Re: [ATM] How dark is dark?

[Richard <cnc@cncservo.co.uk>]

Hi Michael,

Tuesday, September 26, 2006, 4:57:52 PM, you wrote:

MW> The densitometry from gloss and matte photographic may be 
MW> missleading.  The readings would depend on the angle of incident
MW> light and the optics of the densitometer.

Exactly. What we are talking about here is Specular (gloss)
versus Diffuse reflectance (matt). As the specular reflectance
is concentrated into a narrow beam it is bound to be of much
higher intensity than that from a diffuse surface. If the
reflectometer misses that beam of course it would wrongly look
like a much lower overall reflectance.

Look inside any professional optical instrument and you will
find dark diffusely reflective surfaces, often employing
mechanical means to further trap and randomise the reflected
light, such as velvet ansd similar. Do people really think Zeiss
and the like do this for fun?

-- 

Best regards,
  Richard in the UK

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