NOT the final answer on Colour

Geoff – I am afraid that to my mind your definite position is an approximation.

if you understand the concept of colour space – a 2D space with a and b cords with a 3rd axis of L from black to white creating a 3D space that encompasses all colours- you will comprehend a near infinite number of colours.

Any systems of chips and colour standards (e.g. Pantone) – will only be spots within this space and any match to them – an approximation.

In addition – to measure a colour you need a light source, a sample and an observer. Unless all 3 are standardised – it is an approximation.

In archaeology an approximation may be sufficient. In industry – an approximation is not good enough e.g. car touch up paints…

I cannot see how a set of colour chips can be seen as Hyper accurate – unless observed in an observation cabinet with a defined light source and then defined further with colour offsets – such as 2r 3d (2 shades red and 3 shades dark).

I can see them only as a hyper quick and fit for purpose – within a certain area.

To further impair colour comparisons ;

FYI – did you ever look at the eyes of an old man and see that they are slightly yellow – this is called macular pigmentation and is a process that starts in all humans in mid age onwards. It is a degenerative process and means that you observation of colour starts going yellow compared to when you saw it when younger.

Also 0.5% of females are colour blind. 8% of all males are colour blind.

I am not colour blind – I pass all the standard tests e.g. Ishihara. When tested on a full colour scale – I have a slight green anomaly 4 colours offset in 96 – that means that my colour perception in that area is different to yours – before the effect of age.

Also as there are 3 colour receptors in your eyes – colour blindness means that generally only one of them is on the blink – hence there are several types of colour blindness – dependant upon which receptor is U/S.

Colour matching can be done against chips- but it is a an approximation!

When you scan and get colour coordinates – unless there are a great many chips (several thousand) there will nearly always be a delta E – which can make a huge difference to the most perceptive instrument available – the human eye.

Thanks for the discussion.

Andy my monitor is not for travelling!

Elliot to colour measure you need a colour measuring device – a colorimeter.

When I studied colour science at Uni – there were bench top and hand held devices.

Manufacturers were Hunterlab , Macbeth and Minolta

Hunterlab are still around as are Minolta

http://www.konicaminolta.eu/measuring-instruments/products/colour-measurement/chroma-meters/cr-400-410/introduction.html?gclid=CMns-L2hpqYCFY9O4QodWj79Xw

http://www.hunterlab.com/

I always liked the hand held Minolta.

Essentially you need a device that will give you a measurement in colorspace – L.a.b. with chroma and hue. This is the unique colour coordinates in the 1976 CIE Lab colour space.

http://en.wikipedia.org/wiki/Lab_color_space

Now you have a colour – how do you match it.

When comparing any approximate colour you test against the same value and get a Delta E ( Emphladung ?) as the difference in colour between two points. Unfortunately if I recall colour space is non Euclidean – If I recall a general rule was a delta E of 1 or 2 was close enough that you would not see it.

If you are trying to colour match against a sample from a 60 year old paint – then you will get the colour coordinates for the aged paint – as Andy knows from his Sky paint discussions – when you age something – the colour changes.

So to match a modern colour formulation- you have to make test samples and age them in a Xenon Arc to evaluate how the compare.

Unless of course it was just for the short term- so match against the aged sample and cross your fingers it doesnt move…

A final point is that you have to assess the light source – D65 is the normal. But if you view under different lights – e.g. Tungsten, Cool White Fluorescent, TL84 etc – the colour you see may be different – this is called metamerism.

If you don’t have a colorimeter in you cupboard – you can either –

1. Get a test flake of paint and use a UV/Vis spectrophotomer with a reflectance chamber inside.
2. Got to a University with a colour lab and test it there.
3. Find a paint manufacturer ( International/Dulux/Crown) and blag them to test them.

Apologies for the detail – it was my Degree and PhD speciality.

LW206 I am in no way debating the validity of your panel!!!!!

It is definitely an RLM paint on a Do17 panel – as vouchsafed by Andy and others!

I have – my apologies – added some thread drift to discuss the colour as observed in your initial photograph vs the RLM standard and why I could not initially see it as a lower airframe paint.

I was also trying to add some humour into what had become a terse discussion on validity. But I again apologise if I had again hit the same nerve.

Purely out of interest – I attach a photo of the bottom of a Ju88 panel that I have repainted in RLM 65 and the original Do17 panel photograph.

The RLM65 I used is exact against Ullmann’s colour chart and was purchased from an RLM paint match company in Germany.

Apologies it is slightly out of focus – the camera was focussed on the KG30 adler further up the panel.

I hope how you can see how we confused it for a green colour.

I re calibrated the screen to see if it would look more blue – but no luck…

I have a statcounter on my website and I had been seeing a lot of hits first from Hornby and then from a toy company in China on MacRoberts Reply page.

Coincidence ?

Cees – Excellent work as always.

I see that it is Lexan – polycarbonate that you are using – stronger and more flexible than acrylic (polyacrylonitrile). I use the same.

Just be careful with the solvents when you paint as it solvent crazes very easily.

Steve – Interesting that you put Christians and then Catholics as separate religions.

Any reason as pre reformation all Christians were Catholics.