What's all this about colour?

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Stephen White
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What's all this about colour?

Post by Stephen White » Sat Jun 06, 2020 6:41 pm

Since I'm not about to create a social bubble on a Caribbean island this weekend, I thought I might write a few notes about colour. I've been working a lot recently with video editing software and if anybody knows and uses colour well, it's the photographic community. I've put together some notes about understanding colour and some modelling apps which might be useful. If this raises interest, it could find its way into a Knowledge Base topic. Here goes.

Colour is emotive. The British and Americans can’t even agree about how it’s spelt. Colour is also complicated. Colour provokes clear and strongly held opinions – which are generally “wrong”. In this case, “wrong” means over-simplified. If it’s easy to get “wrapped around the axle” about colour, is it also possible to keep it simple and yet be true to the original. Are there tools which both well grounded and, above all, useful to us as model makers? Read on.

The Problem with Colour

Colours are given descriptive names – light brown, olive drab, NATO Green and the classic: Dunkelgelb. There are two problems with this:

- The name might not cover all the variations. There were at least four official colours of Dunkelgelb and many more variations in the field after mixing and weathering.

- We all perceive colour differently. Our eyes and brains affect our perceptions, as do transmission devices such as photos, monitors, film etc. So trying to compare colours on a tablet or monitor is delusional, you’re not looking at the colour itself but a representation of it using a very limited palette.

-This leaves us with three choices:

- Don’t care – it’s only a model and if it looks about right, that’s good enough.

- Rely on someone else – if a supplier says it’s a “Real Colour”, that’s good enough. So called authentic paints vary a lot, some are close to the originals but others are way off. How can you reliably tell the difference, assuming you care about accuracy?

- Do it yourself, objectively. We need a reliable and accurate way of comparing colours and altering them. Read on:

How Colour Works

Colour is light, interpreted by our brains. Like any other waveform, light waves vary in frequency, amplitude and wavelength but enough of physics. We’re used to terms such as colours, tones, tints, shades. Those words are attempts to describe how a colour may vary. The problem is that you can’t measure them. Although an artist may not use the same terms as a photographer, there is a general agreement that colour has three qualities. Have a look at this picture:

Hue, Brightness, Saturation.jpg

If you take a red and add black or white, you make the paint look lighter or darker. These variations are commonly described as tints and shades but a better term for us is Brightness. Photographic editing software would call it Luminance but Brightness is easier to grasp.

Take the same red and add yellow you move the “colour” towards orange. These variations are changing the Hue or Chrominance (from the Greek Chroma – colour).

Finally, add grey to the red and the hue becomes less vibrant, less intense. This is changing the Saturation.

So we now have a language with which to describe and measure colour:

- Hue: where is it on the colour spectrum?

- Brightness: how light or dark?

- Saturation: how pure and intense is the colour?

There is a very simple and clear explanation of Hue, Brightness and Saturation here:

https://youtu.be/2pNW7wn3Y4k

Incidentally, you can explain how a model filter works using these terms. Mix enough colours together and you’ll eventually get grey ie totally desaturated colour. Filters desaturate a basecoat to dull it and blend different colours. Use it on camouflage and the colours become more unified and less stark. A filter can also change a hue or darken/lighten a hue.

We'll avoid the whole subject of primary, complementary and secondary colours because it’s a minefield and not terribly useful to us. We really only need to know something about whether one “colour” matches another (is this model paint an accurate representation of the original) and how we alter paint (how do we make it lighter, less intense, vary the hue). This incidentally is one very strong reason for using oils for weathering. Since they are infinitely mixable and translucent, with oils you can easily vary hue, brightness and saturation, which is not easy with acrylics or enamels.

What was the Original Colour?

If you want an accurately coloured model, you have to know what colour the original was. This is a huge subject which has kept anoraks busy for years. Fortunately, military authorities tend to be very strict about paint specifications. They use international colour matching standards to specify paint qualities in order that paint suppliers produce consistent and reliable products. This incidentally is one of the pitfalls of German WW2 colours, because as the war progressed, paints were increasingly unreliable and variable in application after being mixed by diluting a paste.

There are three standards relevant to us:

- RAL. RAL stands for Reichs-Ausschuß für Lieferbedingungen. Set up in 1927, the RAL maintains the German standard colour system. Colours are described using a four digit code, eg RAL 7028 Dunkelgelb. You need to know though that the colour charts we see today are a post war system, which eliminated some of the wartime colours. The wartime standard was RAL 840R. For that reason, RAL has to be used with care.

- BS381c. The British Standards Institute system is pretty universal and was used to specify WW2 military colours. The WW2 standard was BS987 but most of the colours have equivalents in the modern standard chart, BS381c. There are many conversion charts available online.

- FS595. The US Federal Standard 595 has its origins in the problems the US government had in obtaining consistent colors for military equipment.

How do I compare the original colour with a modern paint?

These standards provide colour charts which describe a catalogue of individual colours. To compare colours you need a tool which describes the whole continuous colour spectrum, known as a colour space. This is inevitably another minefield. There are colour spaces for print, for digital use and very sophisticated systems which take into account hue, brightness and saturation and mimic the colour receptors in the human eye. An example colour space is here:

Screenshot 2020-06-06 at 11.59.57.png


Again, enough science.

All we need to know is that these systems ascribe three values to describe a specific colour and one of them, CIE 1931, takes into account luminance and chrominance.

Other systems in common use such as sRGB (optimised for digital use), CMYK (for print use) and Munsell also use a set of three values which describe a mix of the primary colours, whether those are red, green and blue or cyano, magenta, yellow and black.

There’s no real need to understand what the three values mean because we’re only going to use them for comparison. We first need some tools to help us. This is where I need to introduce a really useful online resource:

https://www.e-paint.co.uk

This website has all the common colour standards and gives descriptive values for each colour in all the main colour notations. Once you’ve got a description of the original colour, you have a means of comparing it with modern paints.

Take NATO Green for example, one of the colours used on Chieftain camouflage. NATO Green is a BS381c colour:

Screenshot 2020-06-06 at 12.23.40.jpg

E-paint will then give you useful information about colour values, which you can use in other programs to compare colours and, in another page, conversions to other colour standards:

Screenshot 2020-06-06 at 12.25.43.jpg

I’ve highlighted the values in CIE L* a* b* and sRGB. E-paint also gives close matches in other colour standards. This is useful because model paint manufacturers use different standards. Vallejo for example quotes FS595 values for their paints and mixes to achieve historic colours. See their useful conversion chart here:

https://acrylicosvallejo.com/wp-content ... colors.pdf


Screenshot 2020-06-06 at 11.42.49.jpg


Now for the punch line: someone has done all the hard work for us. There are two apps which allow us to:

- Compare original colours with modern model paints

- Make up accurate colour mixes if a model paint isn’t available

- Specify original colours in a language which commercial paint mixers can use

iModelKit:

Screenshot 2020-06-06 at 12.36.49.jpg

https://youtu.be/ofjEns6Q2bw

iColorKit:


Screenshot 2020-06-06 at 12.41.55.jpg


I won’t go into using the two apps because they’re self-explanatory but here are a couple of examples of use:

Example One – how do I paint a Chieftain in Berlin Armoured Squadron Urban Camouflage?

- What were the original official colours? Using Dick Taylor’s Warpaint, Volume 3, we establish that the original colours were White, Dark Admiralty Grey (to BS381C 632) and Service Brown (to BS381C 499)

- Who makes an accurate Dark Admiralty Grey? Using iModelKit, we can find a match. We select the BS381c colour palette from the paints menu and get a chart of possible matches:

IMG_3598.jpg

We can see that Tamiya XF77 is a match, as is Vallejo 70.992. To check this, we can tap on the calculator icons to give us a direct measure of how good the match is, using the CIE notation. (Any figure Delta figure under 10 is a close match, any under 1 is undistinguishable to the naked eye).

IMG_3599.jpg
IMG_3600.jpg

We can see that Tamiya XF77 is an excellent match. The Vallejo colour is close and you could use the iModelKit paint mixer to work out an exact match. Let’s do that with the third Berlin colour, Service Brown.

Service Brown is BS381c 499. We select this in the top section (Choose Reference). We then tap on + New Paint. The app asks us to choose a paint type. Sticking with Tamiya, we get a list of colours, in descending order of match. Against each is a measure of how close the match is, in CIE notation. We add XF84:

IMG_3601.jpg

We see that the overall match has a delta of 8.46 and that we particularly need more green (delta of -20). Tap on + new paint and select the top paint, Tamiya XF54 and now the match is closer, delta 5.87 but now we have too much blue (+9).

IMG_3602.jpg


Three colours is about the maximum you would want for a mix but by adding XF72 we get a delta of 3.82, which is close. Note the arrows on the side.

Picture 1.jpg

These allow you to vary the proportions of paint, which up to now have been equal measures. It’s worth playing around with these. Better still, press the calculator icon and the app will select the best match for you. In this case, if we now double the proportion of XF54, we get an almost perfect match. Result. The final mix is two parts XF54 to one part each of XF84 and XF72.We might have found that there are easier mixes using a different manufacturer’s products but this example shows the power of this tool.

Example Two - Is AK753 an accurate match for Dunkelgelb (Initial)?

I’ve cautioned about the inaccuracies of digital representations but there is one tool in both apps which, if used with caution, can be useful. It’s the colour picker, linked to your tablet or phone camera. The apps will allow you to use a photo of a colour chip to establish the colour notation for that colour. If, for example, you have an authoritative colour chip, this can be a way of checking the accuracy of a so called authentic model colour, using the colour comparison tool in iColorKit. You could use the colour picker photo tool to compare an authentic chip with a sample of model paint. You have to be careful to avoid artificial light and photograph both colours in the same light.

AK-Interactive offer a range of colours based on originals. We can compare AK753 Dunkelgelb (Initial) with the equivalent colour chip presented by the widely respected source Tomas Chory.

Screenshot 2020-06-06 at 17.44.37.jpg

From iModelKit, we establish a description of AK753 in CIE notation.

IMG_3604.jpg

We then use the colour picker camera in the Compare Tool in iColorKit:

IMG_3603.jpg

Entering the two values into the compare tool, we get a not unsurprising result, which is that the colours are not a good match:

IMG_3606.jpg


Of course, we could then use the colour mix tool in iModelKit to refine the colour but a better option might be to find an alternative model paint. This method has to be used with caution but can be a useful check.

So does any of this matter? Some modellers don’t much care about accuracy of colours and for others, there is a ready made let out which is that colours of AFVs on operations are affected by so many other factors that spending a lot of effort to get an historically accurate basecoat is seen as a waste of time. For others, it’s worth putting in some effort to create an authentic replica of the real thing, the essence of scale modelling.

As I said at the beginning, colour is a minefield of complex physics, passionately held prejudices and impenetrable and contradictory terminology. If this guide has offered any tools which are actually useful, it will be worthwhile.
Last edited by Stephen White on Thu Jun 11, 2020 1:46 pm, edited 1 time in total.

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Stephen White
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Re: What's all this about colour?

Post by Stephen White » Sun Jun 07, 2020 10:52 am

I should add that the two apps, iModelKit and iColorKit only support iOS, not Mac OS or Windows. Pity really because they're so useful. I've not found anything similar for PC platforms. If anyone does come across a useful app, it would be good to share here.

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Re: What's all this about colour?

Post by Kevin Hunter » Sun Jun 07, 2020 11:31 am

An interesting post Stephen, even though writing it may have been a poor substitute for basking on your Caribbean beach.

I'm not an accomplished modeller by any stretch of the imagination, and would probably (definitely) put myself in the "rely on someone else" category. Most definitely not "don't care" otherwise we might end up with another pink Chieftain (although as we know there is evidence that this could still have been a factually correct model).

So far I've relied on BS381 colours produced in rattle cans but, for my Quad, I struggled to find the Khaki Green No.3 that I wanted. I have recently taken the plunge and delved into airbrush territory and have been using AK "Real Colours". These have apparently been developed in collaboration with Mike Starmer, amongst others, which (to me) should make them "reliable" in keeping with my approach to these things.

For reassurance (while heeding your cautions) I thought it would be interesting to compare the AK paint to Mike's colour chip in his camouflage books - but iModelKit doesn't include the "real colour" range. Furthermore, reference your comment on operating platforms, it seems that iColorKit wont even work on iPad - only the iPhone. :(

I use a windows based PC and an Android telephone. We really could use a multi platform version of these apps in order to make them universally helpful.

Kevin

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Re: What's all this about colour?

Post by Adrian Harris » Sun Jun 07, 2020 11:39 am

Thank you Stephen, an interesting read.

If I may say so, I've always understood that colour, as perceived by the human eye/brain, is the absence of light.

At each end of the scale, something which absorbs all light will appear black and something which absorbs no light will appear white.
Something which absorbs all the red and green light will appear blue. Etcetera, etcetera...

This is important as the perceived colour of an object is affected by the colour of the light which is incident on the surface.

The Dunkelgelb which looks perfect in your 4000K LED lit workshop will look different in daylight and possibly dreadful under the sodium lamps of the Tank Museum. It is also affected by the colour of the surroundings. Olive Drab is said to be brown when next to something green and green when next to something brown.

The Mike Starmer mix for British Khaki Green No 3, as used on vehicles such as the Quad, is given as combination of three Revell acrylic colours in the ratio of 12:5:7. You know when you get to double figures that someone has spent hours working that one out :shock:

Another mix given on HMVF for KG No 3 is "3 x RAL 6014 to 1 x RAL 8001". Mixing from a German colour palette to get an undocumented British colour tickles me somehow.

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Re: What's all this about colour?

Post by Stephen White » Sun Jun 07, 2020 12:20 pm

Thanks for the feedback.

Kevin, I can confirm both apps do work on an iPad. I took the screenshots in the post on my iPad.

Re AK and British Khaki Green No 3. (Health warning - printed media). I have Mike's colour chips and thought I'd compare his Khaki Green with the colour chips in the AK Book, Real Colours. Interesting result (notwithstanding that the Real Colour chips are printed and may therefore not be representative of the paint AK sells). The match came out as Moderate, which is probably a good result. Top figure is Starmer, bottom is AK:

IMG_3608.jpg

This is a comparison with the colour swatch on the AK website (Khaki Green No 3 bottom):

IMG_3610.jpg

Again, a moderate match, which is under 10 and therefore probably close enough.

I've seen people having some reservations about the AK Real Colour range but at least they are trying hard to be authentic. For aircraft, I've seen great praise for the Mr Paint products. I've just used them for a Fairey Barracuda model I've just made for the Fleet Air Arm Barracuda restoration project and I'm full of praise. The colours are smack on (as measured) and they spray beautifully. I get them direct from source. They do a British Khaki Green No 3:

https://mrpaint.sk/index.php?route=prod ... uct_id=465


Adrian, yes absolutely re additive and subtractive models, as I said I tried to avoid getting drawn into the physics which can be mind blowingly complex, at least for my small brain. The point though about colour perception being strongly influenced by incidentally lighting is important. There are some great conversion charts such as by IPMS Stockholm, if anyone needs to convert paint mixes but iModelKit does the job brilliantly and keeps its charts up to date.

Glad this is of interest.

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Re: What's all this about colour?

Post by Kevin Hunter » Sun Jun 07, 2020 12:50 pm

Stephen White wrote:
Sun Jun 07, 2020 12:20 pm
Kevin, I can confirm both apps do work on an iPad. I took the screenshots in the post on my iPad.
Intriguing - your own screen print for iColor shows a statement that it is only available on app store for iphone. Using my (dated) iPad Air, iColor is not showing in App store - but iModel is. It may be a limitation on the version of ios. Despite being fully up to date my ipad doesn't get the same OS as newer models, as Apple encourage users to upgrade hardware.

Thanks for the comparison on AK khaki Green, disclaimers accepted. I'll certainly take a look at your Mr Paint people. Even allowing for dilution those 10ml AK bottles don't go very far!

Regards
Kevin

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Re: What's all this about colour?

Post by Vince Cutajar » Sun Jun 07, 2020 1:35 pm

10ml AK bottles don't go very far!
Kevin, I was pleasantly surprised. I did the whole camouflage of a Tiger 1 using (if I remember correctly) 7 or 8 bottles. I thought that I would need more.

Vince

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Re: What's all this about colour?

Post by Kevin Hunter » Sun Jun 07, 2020 1:51 pm

Hi Vince.
I don’t want to hijack Stephen’s original post too far off topic, but I think part of the problem is I am still learning. How to use my airbrush, size of needle, ratio of paint to thinner, apply too thick, too thin, and so on. I like the AK paint, I just have to use it better. :D
Kevin

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Re: What's all this about colour?

Post by Vince Cutajar » Sun Jun 07, 2020 2:00 pm

Kevin

I was in exactly your situation end of last year. Lots of practice on paper and scrap sheet metal with basecoat. I have never seen the mix ratio for the paint. When I asked the local agent here he said 40% paint and 60% AK thinner. I used 50/50 instead.

Vince

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Re: What's all this about colour?

Post by Greg Clement » Thu Jun 11, 2020 11:59 am

Stephen thanks for a very interesting post. I was getting extremely frustrated trying to find an accurate Nato Green.

One small observation, at the end of Example One you refer to the up and down arrows which allow the ratios of the paints to be altered. However, if you press the Calculator icon it alters the ratios for you to get a much lower Delta value.

Apologies if you have pointed this out somewhere else in the post.

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Re: What's all this about colour?

Post by Stephen White » Thu Jun 11, 2020 1:47 pm

Greg, I forgot that point so many thanks for pointing it out. I've edited the post accordingly. I'll see if Kian would like this to be a Knowledge Base Topic.

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Re: What's all this about colour?

Post by Armortek » Fri Jun 12, 2020 11:42 am

I've just created a Knowledge Base Topic from this thread and added Kevin's Khaki Green No3 example to my original post. Stephen

http://www.armortek.co.uk/Forum3b/viewt ... e427d978bf
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Re: What's all this about colour?

Post by AlastairCooke » Wed Jun 17, 2020 11:00 am

Hi Stephen,
Very interesting post. You have not mentioned 'scale effect'... the fact that a small scale model will need to be painted in a lighter 'colour' if it is too look correct close-up. I am a long way off painting F01 but am interested to know if this scale effect is not an issue at 1/6.

Alastair

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Re: What's all this about colour?

Post by Adrian Harris » Wed Jun 17, 2020 11:05 am

I don't know that anyone has covered scale effect at this size, but a 1/6th scale tank is roughly 6 times larger than the usual 1/35, so it would seem logical that the scale effect ought to be 6 times less apparent.

Unless light and shade operates as a square law, in which case my head will explode..

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Re: What's all this about colour?

Post by Robert Reid » Wed Jun 17, 2020 12:51 pm

Great Read!

BTW, had never heard of AK paints, until I was restoring a Sokolov mount for a 1910 Imperial Maxim gun and needed the 'soviet' green for WW2.

AK had some aerosol that I bought from a hobby shop in Texas via eBay... and it looks dead nuts! Applies well and is just right. Really quality paint!

Excellent article!!!

Cheers,

RPR

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