"clipka" <nomail@nomail> wrote:

> That's a perfectly correct observation: Setting your operating system's
> display resolution to something other than the monitor's /native
> resolution/ will cause the monitor to perform interpolation...

Yes, that occured to me as well (even though I didn't know or remember about the
documentation alluding to it.) In my case, I had changed my 1920 X 1280
monitor rez to 1600 X 900-- the obvious root cause of the problem. (The easiest
way around this is for me to do the gamma calibration at the native
resolution, *then* change it to 1600 X 900.)
>
> ...which means averaging pixel values. Depending on how this is
> implemented, it will  rarely be a linear interpolation of physical
> brightness.
>
Indeed; the 'gamma' video you posted previously-- with its explanation of a
'darkening' effect when blurring colors in gamma 2.2 space-- was on my mind when
I was writing my post ;-) My experiment of reducing the visual size of the gamma
chart (on the monitor)-- and seeing a darker result for the chart's horiziontal
lines-- now seems like a direct result of that. Although, it didn't occur to me
that such a thing happens at the monitor/graphics driver level; I naively
thought it was the fault of my image-viewer apps.
>
> (The striped pattern in itself is a means to force linear interpolation of
> physical brightess: Squinting your eyes a bit, your vision is blurred,
> blending the black and white stripes to a uniform patch of grey with the
> same total brightness.)
>
Yep, that's how I've always done it-- sometimes standing back as far as 15 feet
from the monitor, then blurring my eyes (which isn't difficult, at my age!)
>
> While this fact is indeed not mentioned in the reference section, the tutorial
> section on gamma handling (?.3.4) does sport a note to this effect.
>
I'll take another look there; I must have glossed over that bit of info.

This 'non-linear' blending/blurring phenomenon on a typical gamma 2.2 monitor
could conceivably have deeper ramifactions-- for example, when rendering
a particular kind of scene in POV-Ray. Here's a thought experiment: Let's say
that a flat surface there, facing the camera, has a gradient-y pigment or
'normal' pattern applied to it-- a very *small* pattern with a 'sharp' color_map
and high frequency, like ...
[0.5 rgb 0]
[0.5 rgb 1]

If that object is positioned way off in the distance (relative to the camera), I
could forsee it having a *darker* blended appearance in the final image than if
it were closer to the camera (where the alternating black/white pattern could
actually be seen as individual lines.) Due solely to the 'non-linear' blending
by the monitor of the black/white combination. Micro-normals come to mind as
well, the darker blending effect depending on the orientation of the object and
its distance. But all of this is guesswork, of course.

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