Photographic "Colour" in Monochrome Images

Jim made a very pertinent comment on the second part of Tomahawk colours which I'll respond to here rather than add a lengthy comment to that thread.

The appearance of that photographic image is pretty consistent with Mr Bowyer's description of "duck egg green" where he implies that "Sky" (the spinner and fuselage band) was lighter and also with F/O Bingham-Wallis who described the RAF-applied fuselage band on the Buffalo as a shade lighter than the factory applied sky blue undersurfaces. However, as will be seen in Part 3 there are other photos of similar RAF Tomahawks that display much less contrast between these colours.

A couple of points to note on this. The first is my old soap box of paint colour standards versus applied paints. Although Sky appears in the standards as a surprisingly dark and saturated colour it is apparent that in practice (and as suggested by Mr Bowyer) the paints could be quite light, appearing almost white in some colour photos. The UK manufactured paints had a high proportion of white extenders and tended to fade and chalk more rapidly (a characteristic which is the subject of criticism in a couple of RAAF reports as well as observations by Messrs Bowyer and Huntley) whereas the Du Pont paints had stronger pigmentation and tended to be more resilient in this respect.

Second is the question of illuminant effect and shadow. Modellers love to speculate and discuss colours based on the apparent tones seen in b/w photographs but the imagery, especially in digitally processed and formatted images, is inherently unreliable. I think too much faith is placed on the tones as they appear in images. Monochromatic tones on film emulsions are not paint - they are just the stimulations on film emulsion of the reflected wavelengths from the variously illuminated surface of paint. One of the best analyses of photographic tonal interpretation was published in Dick Taylor's 'Warpaint' in which he observes:-

"What is crucial is that we must always remember that the tone we see in Black and White photographs is dependent not only on the original colour(s) of the object, but also on the amount of light falling on any one particular area, so areas with tonal qualities (caused by shadows etc) can in fact be the same colour, or alternatively, the same tone can be produced by two different colours."

I would add that the type and direction of illuminant and the type of colour surface also has an effect. In paint the appearance of the colour surface is dependent on the reflected wavelength of the constituent pigments which can and do vary. So that paint colours falling ostensibly within the same family can actually possess different reflective properties. And there is also a difference between film sensitivity to colours and that of the eye.  This is due to the fact that most panchromatic emulsions used are more sensitive to blue, violet and ultraviolet than to other colours so for example blues often appear paler in film than they do to the eye. The degree of blue pigmentation in colours such as these pale blue-greens and grey-greens can have a significant effect on how they appear on film - even before the effects of manipulators like filters are considered. In other words the constituent differences between the factory under surface paint and the RAF-applied Sky, even though visually similar to the eye, could appear tonally very different in a b/w image.  

I don't know why these inherent factors are often so wilfully disregarded in discussions about colour from aircraft photographs but I suspect it is partly due to the strong modelling tendency to try to justify a preferred solution and/or that often deceptive faith in believing your own eyes. In 'Warpaint' Dick Taylor juxtaposes the same image of a British Army tank turret in monochrome and colour photographs. From the monochrome photograph you would swear that the squadron sign and tank name are the same colour because of their apparently identical tone. In the colour photograph it can be seen that the sign is red and the name is yellow!

PS In the schematic above the two dots on opposite sides are identical in tone - sRGB 153 153 153.