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valadaptive / ntsc-rs

Free, open-source analog TV + VHS effect. Standalone application + plugin (After Effects, Premiere, and OpenFX).
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(issue, possibly??) noise is too dark in highlights #97

Open nlolnlolnlolnlo opened 1 month ago

nlolnlolnlolnlo commented 1 month ago

i feel like the way noise is handled in light areas in ntsc-rs could use some work. usually on analog video transfers, the light portions of the image aren't as affected by noise as more median colors. my stupid guess is that the light areas likely don't have the bandwith to get any darker or lighter in the way that neutral tones do. (this is also probably slightly visible in dark areas but it's not as visible.)

could some falloff be added to the way noise is handled or something? this is one of the only things that i think is holding ntsc-rs back from being nearly indistinguishable from real vhs/cvbs at this point.

philipscard_ntsc_ntsc ntsc-rs (noise slightly boosted for visibility) vlcsnap-2024-05-19-18h14m17s235 real vhs

valadaptive commented 1 month ago

At first I wondered if this was some sort of gamma issue, but it seems like YIQ is gamma-corrected in the way I'm currently doing it.

Can you share the test image and preset you're using here?

nlolnlolnlolnlo commented 1 month ago

ntsc-rs_vhs-sp_v8_noiseboosted.json philipscard_ntsc

valadaptive commented 1 month ago

It may just be that the noise is more visible in the highlighted areas for perceptual reasons. I think some of it comes from the "Composite noise" being lower-frequency than the luma noise visible in the VHS tape transfer, and hence more visible.

I've added a "Luma noise" setting in version 0.7.0, and got this result (here's the preset): image

I think it looks similar to the VHS tape transfer, although a bit brighter. Try it out and let me know if it works for you.

nlolnlolnlolnlo commented 1 month ago

the new noise options are very good, but i'm still of the opinion that an option to clip the noise at the bright areas would be a bit more accurate looking.

i've attached some comparisons with large areas of white below: image image

and the clean graphics for both. the comparisons used the preset that you posted above so it's not included. NTSC-720x480-Color-Step-Lin-Gray ntsc_rs_smear_testpattern