Sony Megatron Colour Video Monitor

RetroArch Additions Shaders
#1238

Hi @MajorPainTheCactus

Thanks for posting these pictures, let me first just say they look astonishing! I wouldn’t be able to tell the shader ones from real CRT if they would’ve been posted on their own.

The interesting and great part of course now is that you have the CRT for close inspection and comparison. As you mentioned the gamma part is the more obvious difference when comparing them side by side.

Do you have the ability to run the 240p test on your CRT and actually have the CRT placed side-by-side with the LED? I know you’ll have your own methods, but if I were doing the calibration I would do two things:

  • Run 240p test suite on both, go to the white screen, and make sure the luminance of the white screen on the CRT matches that of your shader output on LED. Note that is very valid to use the “Contrast” on the CRT to bring it in line with your shader output luminance on the white screen! You don’t have to do everything on the shader/LED side!
  • Run 240p test suite Gray Ramp test on both and make sure the darkest value bar (the “8,8,8” bar) is just visible when looked at in a dim room, while covering the bright bars with your hand or a magazine. Note again adjusting the “Brightness” on the CRT is equally valid. The goal is to have them both matched, so adjusting on both is a valid strategy.
  • Reiterate the previous two steps until both the white screen and the gray ramp look exactly the same on both the CRT and the LED with shader output. Of course this is only possible if you’re able to run the CRT and the LED/shader in a physical side-by-side comparison, so hopefully that’s something you’re able to do.

If after this process there’s still a difference then it could be an option to add the various Gamma Type functions on gamma_in and _out as parameters, as we talked about previously, to see if for example a change to power law from 709 or other combination of gamma function/type on gamma_in versus the gamma_out type function could “dot the i” :slight_smile:

It would be super interesting to see your three phothograps again after the CRT and shader have been matched on gamma! In any case great stuff already, thanks for posting the comparison!

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#1239

Thanks for the calibration tips! So sadly I haven’t got them side by side as I haven’t been bothered to move my PC and monitor into the living room and I’m certainly not going to try lumping the 50KG PVMs into my office. :rofl: BUT I can see the two screens at the same time - just from a bit of a distance. I do have 240p t at suite on both and have done calibration comparisons in the past but I should do this again as it’s a long (development) time since I did it last and the gamma has all changed since fixing the precision bug and other things.

The main issue with luminance is that my 600-700 nit LCD monitor can’t reach the brightness of the CRT when the shader is on.

That’s actually a lot of the difference you see in the above pictures TBH as my camera doesn’t have low enough ISO to stop the CRT blooming and clipping the images and giving slightly false results. But then again phone cameras aren’t perfect anyway.

I’ll definitely calibrate the gamma again and post the pictures up.

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#1240

I’m certainly not an expert on the subject but maybe you can temporarily lower the brightness of the CRT to match the LCD at least initially and do your calibration of your colours, gamma and contrast at that level, so you get the best case for the LCD, in terms of matching the CRT, then you can revert the CRT to the best case for that.

Normalizing the brightness of both displays to the lowest common denominator should also assist with your camera issues.

Again, I’m no expert, just a thought.

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#1241

Yes good idea, I have a feeling my PVM doesn’t have a brightness control when taking scart though.

1 Like
#1242

It would be very unusual for a studio monitor not be able to control brightness. Being connected via scart should have nothing to do with it?

According to the manual of your Sony PVM 2730QM on page 5 and on page 3, you can control Brightness (black level I think) with button “4” and “Picture” level (meaning old fashioned “Contrast” I think) with button 14.

See page 3 here: https://archive.org/details/sony_PVM-2730QM_Service_Manual/page/n1/mode/2up

And page 5 here: https://archive.org/details/sony_PVM-2730QM_Service_Manual/page/n3/mode/2up

It does say that some controls only work when “Set the MANUAL CONTROL switch on the rear panel to ON” (see page 4 and 2 at the bottom).

EDIT: and on page 2 there’s additionally under “Troubleshooting”:

Symptoms: No controllable keys although the POWER switch is turned. Corrections: Press the CONTROL key.

Page 4 note: Press CONTROL key after power is turned on to illuminate the control keys or indicators

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#1243

Yes as I say it was a feeling, you could well be right but I do know for certain some controls dont do anything and I have two of them that work that way. Having said that maybe it’s the ‘hue’ controls. I’ll have a play around.

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#1244

So just just played around with brightness and whilst I was wrong in that its disabled, I was right one way, in that lowering it doesn’t do anything (not that I could perceive in a lit room at any rate) i.e it’s at its darkest but who knows in combination with contrast and a dark room maybe I can get some leverage our of it.

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#1245

Just curious, did you try both Brightness (button 4 in manual) and Picture (button 14 in manual)? Especially the Picture button should work on Luminance, did you try this button on the right side of your screen?

To make it clear what we call “Brightness” these days with LED monitor, it is the equivalent of “Contrast” or “Picture” control from the CRT days. So if you want to lower the max luminance/brightness on a CRT you actually need to lower “Picture” or “Contrast” and not “Brightness” (which on a CRT controls the black level and does little to max luminance).

I can only say that if you can’t turn the screen close to entirely black, something is definitely wrong with your PVM.

Edit: so yeah you need to lower “Picture” on your PVM (button 14 on the right) to lower the brightness. That should do the trick.

If you want to read up on the (confusing) terminology used in the CRT era, read this from Charles Pontyon, the CRT expert, here CRT “Brightness” and “Contrast” (Picture) controls

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#1246

Yes I was just saying brightness doesn’t go lower. I don’t tend to do any calibration stuff during the day and so that’s why I havent taken further steps - the problem is at night is the only time I get to work on other projects and so finding time is difficult.

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#1247

Hi @MajorPainTheCactus !

I’ve been doing some extended testing and have some good news! I’ve now been able to also get a balanced Gray Ramp in HDR mode!

Just for the sake of completeness I’ve tested all three SDR modes (709, sRGB, DCIP3) since they each use a different gamma curve and tested HDR mode. I’ve used the 2730-sdr preset for SDR and the 2730-hdr preset for HDR. So four tests in total.

After loading the preset I changed the “Brightness” +0.15 to “0.00” and TVL to 1000 in all four test, additionally I tweaked CRT gamma in the three SDR tests and for the HDR test tweaked Max Nits, Paper White Nits and CRT Gamma.

To get right to the issue, to get a balanced Gray Ramp in HDR mode I needed to lower CRT gamma from its default 2.4 to 1.9 and then lower max and paper white nits to around 300 each (even though my monitor is HDR 400) and then I get a balanced Gray ramp, while remaining a bright enough screen as well!

So what I’ve noticed is that your 2730-SDR and 2730-HDR preset differ in their preset CRT gamma, the 2730-sdr version sets a preset value of CRT gamma 2.00 but the 2730-HDR preset doesn’t set a preset CRT gamma, so it defaults to the parameter.h default of 2.40!:

2730-sdr preset

loads "#reference “shaders/crt-sony-megatron-sdr.slangp” which has a gamma_in preset value:

#reference "crt-sony-megatron.slangp"
hcrt_hdr = "0.000000"
hcrt_gamma_in = "2.000000"

2730-hdr preset

loads "#reference “shaders/crt-sony-megatron-hdr.slangp” which does not have a gamma_in preset value:

#reference "crt-sony-megatron.slangp"
hcrt_hdr = "1.000000"

I think if you add the " hcrt_gamma_in = “2.000000"” also to your 2730 HDR preset, it may save a lot of headaches for people.

Because, if I change CRT gamma to anything above 2.1/2.2 let alone its default 2.4 there’s just no way I can get the gray ramp balanced, the whites will always be blown out or the whites will be good when lowering paper white to something about 170, but then the darks and the whole screen will be way to dark.

Now onto SDR mode…

Previously I already mentioned that SDR mode was fine for me using the DCIP3 colour space with its power gamma, and now I’ve matched up the SRGB and 709 almost through changing the CRT Gamma as follows:

SDR mode:

SDR colour space: DCI-P3, Display Gamma: 2.40, CRT Gamma: 2.30 == perfect gray ramp
SDR colour space: sRGB,   Display Gamma: 2.40, CRT Gamma: 1.90 == close to perfect gray ramp (dark values fall off slightly to steeply)
SDR colour space: r709,   Display Gamma: 2.40, CRT Gamma: 1.70 == close to perfect gray ramp (dark values fall off slightly to steeply, and even a bit more than sRGB above)

Note how for sRGB and r709 I increasingly need to lower the CRT gamma.

Maybe I’m premature in my conclusion, but it seems, at least for my setup, that with the power law gamma function (which the sdr dci-p3 setting is using as gamma function) allows me to create the most balanced gray ramp in that the darks don’t fall off too steeply, but overal a really great even spacing between the bars from dark to bright. Maybe it would be the same for other users? In that case possibly it could be considered to add an option for the 709 and sRGB colour space, to be able to switch between their spec gamma curves and power law gamma curve.

Anyway thanks again for the shader and putting in all the effort, much appreciated!! :+1: :ok_hand:

3 Likes
#1248

As a quick response to the HDR section: so what you have hit upon is the reason why all HDR applications really need a calibration process. Basically because no display can currently display the full rec.2020 spec i.e 10,000 nits and the wide colour gamut (as we’ve discussed before) then what looks good on your monitor may not look good on mine and vice versa.

So as you’ve correctly identified these calibration screens behind the scenes tweak the max nits, paper nits and gamma values of said applications and that is basically what we really need in RetroArch but I didn’t have the time or resources to create those screens when I added HDR support to it.

Basically you need to tweak these values for your screen as these values are for my screen i.e 700 max nits, paper nits and 2.4 gamma (in). These values do give a correct grey ramp on mine so that’s what I’ll keep.

Maybe I need to give these instructions on the shader params screen though.

4 Likes
#1249

This is great work @rafan! What display do you use?

Will you consider packaging a preset pack or at least posting all of your modified preset code as you go along or when you go through all the Sony Megatron Color Video Monitor presets that you use. This would be a great help to users like myself who don’t have as much knowledge and understanding of how colour systems and calibration work!

Brilliant work in improving this awesome shader!

#1250

Hi @cyber - that’s my point you can’t make a preset for this with HDR. It’s different for everybody’s display (assuming they have different displays of course).

SDR is different in that a lot of people’s displays are capable of the full rec.709 standard.

1 Like
#1251

That’s why I asked @rafan what display he uses. His settings won’t work for everyone but they just might happen to work for some with the same or similar displays. They might even work better than the defaults on different displays for some users.

Maybe in time others might share their calibrated presets as well and eventually what started off as a couple presets might someday grow into a large database.

When more and more users start diving in and figuring stuff out about the shader and how to improve the experience on their own then share their presets and findings that’s what will create and generate more buzz and excitement around the shader as the community of users start to grow.

1 Like
#1252

I don’t know, I think a calibration wizard is the way to go for this. A thousand and one presets would surely just confuse users. At least this is how games deal with this problem.

2 Likes
#1253

Hey @Cyber

It’s a Samsung Odyssey G7. It’s a very nice 1440p monitor. I think somewhere down the road I would want to “upgrade” it to a bright 4K monitor though, as it would be very neat to comfortably use slotmask and lower TVL settings in the shader for an even more close CRT experience. With my current monitor only TVL1000 setting is up there for enough brightness.

In that regard I’m also curious about OLED, since you own one, does it bring a more CRT-like smooth(er) motion with fast scrolling stuff in your opinion? How would it compare to a good LED motion wise?

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#1254

Hmmm…my OLED is “only” a 60Hz one. I’ve recently switched between a 4K LED and my OLED and I couldn’t wait to get back to my OLED mainly for the contrast, the better black levels and lack of blooming.

I don’t have any issues with motion clarity on either. I don’t always try to nitpick when I’m immersed in a game though. I have noticed that I couldn’t see the mask pattern clearly in the backgrounds during fast moving or scrolling sections of games. On objects like the main characters (when stationary) or status bars or even static backgrounds in a boss arena or title screen for example it’s not an issue. In general it isn’t an issue at all at least for me as it’s only something I notice if I’m looking for it. Same goes for judder.

I would assume that something that can do BFI properly and still have enough brightness left over so you can see everything properly might be a sight to behold but for me who only has distant memories of CRTs to compare its more than good enough even without.

On my OLED TV, I notice trails from fast moving bright objects on a dark background quite frequently even without tricks like afterglow in my presets.

When I switched back my biggest disappointment was realizing that most of the mask patterns that I used that worked quite well on my LED TV looked really off, incorrect and downright horrible on my OLED TV.

That motivated me to investigate this further and further because others had written off OLED TVs and good colour mask emulation which I wasn’t satisfied with at all and I eventually stumbled upon specific mask patterns that actually worked much better (at least well enough) with OLED TVs.

So no matter which display technology you choose, there’s always going to be some sort of tradeoff.

I think a good 4K miniLED TV might be a good compromise between the two competing technologies.

Specifically one of the new TCLs which has a relatively conservative dimming algorithm which handles difficult for miniLED scenes like starfields very well.

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#1255

The photo was to demonstrate the improvement to the mask on my OLED, but the overall image still had clipping/crush issues in the highlights and on similar colours unless using the JVC presets as described here:

However, using the new colour-accurate parameter, all these issues are gone unless pushing the paper-white too high. Everything looks correct with paper-white at around 550 (nits at 720). Thanks for the amazing update!

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#1256

Fantastic great to hear! What model OLED are you using again?

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#1257

It’s LGs latest 42 inch ( OLED42C2)

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