12 replies to this topic

[Textularia]

Dear List Members,

With papers being published at work and in an outside journal, I have a problem with choosing the colors for the polygons of geologic maps, which in my figures. In each case there is a printed and PDF version of the publication. At this time, I am only allowed to submit one version of each figure for publication. The problem is that the PDF version is in color, while the printed version is in grayscale. Thus, the colors, which I choose for the colored PDF version must also be distinguishable and look good when they are converted to grayscale print version.

Does anyone have any advice about how to choose colors, patterns, or combinations of both, which look nice in color but also contrast with each other as to be readily distinguishable in grayscale?

Are there any web pages, papers, or books that would help me with this problem?

Yours,

Paul Heinrich
Baton Rouge, LA 70803

[benbakelaar]

My cartography teacher always told us we should use no more than 4 shades of gray in a map. So you get black/white, and then 20%, 40%, 60%, 80%. I think some people would even say only use 3 greys + b/w, that being 25%, 50%, and 75%.

But that was advice for a map prior to its creation. Since you already have the maps created, I'm not sure if this works for you.

[Hans van der Maarel]

I'd have to agree with Ben here. When you're limited to grayscale, there's not that much you can do. 3 or 4 shades of gray and that's it. In fact, I'm not too sure on the 80% grey, it'd probabely be too much to black.

Of course this may not be an issue for your map.

If you want to show more different types of areas (or don't want to use the really dark shades of gray), you'll have to resort to a combination of grays and pattern fills.

[David T]

I'd have to agree with Ben here. When you're limited to grayscale, there's not that much you can do. 3 or 4 shades of gray and that's it. In fact, I'm not too sure on the 80% grey, it'd probabely be too much to black.

Of course this may not be an issue for your map.

If you want to show more different types of areas (or don't want to use the really dark shades of gray), you'll have to resort to a combination of grays and pattern fills.

<{POST_SNAPBACK}>

I was just looking through Cynthia Brewer's "Designing Better Maps" book yesterday, looking at some color techniques. I noticed in there that she does show a gray scale that incorporates 9 different shades.

Personally, I wouldn't recommend more than 5 if possible. 6 if necessary.

If you follow Ms. Brewer's techniques, here are her recommendations:

5: 3, 20, 41, 61, 85
6: 3, 15, 26, 41, 61, 85

[benbakelaar]

5:  3, 20, 41, 61, 85
6:  3, 15, 26, 41, 61, 85

<{POST_SNAPBACK}>

In this case are you excluding black (100) and white (0) as classes?

[ELeFevre]

Here is another handy quote to remember... from Cynthia Brewer's " Designing Better Maps" "Equal percentage steps do not equal visual steps."

I would stick with 4-5 classes and start at 2-3% black as well.

[Nick Springer]

5:  3, 20, 41, 61, 85
6:  3, 15, 26, 41, 61, 85

<{POST_SNAPBACK}>

In this case are you excluding black (100) and white (0) as classes?

<{POST_SNAPBACK}>

3% and 85% are effectively white and black when printed.

[Hans van der Maarel]

It all depends on the actual map. If you print them right next to eachother, so that the areas actually touch, 85% grey and full black can be distinguished (assuming it's a high-quality print of course). If you print them some distance apart, it's going to be much harder, if not impossible.

[peanut]

My two cents...

Many years ago in a cartography class the professor talked at length about the lighter shades of gray being more distinguishable than the darker shades of gray. This has sort of stuck with me so I usually do something like this when making grayscale maps:

5: 0, 10, 30, 50, 85
6: 0, 10, 25, 40, 60, 85

I don't find shades of gray over 80% to be distinguishable at all especially in print.

Rich

[gorillamap]

As far as colors that work well as grayscale, I haven't found any helpful resources. I run into a similar problem with my maps, which are constantly being photocopied and faxed. I've just done a lot of trial and error by Xeroxing the printed version to ensure everything still shows up. So far I've learned that subtlty does not work and contrast is king.

You may want to do the same experimenting by converting your maps into grayscale through Photoshop.

Mike

Mike Pesses
Grad Student | CSUN
GIS Specialist | County of Kern

[natcase]

Also bear in mind the printing method: if you are printing offseet with an average printer, any light tints (like the 3%) Cindy Brewer suggests, will effectively pring much darker because of dot gain... probably actually more like 8-10% of the actual page will be inked.

Likewise, laser printers, especially if you are using a fine dot screen (133 lines per inch or more), will not produce 100 different screens. For every "cell" in qhich a dot is placed, there may not be 100 pixels of toner available to toggle on or off. For a test, produce a smooth gradation across a page, say from 0 to 50%, and count how many bands there are. This will tell you how many percentages you actually have available to you for the dot-screen density at which you are printing.

Nat Case
Hedberg Maps
Minneapolis

[nedmohr]

Hi,
you may be interested in some research done over at Northwestern university:
http://www.cs.northw...820/color2gray/
They developed some code to minimize the information loss in the color to grayscale transformation.
cheers
ned

[l.jegou]

Thanks, Nedmohr, that's very interesting !