6:55:06 PM 
more on textures
Hi Marc,
I will do a little thinking out loud here. As usual I understand you will mine these thoughts for anything useful -- but feel free to discard any or all of it.
I think we should speculate that a texture of lower contrast
becomes visible (light tones) discernibly slower than a texture of higher contrast.
Likewise we should speculate that a texture of lower contrast
becomes invisible (dark tones) discernibly faster than a texture of higher contrast.
That could be a wrong guess, but it seems probable and easy
to check.
If it is true, then which luminance range do we chose
for a standard texture? Seems arbitrary. Maybe emergence times
for maybe three textures with a range of luminance ranges. that sort of information
would also begin to describe a toe and/shoulder on the paper.
Following this a little further, I can imagine a scenario where a texture with more
contrast is discernible as a texture but a texture of less contrast
is no quite a perceptible texture -- more like a gray tone.
Perhaps, conceptually, with the proper selection of luminance range(s), that
scenario is the one that is noted as the definitive emergence time:
light gray (dense negative) -- print values around zone 8:
- condition 1) texture a is only a gray (solid looking)
- condition 2) texture b is a perceptibly a texture.
(I am less clear about the practicality of dark tones)
dark gray (thin negative) -- print values around zone 2
- condition 3) texture c is a perceptibly a texture.
- condition 4) texture d has become solid looking
Not sure here whether texture b needs to be the same for both, but am
taking that as a starting point. I am also not sure if I am thinking about three
textures in this wanderment or two textures or four textures. My guess is four or more.
That then begs the question of how much the paper contrast goofs the
anticipated behavior -- will keep noodling this. Obviously the paper contrast is going to
cause the overall (i.e.. average) dark tone texture densities to vary. In other words,
a paper of high contrast will need sets of average densities (forgetting the luminance range
within each texture for the moment only) that are closer together than low contrast papers.
An approximate rewording of the forgoing is that high contrast papers will be need
textures of lower *average* density than lower contrast papers.
Amongst many characteristics of a texture, two are:
- contrast, i.e. luminance range, within a given texture (film)
- average density within a given texture (film)
The contrast I think we can standardize, even if arbitrarily. The
contrast range of the paper is largely what we are after. We will
need many sets of textures. Those sets may be grouped into
calibration groups useful for marking the conditions sited earlier.
There is a special texture within a calibration group (the one that either
just appeared or is about to disappear depending on whether the
tone in question is light or dark). The special texture has an average density.
The paper contrast is somewhat defined by the difference in contrast between the
average density of the emerging density and the average density of the
almost disappearing density.
We still have to work out how much exposure time though.
I might have just worked myself back toward min_exp_time_to_max_black.
Apologies, I probably see this more clearly than I am wording it, but
have to go.
All of this will vary in part with the paper developer and development time too of course.
Lewis
ps. The luminance range of the reproduction (print) will vary dependant on the paper contrast range Textural luminance should be tuned to the negative. I do not currently have a clear insight into average contrasts of textures on papers of varying contrast range. Perhaps that is a notable characteristic of a texture -- for instance: how does it look when it is perceptibly a texture and has a certain average density (paper). I cannot quite see through that relationship right now.
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