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Workflow for matching colors on this map?

map help.jpg

Hi! Thanks in advance for any advice you can give. This is a composite satellite image from google maps. The actual size is about nine feet tall at 300 dpi. It's going to be shown at an exhibition at my school as the background for some photos I took at various locations in this area. I'm planning to desaturate and maybe lighten it some to make the photos pop.

So, my question is about the differently-shaded boxes you can see there. They're artifacts of the satellite imagery from google--I guess those sections of the map were photographed at different times of year. I think they're distracting, though, so I'm trying to blend them into the rest of the map, or vice-versa. I've tried messing with the saturation of selected areas, but that is not working. I've also tried selecting certain colors in different areas and changing them individually, but I think I'm doing something wrong with that process. Regardless, I'm not even sure whether that will work. It doesn't have to be perfect...I feel like if the colors are a little inconsistent, it will be okay, but the sharp lines need to go.

Any advice?
...I'm planning to desaturate...
This is a good move and should be the first thing you do.

You'll find it much, much easier to blend a greyscale image than a colour one....you've only 256 shades of grey to deal with!

...It doesn't have to be perfect...
This is also good. You should get a good enough result in a reasonable time, so much so that if you didn't tell anyone they wouldn't notice.

...I feel like if the colors are a little inconsistent, it will be okay, but the sharp lines need to go...
You won't have to worry about colours if it's greyscale.

Here I did some of it using a levels adjustment for one area and a black 'Colour Overlay' layer style for another...


There are many ways you can adjust the image when its a greyscale, just use whichever suits the area you are working on.

Of course if you look closely you will see the edges but of course you have the advantage of knowing where they 'were' and that there was anything different in the first place.

It sounds as if you already do this but just do one small 'chunk' at a time...you can start bigger but one adjustment may not be correct for all the area, (see the top right adjustment...just not quite right for all of it)...so use masks as well...anything to make it easier. Your larger image will also be easier to work with.

After each 'area' stamp the visible layers and then start again with another area. Before long you'll be done in no time.


Thank you so much for your kind and detailed reply. I wasn't actually planning on desaturating completely, although that hadn't occurred to me--I'll think about it. I feel like a little color would probably help the viewer get a sense of place, but maybe I should just put the place names on there in color...hmm. Anyway, I will see if
first desaturating the whole thing somewhat makes it easier to get things to match.

Thanks :)

To expand a bit on the excellent advice MrToM gave, I would break up the image into a luminosity component (ie, a layer whose blending mode is luminosity), and then, above that, a color component (ie, a layer above the previous one, whose blending mode is set to color).

This will allow you to work separately on getting the luminosity and the color components in the oddball areas of the map to blend with the luminosity and color components in nearby areas of the "normal" parts of the image. Once you are done with the blending tasks, because of the way you constructed the layers, the luminosity and color components should merge back together to give you a nice, well blended color image.

As MrToM said, you should think seriously about individually blending several relatively small areas instead of trying to blend all of the oddball areas with their surroundings at one time.

With respect to blending the luminosity component, I would look at a histogram of the unaffected areas and use them in a masked levels adjustment layer to set the black and white points of the "oddball" areas of the image. Then, in a separate curves adjustment layer, adjust the curve so the histogram of the adjusted oddball area matches that of the "normal", nearby areas of the map. Making only these three adjustments (ie, black point, white point, and a curve for the mid tones) should get you very, very close to a perfect match for the luminosity component.

An analogous procedure can be used to match the color components of the oddball areas to their surroundings.


Tom Mann
(not to be confused with MrToM, LOL)
PS - Welcome to PSG. BTW, we're neighbors! I live in the 'burbs just north of the city and taught the senior thesis design course at one of the major nearby universities for 12 years before I retired.


Tom M