Guest does not work with HDR but traditional methods are used to simulate the same look.
The Megatron was designed to use the brightness of the display to mitigate the traditional methods.
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Thank you for the clarification.
I had a run with Megatron using one of the PVM settings.
I must confess that I didn’t notice the text within the shader that explained that max lum and paper white settings from the shader would override RA before asking my initial question.
Anyway keeping max lum and paper at 700 plus inverted RGB gave the best result.
I had to restart RA for the effect to apply.
I noticed that whites were a bit overblown in Capcom games so i changed the gamma value to 2.4 as input and that helped.
I own several BVMs (20E and F series) I will compare the output of my OLED to one of them to get an idea how close / far I may be from such monitors (of course this is not apple to apple comparison)
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Hi Miaou! Sorry for the delayed response, I’m a bit busy at the moment but aren’t we all! 
So in answer to your question the Sony Megatron is a true HDR shader (in that it uses HDR buffers and swapchain) and as such will override the settings in RA.
You need to definitely enable HDR in Windows that’s a must. As for why it looks washed out - that is almost certainly because HDR is not on somewhere - check the shader settings and make sure it’s set to HDR and then work back up the chain from there - RA next, Windows after that, your gfx card, then your cable and then your display. Phew!
This shader should look alright on an OLED, it’s not perfect because of the extra white sub pixel but that only gets turned in very bright areas. Its mostly alright though - much more important is that you don’t have any kind of sharpening on.
Anyway let me know how you get on.
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Yes you’re right you won’t get a perfect image but I think it’s wrong to say that guest’s shader or any other for that matter will resolve that issue - we can’t remove those extra sub pixels as you know.
What guests is better at doing is supporting low brightness screens (at the expense of CRT accuracy) - you might put OLEDs in that low brightness bracket but I’ve seen reasonable results.
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Hopefully we can get to the bottom of your washed out colours - it’s definitely a HDR setting not quite set correctly. HDR is currently a bit of a pain not being the default and having to be switched on in a whole slew of places.
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Yes to all you said but just to add that although it’s not a native HDR shader Guest does work with the RA built in HDR shaders I made i.e just turning on HDR in RA.
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Your problem will be brightness when trying to match those PVMs/BVMs - the later models are incredibly bright allowing them to have much narrower scanlines which helps with motion blur.
Are you still getting your discoloration?
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Hello MajorPainTheCactus 
Apologies for the late answer, I was also busy here…
So turning on HDR in windows appears to mess things up and I am not sure why.
As reported in an ealier post what appears to work for me is to leave HDR off in windows but activated in RA.
I noticed that when HDR was on in windows and RA launched it would deactivate HDR in windows but keep some kind of HDR applied (if i tried to summarize it would be that the picture I get is SDR within an HDR container) I am not sure if this is a bug in windows or some other conflict.
So if I leave HDR off in Windows when I launch RA the HDR icon will pop up on my screen indicating that I switched from SDR.
When i enter a game the colors are good now (i use aperture and 1000 tv lines as i love the very sharp look of BVM screens) the only small adjustment that needs to be performed then is on the gamma side.
I set input level to 2.30 as I feel the overall contrast of the picture is better on my screen.
I am plugging my neo geo (RGB bypassed) into one of my BVM as we speak as I was using games like Pulstar, Real Bout or Metal Slug to compare, I may also try Mister or Retroarch through CRT Switchres to run Capcom games.
I know it will not be an exact comparison due to the different nature of the screens but i just want to get an idea.
Quickly editing upon results:
So no results are not good, for some reason whites are burned when using HDR.
One example is the beach arena is Real Bout Special the fine details in the bright area of the beach are lost when running RA in HDR while they are properly nuanced on the BVM either running the original hardware, mister or RA using CRTswitchres.
Switching to a SDR shader fixes this this as well.
I have to go for today but i will test again
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So if you don’t switch on HDR in Windows you aren’t using HDR. You must switch over to HDR in the Windows itself and then switch on HDR in RA and then use a HDR preset for the Megatron.
First ignore the Megatron and just get HDR working in both Windows and RA. The colours should not be washed out and you should see the white text in the menu ‘glow’ and the colours should be ‘vivid’ in game. Play around with the HDR settings in RA at this point to get things looking right for your display.
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When using vulkan in RA I don’t need to enable hdr in windows, but if using dx I must enable hdr first. This is on win10
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I confirm what Wilch stated,
Once RA opens the HDR logo pops up evidencing the fact that the display switched from SDR.
Triggering HDR from the windows settings does not solve the loss of details in the bright parts of the screen.
I tried to reduce Paper White as I thought it was linked to this but the result is that the screen looses brightness but does not restore the overly bright parts of the screen.
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I just found out about this shader/thread, and love it.
After returning to RetroArch recently, and finding out that it supported HDR now - the very first thing I did was set up my own Royale presets that didn’t clip whites and used HDR to make up for the loss of brightness - so I’m on board with the concept.
However, I’m running into an issue using these shaders - either in Vulkan or d3d11 mode. I’m getting very strong color casts while RetroArch is in focus.
The Viewsonic A90f shader adds a very strong green tint, for example.
If I bring another window on top, like the Windows Magnifier, colors look as I would expect (and the output remains HDR).
It seems like this may be related to “HDR shaders” that override RetroArch’s config, as I don’t see this when using Royale with my custom settings.
I’ve tested this in both the Steam version and the latest download from the site (with updated shaders).
EDIT: I should also mention this is at 4K.
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Ok so Id first of all get it working on Windows with D3D11 or D3D12 as they are the most robust versions of HDR (I developed all versions for RA). Then move onto Vulkan once any other problems have been ironed out.
Yes ok as I said to @Wilch try using D3D11 or D3D12 first and see if the problems stay or are resolved. Do let me know!
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Right ok this is very interesting! So if I’ve got this right when you’re using the Sony Megatron shader in HDR you do get this problem and when you use your Royale preset with HDR you don’t?
Could you post a very close up photo so I can see what’s happening at the phosphor/pixel level?
Is there anything odd about your window setup ie do you have RA in Windowed mode, do you have multiple monitors with differing resolutions or some other out of the ordinary thing?
What’s your gfx card, what’s your display and what’s your driver version?
HDR is working fine for me using all drivers. I’m using vulkan so I don’t have to turn hdr on before loading retroarch 
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Sorry @Wilch I appear to have got mixed up with comments with yours and @faxesystem 
faxesystem did you get your washed out issues ironed out? See last few comments of mine replying to Wilch.
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Seeing that everything is working fine for you, can you post a couple close-up photos of some gameplay off your screen using 300TVL Mask with Reversed Layout please?
Thanks a lot @Wilch. That doesn’t seem to look right to me. I’m talking about the overall colours not the subpixel layout here.
Does it look normal in person?
I’m assuming the top image is RGB, while the bottom is BGR layout?
Both seem to be somewhat misaligned though. I’m seeing an either extra column of red in the top picture, or a 1 column gap between red and green. In the second picture I’m seeing some overlap between the second column of green and the first column of red.
@GPDP1 said that that’s supposed to be RRGGBBX. I wanted to compare it to CRT-Guest-Advanced’s RRGGBBX which seems okay at least on my 2016 OLED TV when the layout is flipped.
CRT-Guest-Advanced actually displays RRBBGGX when flipped however, so I don’t know if that could be the reason why it works correctly.
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