Digital BW, The Print

Hmmmm  This is interesting.  I am happy to proven wrong on this but I still
don't believe that the greater dMax of photo paper is purely attributable to
the way it is measured.  I agree that because matte paper scatters the light
produced by a densitometer more so than photo paper that all else being
equal the chances are that more light hits the sensor at 45 degrees even if
the total amount of reflected light is the same for both.  But if you have a
perfectly diffuse light source then the reflection characteristics (in terms
of the angles of reflection) of matte paper and photo paper converge.  Light
is hitting both from all angles and being reflected at all angles.  I do not
believe that a matte black square and a photo black square look the same
black under very diffuse lighting sources.  For any given surface this
property could arguably be measured by comparing readings from a d/0 degrees
(diffuse light source) instrument - excluding the specular component.


> From: <hogarth@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 25 May 2005 15:07:58 -0400
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Matte versus glossy dmax: a matter of physics?
> 
> davelongviews wrote:
> 
>> There has been a lot of discussion over extended periods on the group
>> regarding matte and glossy dmax. Is it true that light SCATTERED at
>> the paper surface is what gives a matte surface its look, and that
>> very same scattering is what reduces dmax? And with a glossy paper
>> less light is scattered, more is REFLECTED, dmax is greater, and you
>> have the glossyness to deal with. In other words isn't it true that
>> you can't have a matte surface with a truely large dmax? Aren't paper
>> surface/glossiness and dmax directly related in a way we wish they
>> weren't? Is it physically possible to separate the two? Any thoughts?
>> 
>> Dave
>> 
>> 
> Yes to all. This is explained pretty well in the book /Light Science &
> Magic/ by Hunter and Fuqua IIRC. In the early chapters they cover how
> objects reflect light. I can't find the book right off, so I'll have to
> broadly paraphrase.
> 
> Basically, matte object give a diffuse reflection, while glossy objects
> give off direct reflection. If you are looking at a matte print on axis,
> light coming from anywhere in front of the print is reflected difusely -
> that is, light coming in at a 10 degree angle is reflected back fairly
> equally across a 180 degree hemisphere. Some of this light reflects to
> your eyes.
> 
> If you try that with a glossy print, the light coming in at a 10 degree
> angle is reflected back off the print at 170 degrees. Almost none of it
> will reflect back into your eyes.
> 
> What it all comes down to is, glossy surfaces reflect less light into
> your eyes. It's the essence of being glossy. And it's the reason that
> glossy surfaces exhibit greater Dmax.
> --
> Bruce Watson
> 
>