The Old Joel on Software Forum: Part 3 (of 5) - Why can't you print the color white?

Why can't you print the color white?

hilo
Saturday, October 25, 2003

You can. Some dye sublimation printers do.

Troy King
Saturday, October 25, 2003

hilo,

If you're really looking to do that, it will take some special hardware, as was mentioned previously. You'll need to talk to some people who specialize in that kind of thing though to find the printer. Ten years ago I could have told you who to talk to. Now, I'm clueless because I've been out of the field for so long. Look for your professional digital photographers and where they're going though. That's the crowd that uses these sorts of toys.

Clay Dowling
Saturday, October 25, 2003

I think at least part of the answer is that printers are generally CMYK devices, as opposed to RGB devices.

With RGB devices black is the total absence of color while white is created by adding all the colors at their highest values (e.g., R: 255, G: 255, B: 255). CRT and LCD monitors are examples of RGB devices. The creation of white is an "additive".

CMYK devices work the opposite way, in a sense. With these devices you can't create white by adding all the colors together, instead you end up with black. The process to get white is "subtractive"; you have to take all of the color channels at their minimum values (i.e., 0) to get white. Printers are generally CMYK devices, and what you're left with after you subtract out all color is just the blank (hopefully white) page.

Herbert Sitz
Saturday, October 25, 2003

Herbert explained it, so I'll just try and clarify.

Monitors, TVs, etc. are active devices that output light. The colors are additive, so that red light plus blue light plus green light (in an RGB colorspace) all combine to produce white light. Or, as ziplock bags taught us, yellow plus blue makes green.

Printed materials are reflective, and so work in a subtractive manner. A red ink, illuminated by white light, reflects the red colors and absorbs (subtracts) the other colors. Blue absorbs the reds and greens and reflects blue. Green, reflects the green. Put all three inks together and they absorb all the colors, reflecting no light -- giving black. Printers work in with a CMYK colorspace, so the inks produce Cyan, Magenta, Yellow, or Black (pre-mixed so you don't have to waste your CMY to get it).

You could print white: you just need an ink that reflects all the colors diffusely. And then print it on a non-white surface. Fundamentally, this is no different than painting a wall with white paint or using white-out.

I assume there's little call for white printer ink since most printing is on white paper.

David Fischer
Saturday, October 25, 2003

Thanks for the very informative replies. I always thought it would be cool to be able to print on black paper but it doesn't sound like that is possible without some expensive equipment.

hilo
Saturday, October 25, 2003

If you REALLY want to print white on black, try Kinkos or your local equivalent. The one's I've seen in S. FL. have some very high end printers that can probably get the job done. You'll have to pay a premium. TANSTAAFL.

Tom

Tom Dratler
Sunday, October 26, 2003

> Monitors, TVs, etc. are active devices that output light. The colors are additive, so that red light plus blue light plus green light (in an RGB colorspace) all combine to produce white light. Or, as ziplock bags taught us, yellow plus blue makes green.

But, ziplock bags are subtractive, not additive.

There is another way of looking at it. Imaging a cube. One vertex is labelled black, and the opposite vertex is labelled white. Starting from the black vertex one can reach three vertices via a single edge. These are the primary additive colours red, green and (dark) blue. Starting from the white one can reach three other vertices via a single edge. These are the primary subtractive colours yellow, cyan (light blue) and magenta (<> red). These primary subtractice colours are one step in the direction of the black vertex. Two more steps along other edges are always needed to get at the black vertex.

All colours in the colour cube can be described by providing three co-ordinates that tell how far to go in the x, y, and z directions. As our origin we can either take the black vertex or the white vertex. Another way to describe colour co-ordinates is based on polar co-ordinates: the colour-hue-saturation system.

Karel Thönissen
Sunday, October 26, 2003

Karel, you'd best stop smoking that stuff now if you want to be straight for work in a few hours...

Philo

Philo
Sunday, October 26, 2003

Care to provide arguments for your statement?

I re-read my posting, and apart from a number of small spelling errors it was mathematically correct.

Be careful when you post a comment like the one above, please.

Karel Thönissen
Sunday, October 26, 2003

"But, ziplock bags are subtractive, not additive."

Sorry, silly error.

Karel - can you restate your Cube explanation. The statement that from the black vertex you can reach three vertices from a single edge doesn't make sense. I see that you can reach three vertices along three different edges. And (I infer) those new vertices are the primary colors RGB. Then similarly for CMY. Is that what you meant?

(Color Theory is in my field but it's not my thing)

David Fischer
Sunday, October 26, 2003

Yes, all primary edges can be reached in a single step (via three different edges).

Karel Thönissen
Monday, October 27, 2003

Out of curiosity, is it technically possible to place a special int carteridge into a regular inkjet so that it can print white onto black paper?

Would the ink density be enough to cover the dark background?

Would a customer driver have to be written? Perhaps a bitmap could be treated to print correctly with the new ink carteridge?

Any ideas about how this could all be achieved by somebody with a modest budget and limited expertise?

Ged Byrne
Monday, October 27, 2003

Dear David,
As far as I undestand the post you have a cube with six faces. one white, the opposite black, one, red, one green, one blue and one yellow. Any edge of the cube will touch four faces, the two on either side, and the two at the top and bottom where it touches them with its point.

The red, green, blue and yellow faces are not uniformly coloured but go from dark to light according to whether they are nearer the black face or the white face.

I've no idea if this image is of any real value, but I believe it is what Karel is talking about.

Stephen Jones
Monday, October 27, 2003

Maybe Karel is referring to a vertex and not an edge.

Monday, October 27, 2003

You can make custom ink cartrages for ink jet printers to do all kinds of stuff.

You can fake around the print drivers with some creative coding.

Somebody made a cartrage for Epson printers that has 4 different shades of gray for really good black and white printing.

It's just hard and requires specific formulations of ink which may or may not be compatable with really *interesting* effects.

There's also using a printout to burn a silkscreen or etch lithographic plate and doing things that way -- which can be done by a motivated hobyist for not too much money for small-scale production.

Karel's explanation makes sense to me, but then I've seen it before.

Flamebait Sr.
Monday, October 27, 2003

Karel's explanation can be made a little more clear (no offense) by adding "each", a la

"Starting from the black vertex one can reach three vertices each via a single edge."

If we put black at (0,0,0) and white at (1,1,1), R, G, and B would be at, say, (1,0,0), (0,1,0), and (0,0,1) and C, M, and Y would be at, say, (0,1,1), (1,0,1), and (1,1,0). I probably don't have the right opposites there but I hope the description is otherwise clear.

Since we've covered all 8 vertices of the cube, it's also clear that either system can be used to describe any possible point in the cube.

Each face of the cube shows a 2D spectrum of colours.

http://www.morecrayons.com/palettes/webSmart/colorcube.php

shows a pretty good visualization.

Jody Woodland
Monday, October 27, 2003

christopher Hester
Tuesday, October 28, 2003