specs here: F-Log Datasheet
The document says full range, but it maps 10bit code value 95 to IRE 3.5, which is a clear sign of video range.

(Nick Shaw) #22

It is a question of terminology. Unfortunately the terms “full range”, “video range” etc. are used by different people to mean different things; often the opposite of what others mean. The fact that they say that “it is Full Range to make effective use of the bit wide of the video signal” and their equating code value 95 with IRE 3.5 is consistent with an encoding which should have Data Range set to Full in the Clip Attributes in Resolve, for example, and which would produce IRE 3.5 if interpreted as Video.

But really the only way to be sure is to shoot with the lens cap on, and examine the recording.

(Attila Bakos) #23

When the lens cap is on, blacks are around 9 IRE according to Resolve’s waveform when data range is set to full. This is the default since the Fuji files have a full range flag and Resolve interprets these files as full range. When I switch data range to video blacks are at 3.5 IRE.

(Nick Shaw) #24

So Resolve’s default interpretation is correct. 95/1023 = 0.092864, which is the value of the constant f in the white paper. Therefore a DCTL using the formula in the paper will correctly linearise that to zero.

So the 3.5 IRE mentioned in the paper refers solely to the level you would see on a waveform connected to the camera, which was interpreting the data ‘on the wire’ as ‘video’.

(Attila Bakos) #25

Yes, that’s what I’m seeing too, thanks for your help! Does this also mean that I will have to ask the users who record externally to switch their footage to full range in Resolve? Prores is interpreted as video range by default. So when you import the externally recorded files, you see that blacks are at 3.5 IRE and highlights go up to 109 IRE.

(Nick Shaw) #26

Correct. Same as you have to for externally recorded ProRes S-Log(1, 2 or 3) from Sony cameras.

EDIT: Do verify that, though. Some external recorders have range scaling options for HDMI inputs, and those settings can mess up assumptions you may make!