I think that’s a side effect of the camera’s dynamic range rather than an actual behavior. That is, I believe it’s just bloom/flare-out in the photo.
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Well, maybe the crt brightness is leaking over the mask, if that’s possible.
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You could probably mimic the effect by modifying the mask strength by the inverse of the luminance, but this monkeys with the black level in a way that I don’t love:
OTOH, this also happens with luma-linked beam width, but you and guest have handled that admirably, so maybe this isn’t that big of a deal 
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We need to make sure we’re comparing apples to apples, I think.
For the comparison to be useful, we need a photo of the aperture grille CRT with the individual phosphors in-focus (ie., able to see the RGB strips). Same thing with the shader, it should be a photo of the actual LCD screen (preferably a 4K one), with the emulated phosphors in-focus. Check out the Megatron shader thread for some excellent side-by-side comparisons.
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Crt displays imo had different chromatics/lighting properties. A good example is that you need at least 2x more nits with a flat display combined with a full mask strengts shader to properly ‘emulate’ a 1x nits value crt tv display. The images above might be taken with about the same lighting strength.
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are you saying you need (for example) 200 nits + full mask strength to equal a 100 nit CRT? That sounds right for the 2px masks, which result in a 50% reduction in brightness. For the 3px masks I think you need 3x nits, and for slotmask it’s even worse.
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I started experimenting with -50 mask value with crt-guest-advanced and I am happy with the results. Try and see if this is something that interests you. While using HDR it looks super bright at 200 paper white (800 peak white)
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I wrote/meant you need at least a ‘2x nits’ modern display, but you are quite right about the increasing necessarity for brightness.
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I’m not sure about these nit comparisons as a CRT is a pulse display and a LCD is a sample and hold. Therefore one has a very intense pulse of nits then a steep fall off and the other is constantly spitting out a stream of photons at a relatively steady rate. They’re very different graphs.
Sure you can average out the pulse display but I’m not sure our brains interpret it like that. As in I think that intense pulse is being interpreted as many more nits in total than it actually is spread out over a longer period of time - with the peak lower.
Thats in the temporal dimension alone then take into account the spatial dimension differences.
From my limited testing with a HDR600 monitor it gets reasonably close in brightness to a 2730 PVM. Certainly not quite as bright but I think a modern QD-OLED or LCD will surpass it with 100% mask and a 4px mask. Whether the colorimeters agrees with that over the whole screen is a different matter.
What it won’t do is mimic the pulse though - which is really the next step and is started to being taken with backlight strobing as I’ve said (bored you with 
) elsewhere.
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