Better colour control for Toolbox gadgets

Yes it is.

I meant as in not existing in the documented sense, not as in the X-SWI sense. This is perhaps the first time you’ve talked about the API.

You’ve got the wrong end of a very long stick.

Not the first time. 😉

They aren’t gamma tables.

They are documented as “gamma correction tables”. What would you call them? I ask because if they aren’t gamma then they shouldn’t be called that. The documentation needs to be changed in that case.

You’ll love this: https://www.riscosopen.org/wiki/documentation/show/GraphicsV%20palette%20colours

so the non-linearity of the LUT makes the pixel values linear, if done correctly

As an aside, am I right in remembering that the VIDC had some real weirdness with it’s LUT? I’m probably thinking VIDC1 (which might explain the 64+tints nonsense).

I’m not sure what “the OS” means

Baked into the ROM or part of the Boot as typically supplied (by ROOL or third parties like Direct) – widest exposure, “people will just have it”.

Technically it’s a LUT. Whether it’s doing something with your gamma or changing everything to mauve depends on the values in it, so to claim it’s always a “gamma table” is not conducive to a firm grip of either end of the stick. “Transfer curve” is safer.

If you had said “pass the components through the LUT to get values that are definitely 2.2 gamma” you would at least have been wrong in the right direction. But suggesting that the LUT gives you a linear result (which can then be used to calculate luminance) is extra wrong, IYSWIM.

VIDC1 only had 16 palette entries, hence the “standard 256 colour palette” that amongst other things led to Archimedes machines having a different gamma again from every other machine on the planet (due to an elevated black level):

Left: How 256 colours looks on a modern monitor
Right: How it looked on a correctly adjusted CRT monitor in 1987

So VIDC1 didn’t have a LUT, just a 16-entry palette. VIDC20 had 256 entries. From a hardware point of view, the LUT and the palette are the same thing, but from an API point of view they’re separate (and with Monitor present, there’s a palette, the user LUT and the calibration LUT). In the Nucleus you had 8b palette entries, 8b user LUT, and 16b calibration LUT, which were combined into a 12b hardware LUT. That’s a lot of luts.

None of the monitors I had available in 87 to 94, adjusted quite that well, so as not to see the washout from the tints.

YMMV. I think I used my M128 colour monitor on the A310 and it was that good. Also note that NTSC monitors typically had a 5% higher black level than PAL.

We can work out the black level required for this to work. The “standard palette” was designed for the 12b VIDC1, such that the top two bits of R,G,B could be specified, but the last two bits of the byte affected the next two bits of all three components – hence the white. So when going from dark red %0100 to the next true red %1000 the three intermediate shades also added green and blue, i.e. %0101 0001 0001, %0110 0010 0010, %0111 0011 0011. So this added 3/15 white before stepping to the next pure colour.

But if one elevated the black level to 3/15 then the small amount of green or blue would display as black, reducing the dynamic range but purifying the colours. The small increments to red were visible because red was already above that elevated black level. So black level needed to be at 3/15, or 200mV. Out of the box, PAL monitors were set to 0 and NTSC about 60mV. Whether the components in your monitor allowed black level to be set at 20% was dependent on manufacturer, batch, age, Tizer spillage and blind luck I think.

But no Arc gamer left their black level at zero.

Retro emulators ought to simulate this. My desktop conversion of the great Big Bang certainly does, with both 20% black level and gamma correction:

Big Bang

Your printer is way fancier than mine.

It’s just a photo printer. Epson make a range of photo printers that have 6 inks, as you see, presumably because they think they can get better colour rendering. The previous printer, that I’ve just taken out of service, is an Epson Stylus Photo RX620, which also has 6 inks.

Annoyingly, all their Ecotank printers seem to be only 4 inks. If they had made a 6-ink Ecotank, I’d probably have bought it.

The most surprising aspect to me of the new one is that the stack of ink cartridges is at right angles to the direction of travel of the print heads.

Annoyingly, all their Ecotank printers seem to be only 4 inks. If they had made a 6-ink Ecotank, I’d probably have bought it.

I have an Epson ET-8550 which is both Ecotank and has 6 inks. But not the 6 inks you are probably expecting, because 3 of them are variations of black.

Nine inks – those were the days

I’m sure I remember an Epson that used six different greys to produce astonishing B&W photos, but I can’t find it now.

When looking for an A3 photo printer, I also came across the Canon imagePROGRAF Pro-300 which has 10 ink tanks. But “only” 9 colours, because on tank has the “Chroma Optimizer” inside. Whatever that is…but I found it interesting that it comes with both “Photo Black” and “Matte Black”.

The Canon BJC7000/7100 used to have an “Optimiser” though it was built into the black ink tank, if I remember rightly. As I understood it, this was laid down on the paper ahead of any ink to make its own coated paper.

The most impressive inkjet I ever saw at IPEX had a solid white ink in addition to colours, so could print texture. I saw it print an oil painting complete with brush strokes, cloisonné with enamel fill, and woodgrain. It could print at some distance onto shaped objects, as large as a door.

I don’t think it made it to production, sadly.