HDR scopes - why a dotted line at 200 nits?

Not sure when this started, maybe when I updated from Resolve 17 to 18 but it's there regardless of scope setting "Show Reference Levels" being on or not. It's also there regardless of using automatic or custom color management.

Why is it there? To what aim?

I guess it is related to 203 Nit Support for SDR to HDR. See Page 219 of the most recent manual for an explanation.

Thanks for the reply, however "203 Nit Support for SDR to HDR" is for when mixing both SDR and HDR in the same project. Since I'm not using any SDR media in any of my HDR projects I dont need it, don't turn it on, so maybe the dotted line is there for some other reason.

Thanks for the reply, however "203 Nit Support for SDR to HDR" is for when mixing both SDR and HDR in the same project. Since I'm not using any SDR media in any of my HDR projects I dont need it, don't turn it on, so maybe the dotted line is there for some other reason.

203 nits is also the (highly) recommended level for all white titles and text.

203 nits is also the (highly) recommended level for all white titles and text

Thanks for the suggestion. I zoomed the scope waveform and sure enough the dotted line is actually a smidgin higher than 200, (fully expand the screenshot to see)

203 nits is also the (highly) recommended level for all white titles and text

Thanks for the suggestion. I zoomed the scope waveform and sure enough the dotted line is actually a smidgin higher than 200, (fully expand the screenshot to see)

FYI - 203 nits is recommended but not set in stone. There are factors that will change it including background color and intensity. It is also recommended when grading for 1000 nits. For something brighter or dimmer, you will need to adjust.