NTSC-M vs NTSC-J

[radorn]

I'm from PAL land and all consoles I have are PAL except for an American N64.

I have Bt878 based PCI capture card which I use with DScaler. I've extensively tweaked the low level settings in DScaler and also adjusted the output scale of the Overlay video surface in my GPU driver options.
It's been a while that I don't do any of that stuff so I'd have to check all again for details. The resumed version is that I get the most accurate picture possible.

I have noticed that my NTSC captures looked wrong compared to PAL. The main problem was it was all too dark.
I considered many possible causes:
1: The known differences between PAL and NTSC Nintendo AV cables would make using PAL cables on NTSC result in a picture that's too dark. But I was using an S-Video cable bought on the interntet and most of these are NTSC-Style. In fact, on my CRT TV I have to add a 75ohm when using the same cable with my PAL N64 to avoid the washed out look.
Interstingly, the capture card seems detect and compensate for this excess in signal levels, as it gives me a correct looking picture for PAL without the resistor too.
2: I thought that, maybe the card, having been bought from a British eBayer, was not really NTSC friendly. Even the TUNER is adjusted for British PAL broadcast norm and wouldn't play well with Spanish reception (back when my cable company still converted some channels to analog), the audio frequency being different.

But that wasn't really the case at all. I stumbled on the solution by luck, while fooling arround.
Turns out that my American N64 seems to output NTSC-J instead of NTSC-M. According to the oracles of the internet, there are some minor differences between M and J, one of them being the black level. https://en.wikipedia.org/wiki/NTSC-J#Technical_definition
When I selected NTSC-J in DScaler, immediately everything looked the right brightness.

Now, often times, when you see videogame captures on the internet, they look washed-out. Black is sort of gray and everything looks white-ish. I'm postulating that this would be the expected result if the source was NTSC-J decoded as if it was NTSC-M, and then, manually or automatically, a filter was applied to raise the brightness level to improve visibility, messing with the black level.
I have seen this not only on NTSC N64 captures, but also in at least GC and PS2 captures too.
Could it be that all this time Japanese made consoles have been putting out NTSC-J instead of M and nobody(?) has bothered with it?
Could it be that good quality CRTs can detect this and deal with it properly? but most (all?) capture hardware can't?

I only have my American N64 and this observation to go by. Is this more or less known among the experts here? I've tried to look this up in many ways and I've been unable to find anything.

[radorn]

I've dug up some old captures that I did when I noticed this.


rom_USA - hw_NUS-001(USA) - output_SVIDEO - input_SVIDEO - decoded_NTSC-M


rom_USA - hw_NUS-001(USA) - output_SVIDEO - input_SVIDEO - decoded_NTSC-J


rom_USA - hw_NUS-001(EUR) - output_SVIDEO - input_SVIDEO - decoded_PAL60

All are taken with an S-Video cable I got from the internet. I once had another svideo cable which provided a really poor quality image. This one is better but there's still this dot-crawl like patterning all over the picture (not just on vertical edges). I assume this is caused by presence of chroma in the luma pin, but what's the reason for that? wire crosstalk? chroma leaking onto luma at the source (the N64)? more details here: http://nfggames.com/forum2/index.php?topic=6316.0