Dialing in CRT colors for 7800

[oakcitycomics]

I recently picked up an old wood grain 1991 RCA CRT to use with my RF systems. It was still in the box from a nice old couple who had it since their local Roses closed down around that time. Who remembers them haha

 

Anyways I'm trying to dial in the color as close as possible for the 7800.  My only other CRT's I have are two PVM that only work with RGB/Composite and a 2008 Toshiba that displays the 7800 colors complete wrong with out question. 

 

How accurate are the colors on the stock photos here on Atari Age. I'm aware they are emulator screen shots form the looks of them. Using this screen shot from Atari Age of Commando as its easy to replicate. 

 

[+x=usr(1536)]

Don't assume that screenshots of emulated games are 100% accurate.  They're probably fine, and generally OK for reference, but taking them as empirical evidence of how a game should look in terms of colour can be misleading.  Different versions of even the same emulator can have huge differences in video output.  And how a screenshot appears on one computer's display will be different to some extent compared to another display; your CRT may not even be able to match those colour ranges.

 

What I'm saying is that if things look acceptable to you, then great, go with it.  But because this can easily become a case of better being the enemy of good enough, don't knock yourself out trying to get a perfect match for a screenshot.

 

With that out of the way: is there a particular issue you're trying to solve?  I'm running my 7800 on the same CRT all of my RF-based systems attach to, and I've made zero changes to the picture settings.  They're probably not optimal, but everything looks fine by me.

[oakcitycomics]

8 hours ago, x=usr(1536) said:

Don't assume that screenshots of emulated games are 100% accurate.  They're probably fine, and generally OK for reference, but taking them as empirical evidence of how a game should look in terms of colour can be misleading.  Different versions of even the same emulator can have huge differences in video output.  And how a screenshot appears on one computer's display will be different to some extent compared to another display; your CRT may not even be able to match those colour ranges.

 

What I'm saying is that if things look acceptable to you, then great, go with it.  But because this can easily become a case of better being the enemy of good enough, don't knock yourself out trying to get a perfect match for a screenshot.

 

With that out of the way: is there a particular issue you're trying to solve?  I'm running my 7800 on the same CRT all of my RF-based systems attach to, and I've made zero changes to the picture settings.  They're probably not optimal, but everything looks fine by me.

My main objective is color accuracy not so much as the tone of the color. For example the 7800 on the newer Toshiba CRT just like on my LCD's will show all the ground colors as shades of green in commando. Obviously this is incorrect as the red tnt is missing. correctable yes. 

 

So I guess what I'm asking just going off that one screen shot as a reference. Are the following correct

High Score - Bright Purple

Main Character clothes - Blue

Legs of Helicopter- dull purple 

Ground- Brown & Green

 

[youxia]

You're heading down a rabbit hole. I don't know about 7800, but NES for example does not have a "correct" palette due to how its internals work: it'd be slightly different on every unit, and then TV, which is why modern emus & FPGAs have multiple palettes to choose from.

 

If you have an original 7800 and an original 91' CRT then I'd simply assume that the correct colour is the one displayed. That's of course unless the TV is busted, or its OSD settings are in some extreme positions, but you can verify it by checking vs some more modern machine like SNES.

[oakcitycomics]

24 minutes ago, youxia said:

You're heading down a rabbit hole. I don't know about 7800, but NES for example does not have a "correct" palette due to how its internals work: it'd be slightly different on every unit, and then TV, which is why modern emus & FPGAs have multiple palettes to choose from.

 

If you have an original 7800 and an original 91' CRT then I'd simply assume that the correct colour is the one displayed. That's of course unless the TV is busted, or its OSD settings are in some extreme positions, but you can verify it by checking vs some more modern machine like SNES.

Well that's the kicker on this old set. All video values were set to 100 out of the box. So colors were all over exposed. This TV will be strictly used for the 7800 as my only other RF system (NES) has been RGB mudded.  Now that I've done a recap on the TV set I want to get the colors as close as possible with in reason of course to their intended display values. This is why I'm trying to find a some what color arcuate reference point. 

[+DrVenkman]

If you have a Concerto, DragonFly, Mateos or other flash cart, you can load up a copy of the 7800 Utility Cart and calibrate based on the color bar test screen. Commando on my own Toshiba CRT looks great. This is through composite (UAV mod I installed). 

 

 

[youxia]

Are these trees really pink?

 

Photographing CRTs can be a right ol' 'mare

[+DrVenkman]

1 hour ago, youxia said:

Are these trees really pink?

 

Photographing CRTs can be a right ol' 'mare

Nah, camera processing and weird room lighting. To the eye they look more or less like the emulator photo just without the artificially boosted saturation you seen from an emulator versus a real phosphor display. 

[youxia]

26 minutes ago, DrVenkman said:

Nah, camera processing and weird room lighting.

It's the bane of me.

 

 

[+x=usr(1536)]

2 hours ago, oakcitycomics said:

Well that's the kicker on this old set. All video values were set to 100 out of the box. So colors were all over exposed.

That makes me suspicious of the TV right off the bat.  In my experience, finding settings pegged like that usually indicates a problem with whatever picture component that setting adjusts.

 

Try this: give it a factory reset if you haven't already.  Also make sure that it's set for home use, not store display - a 1991-era TV may be a little early for that, but it can't hurt to check.

 

Next: attach a video recorder, DVD player (preferable), or other 480i device to its RF input and play back a good-quality recording.  Adjust the picture until everything looks natural to you.

 

At this point, you can replace <insert RF-based media source here> with the 7800 and have a visual baseline to compare against.  Trying to figure it out from controls that were cranked to 11 as opposed to what looks right to begin with is going to be a frustrating exercise.

 

2 hours ago, oakcitycomics said:

This TV will be strictly used for the 7800 as my only other RF system (NES) has been RGB mudded.  Now that I've done a recap on the TV set I want to get the colors as close as possible with in reason of course to their intended display values. This is why I'm trying to find a some what color arcuate reference point. 

 

Go with what your eyes and brain say look best for a movie, then take it from there

[Geoff Oltmans]

6 hours ago, oakcitycomics said:

My main objective is color accuracy not so much as the tone of the color. For example the 7800 on the newer Toshiba CRT just like on my LCD's will show all the ground colors as shades of green in commando. Obviously this is incorrect as the red tnt is missing. correctable yes. 

 

So I guess what I'm asking just going off that one screen shot as a reference. Are the following correct

High Score - Bright Purple

Main Character clothes - Blue

Legs of Helicopter- dull purple 

Ground- Brown & Green

 

Heh, if you're looking for accurate color you're using the wrong system here!  Colors drift over time after powering the system on.

[oakcitycomics]

8 hours ago, DrVenkman said:

If you have a Concerto, DragonFly, Mateos or other flash cart, you can load up a copy of the 7800 Utility Cart and calibrate based on the color bar test screen. Commando on my own Toshiba CRT looks great. This is through composite (UAV mod I installed). 

 

 

I do have a Dragonfly so will try and track down the 7800 Utility cart rom.  

[oakcitycomics]

6 hours ago, x=usr(1536) said:

That makes me suspicious of the TV right off the bat.  In my experience, finding settings pegged like that usually indicates a problem with whatever picture component that setting adjusts.

 

Try this: give it a factory reset if you haven't already.  Also make sure that it's set for home use, not store display - a 1991-era TV may be a little early for that, but it can't hurt to check.

 

Next: attach a video recorder, DVD player (preferable), or other 480i device to its RF input and play back a good-quality recording.  Adjust the picture until everything looks natural to you.

 

At this point, you can replace <insert RF-based media source here> with the 7800 and have a visual baseline to compare against.  Trying to figure it out from controls that were cranked to 11 as opposed to what looks right to begin with is going to be a frustrating exercise.

 

 

Go with what your eyes and brain say look best for a movie, then take it from there

This tv is to old for advance OSD. You pretty much just have color, tent, brightness, contrast, and sharpness. I've got it set to a nice image but I want to make sure that the colors are some what correct. Example if something is suppose to be blue I want it to be blue vs purple etc  

[+DrVenkman]

1 minute ago, oakcitycomics said:

I do have a Dragonfly so will try and track down the 7800 Utility cart rom.  

It's in @Trebor's Pro Pack. Do a search of the 7800 forum and you'll find it. 

 

That said, my iPhone XS camera *really* hates green from my CRT. This is the closest I can come to what my eyeballs see, but it's still too much "blue spruce" and not enough "green summer grass". I had to edit the photos in my phone to approximate the green I see IRL. These are both S-video. 

 

[Keatah]

11 hours ago, Geoff Oltmans said:

Heh, if you're looking for accurate color you're using the wrong system here!  Colors drift over time after powering the system on.

Not only does the console drift, so will the CRT's circuitry. And both are over 20 years old. Neither was built to any discerning standard.

 

The best you can do it look at screenshots and adjust to what looks right for you. And what feels right. And what you (or others) may remember. And then keep on top of it throughout the forthcoming years.

[Keatah]

8 hours ago, oakcitycomics said:

This tv is to old for advance OSD. You pretty much just have color, tent, brightness, contrast, and sharpness. I've got it set to a nice image but I want to make sure that the colors are some what correct. Example if something is suppose to be blue I want it to be blue vs purple etc  

Yes I know how that goes.

 

When I first got into videogames in the 70's I played Video Pinball on the VCS. I clearly remember the vibrant pure blue of the playfield. It's how my Zenith Chromacolor was set. And it rendered the baseball field of a real baseball game just perfectly. 

 

But fast-forward to the 1990's and the introduction of emulator Stella. Color was finally on its way to becoming stable and consistent. If not accurate. Yet.

 

I found that on one of my cheap-ass 6-bit vintage LCDs I have to adjust Stella's HUE slider down by 2 to 4 points (scale of 100) to get the deep vibrant blue. Just a couple of points, otherwise it renders as purple. A very visible and unappealing change - fixed by the tiniest tweak.

 

On my high end stuff I don't have to adjust anything.

[Jinks]

I found you need to play with your tv settings more than the console. I never touched any consoles colour adjustments like everyone keeps mentioning. Yeah the colour changes when it warms up.. So?? Set your tv to how you like it when everything is warm and forget about colour charts and maps etc. Who cares the colour police will not stop you. Live on the edge!

 

 

[+DrVenkman]

9 minutes ago, Jinks said:

I never touched any consoles colour adjustments like everyone keeps mentioning. Yeah the colour changes when it warms up.. So?? Set your tv to how you like it when everything is warm and forget about colour charts and maps etc. Who cares the colour police will not stop you. Live on the edge!

 

So … that’s fine but it won’t give you good results. Let your CRT and console warm up, then boot a color bar program. Use that to get your 7800 right, the. adjust your TV after that if necessary. The 7800 Utility Cart has a color bar generator that includes a feature Atari had way back in the earliest A8 SALT Cartridges - a pair of color blocks that SHOULD be the same. You adjust the color pot of a warmed up system to match these and your 7800 will be golden. After that, your TV variables can be dealt with separately. 

 

[R.Cade]

The 7800 is tough because of the two video chips and the odd color choices of some games (to me).

 

I did a composite mod on mine, and I can't get the 2600 side to have the same tint as a 2600 Jr. It just always seems a little "off". The 7800 I can make one game look good, but then another will be odd. Brown instead of green, and vice versa...

 

[youxia]

Extreme tweaking might be useful if you plan on using just one console. Otherwise, it's quite probable that the moment you connect some other source it'll require other settings and you'll have to adjust it all over again.

 

That's why I called it a rabbit hole earlier. I used to agonise about geometry, colour, convergence, etc, until the day when I realised that I spend more time with my nose 5 cm from the screen, chasing some non-existent ideal instead of playing games and enjoying this awesome ancient tech.

[oakcitycomics]

7 hours ago, youxia said:

Extreme tweaking might be useful if you plan on using just one console. Otherwise, it's quite probable that the moment you connect some other source it'll require other settings and you'll have to adjust it all over again.

 

That's why I called it a rabbit hole earlier. I used to agonise about geometry, colour, convergence, etc, until the day when I realised that I spend more time with my nose 5 cm from the screen, chasing some non-existent ideal instead of playing games and enjoying this awesome ancient tech.

This set will be specific to the 7800 only as all my other systems are feeding out RGB

[oakcitycomics]

8 hours ago, DrVenkman said:

So … that’s fine but it won’t give you good results. Let your CRT and console warm up, then boot a color bar program. Use that to get your 7800 right, the. adjust your TV after that if necessary. The 7800 Utility Cart has a color bar generator that includes a feature Atari had way back in the earliest A8 SALT Cartridges - a pair of color blocks that SHOULD be the same. You adjust the color pot of a warmed up system to match these and your 7800 will be golden. After that, your TV variables can be dealt with separately. 

 

Will be trying out the 7800 Utility later tonight. I always let crts and systems warm up before mucking around with image quality. At the moment I have it fairly close to the photo in the first post. Before hand it was displaying the dirty more reddish and the high score was more of a pink then a purple.  So getting close to where I think it should be 

Edited February 12, 2021 by oakcitycomics

[Trebor]

On 2/10/2021 at 10:00 PM, oakcitycomics said:

How accurate are the colors on the stock photos here on Atari Age.

Unfortunately, they are not very accurate for several details.  They are based upon the ProSystem emulator default palette which looks like this when viewed through a color chart:

 

 

Looks like it was shooting for a NTSC hot system palette but what is shown is impossible.   The gamma and saturation levels are all over the place. The hue values are not attainable with the combinations shown.

 

A more realistic color palette simulating a NTSC hot console would look something more like this:

 

 

However, there are artifacts, fringing, bloom effect, scanline intensity, and other items present under an RF and Composite output display that is absent from an RGB approximation.  S-Video, while removing many of the aforementioned items, is still not the same as RGB either.

 

The color dial inside the console adjusts the difference in degrees between the row of hues shown.  It is not, and does not work, the same as a display hue(tint) adjustment for a display.  Typically, when the console is 'cold' the value is around 24 degrees. When completely 'hot', around 28 degrees. 

 

Factory setting (Set within the first couple of minutes of a cold console being powered on) is ~25.7 degrees. It sets Hue $1x (The first strip of colors after the grayscale), to the same appearance and values of Hue $15x (the last strip of colors):

 

 

This appearance and setting will change though as the console warms up, depending when set, the average increase variance is somewhere around 1 or 2 degrees.  While most colors remain extremely similar if not identical to the human eye, the most drastic change occurs with the last two rows of color - Row Hue 14 $Ex and Row Hue 15 $Fx.

 

@DrVenkman capture is my personal choice as far as setting the color dial (~26.7 degrees).  It demonstrates the full 256 color palette of the system.  As far as an RGB conversion, it appears along these lines:

 

 

More about the 7800 palette can be read about on http://7800.8bitdev.org/ the Color Documentation section.

 

Check out the 7800 High Score Club for a wide range of captures, much relying on a person's personal preference/display settings.

 

Here's some links to various shots of Commando running on real hardware:

 

Commando 1

Commando 2

Commando 3

Commando 4

 

On 2/12/2021 at 4:20 PM, oakcitycomics said:

 So getting close to where I think it should be 

The best thing you can do.  It may be prudent not to try matching anyone else's particular setup.  There's a reasonable approximation to start with as far as the color palette, but in the end much of this comes down to personal preference.  Get the palette to where you think it should be and you are happiest with as far as the end results.