>"Warp"  schreef in bericht news:4d13acbe@news.povray.org...
>
>Jaap Frank <jjf### [at] casemanl> wrote:
>> On the contrary, I want to understand why I can't get my three
>> monitors do what Warp and clipka are suggesting:
>> In principle I should configure  those monitors in such a way that
>> the right striped side intensity correspond somewhere in the middle
>> of the right (3.7) strip. I can tell you that's impossible. There is no
>> way I can reach that.
>
>  On your monitor, does the pov3.6 gradient on the left look about linear,
>while the pov3.7 gradient very non-linear (with most of the shades being
>much closer to white than black?

Yes.

> If you look at the picture from sufficiently far away so that the
>patterns on the sides look gray, where would you put them on the pov3.6
>gradient?
>
>  If your answer to the first question is that the pov3.6 gradient looks
>way more linear than the pov3.7 gradient, and the answer to the second
>question is that the pattern looks about the same as the middle of the
>pov3.6 gradient, then I'm puzzled, as I don't understand how that is
<physically possible.
<
<  An idea comes to mind: Double the size of the image (so that the
<horizontal lines on the patterns on the sides become 2 pixels thick),
<check that the pattern does indeed alternate between pure white and
<pure black, and look at the image from even farther away. Does it still
<look the same? Make it 3 times as large as the original (so that the
<horizontal lines become 3 pixels thick). Does it still look about the
<same brightness?
>
>  I'm wondering if your monitor is blurring or antialiasing the pattern,
>causing it to become dimmer. Making the horizontal lines thicker should
>remove that possibility.
>
>-- 
>                                                          - Warp

Answers while sitting on my chair, so distance about 75 cm with
squinting eyes OR standing at a distance of about 4,5 m and wearing
my computer spectacles, so blured again (this workes quit good).
The square numbers are counted from above.
Picture enlarged with Paint Shop Pro 6.

Picture |  Light intensity    |   linearity strips
            | square number    |  impression
            |      3.6        3.7     |   3.6                      3.7
-- 0.75 
m -------------------------------------------------------------------------------
Stamp  |       5           3       | correct                 quit to light
1:1       |       6           4       | just too dark        quit to light
1:2          not possible
-- 4.5 
m ------------------------------------------------------------------------------
1:2       |      7            4/5    | bit too dark         too light
1:3       |      7            5        | bit too dark        bit too light
1:4       |      7            5        | too dark             just too light
1:5       |      7            5        | too dark             just too light

Conclusion: It makes a rather big difference if you are close,
or further away.

Curious about the antialiasing I did put three spectacles on
top of each other and got a very good blow up of my screen
pixels.
With 1:1 the pixels are correct black and white, BUT black
coincide with square number 2, so not totaly black and white
with square number 10, so just not totaly white.
The pixels of the 1:2 until 1:5 pictures were totaly black
and white, so no antialiasing here.

I would say, problem nearly solved. Do the gamma test from a
good distance away from your monitor and blur good.
The linearity of 3.6 looks better then that of 3.7, but 3.6 is just
too dark and 3.7 is too light. Mind that this is for my monitors
which are LCD / TFT monitors.

Jaap

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