Digital BW, The Print

On 10/16/2012 05:00 AM, David wrote:
> A matte surface is made up of lots of little surfaces facing
> lots of directions, and so some light always gets reflected forwards. If
> we put a piece of glass in front of a matte surface, most of the light
> from the side is reflected to the other side, increasing the apparent Dmax.

Is that actually happening?  I always thought that there is a loss of 
light when glass is put in front of a print, the more when the distance 
from the glass to the print is wider and/or the glass quality is lower. 
Compared to a bare matte print viewed in the same light you will see 
less separation in the shadows but the dynamic range is not altered as 
the paper white will suffer of that light loss too. A Diasec mounting 
with the print front faced is a completely different method that will 
make a matte paper into a gloss paper more or less and then Dmax and 
dynamic range will increase. More light on a framed print should bring 
back the same sensation a bare print gives with lower light, 
anti-reflective museum glass a must then. That is the other aspect, 
glass reflections will interfere more with the shadow parts of an image 
than with the highlights.

>  What I think that I am
> starting to appreciate is that the loss of deep shadow density on the
> matte paper is balanced by a greater tonal range in the highlights. Some
> of this may have to do with the brightener in this paper, but the glossy
> papers I use have OBAs, too. I think that the relative effect on the
> highlights is the complement of what happens to the shadows: more light
> from the sides is reflected forward from the matte paper.

Is matte omnidirectional reflection of the light not creating a simple 
flare on the total of the image? Having a higher impact on the black 
densities of the picture than on the highlights like in all situations 
where flare happens? It is more a diminishing of the total dynamic range 
but more in shadows than in the highlights so no actual gain in the 
highlight separations either. I think profiling based on a linearisation 
made with 45/0 degr. spectrometer + a perceptual algorithm will create 
equal perceptual separation in the tones in almost all paper surfaces. 
The optical geometry of the spectrometers is not the ideal Ulbright 
sphere but not bad either. I have written before that bronzing can 
affect color reading with today's desktop spectrometers but that is a 
more exotic issue.

-- 
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
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