How to print chrome silver as accurate as possible.

[deki]

Experiment with shades of gray for Mc Donald Douglas DC-3.

[John Dell]

The natural metal finish on airplanes is a subject open for interpretation. This is how I do it. Below are some parts from the Stratoliner and B-17G. I try to represent a commercial aircraft as being a lot shinier and cleaner than a combat aircraft such as the B-17G. I always find it interesting to see how different artists tackle this problem. Some techniques are quite convincing.

[ContourCraig]

I have been trying for a long time to replicate the colors found in photographs in print.
I used Corel Draw many years ago, but now GIMP 2.8 is open source and does everything pretty well. First locate a photo or drawing on the internet or scan, then take a screenshot 'saved to file'. Open this in GIMP.

For the purpose of this post I have taken a screenshot of AirDave's thunderbolt wing. Using the color picker tool, [CTRL B] pops up a toolbox. Select a region of a color you want to investigate. The selected color will appear at the bottom. Select the rectangle and the color information popup will appear.

Notice that the light 'green' aluminium color has RGB colors 191 198 191. For pure grey the values would be 191 191 191. Selecting a darker shade on the wing, the values are 137 143 140. The grey color values are also shown in the RGB sliders. (vertical row). For illustration 250 250 250 would be light grey and 5 5 5 very dark grey. Notice that the Saturation 's' is very low for grey colours (4 in both cases). If you increase the saturation the grey would turn green or blue repectively as indicated in the gradient information window,

With this information, you can analyse any effect you see in a picture/photo/painting/model.

Modeling purely sunlighting/shadow effects, is achieved by summing the RBG values.
E.g. 191+198+191= 580. Divide each value by this to obtain a fraction of 1. E.g. 0.329 0.341 0.329. The lighting effect of shade and shadow alone can be recreated by multiplying each of these ratios by the same factor. Fiddle with the ratios if you want to include a relection of a different color. For example a reflection off a wingtip may include skyblue, while a reflection from a row of windows or insignia may include a hint of those colors in the basic grey tone. The grey for the lower bodies may include some slight ground brown/yellow (as well as the bigger grey shift for shadows under the wing).

[cfuruti]

Originally Posted by ContourCraig

I used Corel Draw many years ago, but now GIMP 2.8 is open source and does

Congratulations, but AFAIK GIMP has always been open source. And Inkscape is a better counterpart to Corel Draw.

Originally Posted by ContourCraig

Modeling purely sunlighting/shadow effects, is achieved by summing the RBG values.
E.g. 191+198+191= 580. Divide each value by this to obtain a fraction of 1. E.g. 0.329 0.341 0.329. The lighting effect of shade and shadow alone can be recreated by multiplying each of these ratios by the same factor. Fiddle with the ratios if you want to include a relection of a different color. For example a reflection off a wingtip may include skyblue, while a reflection from a row of windows or insignia may include a hint of those colors in the basic grey tone. The grey for the lower bodies may include some slight ground brown/yellow (as well as the bigger grey shift for shadows under the wing).

For slight and subtle color adjustments, it could be easier using the Curves dialog (Colors>Curves...). E.g., select the Blue channel and drag a point on the diagonal line; pull it up for a bluish tint, down for a golden one.
Colors>Levels... is simpler (e.g., select the Blue channel, in the Input chart move the white triangle to the left to enhance blue, move the black triangle to the right to enhance gold) but offers less (or maybe a different type of) control.

[aansorge]

GIMP has a filter (only GIMP calls this feature a filter, as far as I can tell) which can create a fill that looks like chrome. It is called Cool Metal. The rules on how to use it (the filter) have changed since I used it to create a chrome nameplate, but it seems that you must change the color of the skin (or whatever you want to treat) to the color alpha (normally this is transparent), you can then access the filter under 'Alpha to Logo.' It lets you pick colors for the gradients (blue sky above, green grass or brown dirt below), and adds a level of waviness.

https://docs.gimp.org/en/script-fu-c...ogo-alpha.html

Here is what we get for instructions.

[Burning Beard]

Military aircraft shouldn't be shiny. The surfaces were not polished to a high gloss because it made them to visible. They would naturally reflect a little light but it should not be consistent across multiple panels. Different panels may have been burnished coming out of the factory but if they where not attached to the plane with that in mind they would possibly reflect light in an entirely different direction.

My father told me that one of the jobs of ground crew for the B29 he flew was to clean off the exhaust residue because it caused increased drag if allowed to build up. So in that case you would have streaks from the fuel they used to clean the exhaust which would mess up any consistent reflection. Replacement panels would also reflect differently. So basically, if you are not building a model of a factory fresh plane, cut down the shine.

Beard