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In the form of a Google document, attached here for posterity.

https://docs.google.com/document/d/1MrPrSDpp6PmHPx45LzxTVJt2uCfl0MajA8GVtpWcois/...

(Google's PDF export seems to be broken currently)

Highlights:

- Red, green, blue levels measured using a video capture card, and checked for any odd biases produced by the card and the slightly funny video signals
- Red and green levels are pretty much linear
- On an SMS1, blue isn't, in particular the lowest intensity blue is 22-23% above where it ought to be
- Confirmed with an oscilloscope
- On an SMS2, the blue is more "normal" and the overall intensity is a bit higher (higher range) than SMS1/JSMS
- On a Genesis with PBC the colours are non-linear in a different way

SMS.zip (2.14 MB)

HTML + images

I was wondering if all SMS 1 have the same Sony video encoder chip...

I believe not. I guess it may be VDP related, perhaps unbalanced voltages at the encoder are the root cause. The doc does not list VDP or encoder versions.

so if we have both first revision SMS and second revision SMS using the same video encoder chip we could rule out that...

That's my Google Doc which I do hope to update over time. I didn't even know we were going to find this, so slowly I am getting more details about the captures others submitted. It seems quite clear at this time that this is the VDP, the 315-5124 and not the encoder as it shows in various encoders with that VDP as well as RGB bypasses with that VDP. And it also seems the 315-5246 is always linear.

If you’re going into this rabbit hole, I guess you can scope the voltages from the VDP? How do the RGB out voltages correspond to perceived brightness on a typical TV of the era, compared to a typical PC screen now, especially regarding gamma? Does the progressive scan change that (as the electron beam double-scans the same rows)?

Those are all great ideas. I've written them down for when I magically find time :-) Many thanks.

I did some measurements myself a while back (https://www.smspower.org/forums/15700-SMSVideoOutputLevels), somehow I didn't notice this blue difference you did. This is cool info none the less ~

That is INTERESTING, TimEE, and god knows I am happy to be wrong somehow. I hope more people test and maybe we all learn something. From personal measures and submissions it appears that consoles that have the 315-5124 have this blue push.

It is fascinating to see a more or less linear result with yours.

Always willing to learn more!

Author	Message
Maxim Site Admin Joined: 19 Oct 1999 Posts: 13506 Location: London	Notes & Measures: Nonlinear Blue on Sega Master System 1 & Other Findings by bfbiii Posted: Sat Dec 19, 2020 8:36 pm
	In the form of a Google document, attached here for posterity. https://docs.google.com/document/d/1MrPrSDpp6PmHPx45LzxTVJt2uCfl0MajA8GVtpWcois/... (Google's PDF export seems to be broken currently) Highlights: - Red, green, blue levels measured using a video capture card, and checked for any odd biases produced by the card and the slightly funny video signals - Red and green levels are pretty much linear - On an SMS1, blue isn't, in particular the lowest intensity blue is 22-23% above where it ought to be - Confirmed with an oscilloscope - On an SMS2, the blue is more "normal" and the overall intensity is a bit higher (higher range) than SMS1/JSMS - On a Genesis with PBC the colours are non-linear in a different way SMS.zip (2.14 MB) HTML + images

sverx Joined: 05 Sep 2013 Posts: 2818	Posted: Mon Dec 21, 2020 5:30 pm
sverx Joined: 05 Sep 2013 Posts: 2818	I was wondering if all SMS 1 have the same Sony video encoder chip...

Maxim Site Admin Joined: 19 Oct 1999 Posts: 13506 Location: London	Posted: Tue Dec 22, 2020 12:55 am
	I believe not. I guess it may be VDP related, perhaps unbalanced voltages at the encoder are the root cause. The doc does not list VDP or encoder versions.

sverx Joined: 05 Sep 2013 Posts: 2818	Posted: Tue Dec 22, 2020 11:49 am
sverx Joined: 05 Sep 2013 Posts: 2818	so if we have both first revision SMS and second revision SMS using the same video encoder chip we could rule out that...

bfbiii Joined: 22 Dec 2020 Posts: 3	Hi there Posted: Tue Dec 22, 2020 9:17 pm
bfbiii Joined: 22 Dec 2020 Posts: 3	That's my Google Doc which I do hope to update over time. I didn't even know we were going to find this, so slowly I am getting more details about the captures others submitted. It seems quite clear at this time that this is the VDP, the 315-5124 and not the encoder as it shows in various encoders with that VDP as well as RGB bypasses with that VDP. And it also seems the 315-5246 is always linear.

Maxim Site Admin Joined: 19 Oct 1999 Posts: 13506 Location: London	Posted: Wed Dec 23, 2020 12:04 am
	If you’re going into this rabbit hole, I guess you can scope the voltages from the VDP? How do the RGB out voltages correspond to perceived brightness on a typical TV of the era, compared to a typical PC screen now, especially regarding gamma? Does the progressive scan change that (as the electron beam double-scans the same rows)?

bfbiii Joined: 22 Dec 2020 Posts: 3	Posted: Wed Dec 23, 2020 12:39 pm
bfbiii Joined: 22 Dec 2020 Posts: 3	Those are all great ideas. I've written them down for when I magically find time :-) Many thanks.

TmEE Joined: 31 Oct 2007 Posts: 852 Location: Estonia, Rapla city	Posted: Wed Dec 30, 2020 7:41 am
	I did some measurements myself a while back (https://www.smspower.org/forums/15700-SMSVideoOutputLevels), somehow I didn't notice this blue difference you did. This is cool info none the less ~

bfbiii Joined: 22 Dec 2020 Posts: 3	Posted: Sat Jan 02, 2021 3:16 pm
bfbiii Joined: 22 Dec 2020 Posts: 3	That is INTERESTING, TimEE, and god knows I am happy to be wrong somehow. I hope more people test and maybe we all learn something. From personal measures and submissions it appears that consoles that have the 315-5124 have this blue push. It is fascinating to see a more or less linear result with yours. Always willing to learn more!

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