Jens-Michael Gross said:
Maybe I have been weary after 10 hours of programming and circuit
design. And (despite of your later insulting statements) I took the time
now to find that old posting (no archieve required) you are referring
to.
Yes, I have been wrong, and it was of completely no importance at this
point of the discussion (I could have omitted any value without changing
the statement).
You could only have omitted it by *not* attempting to correct what was
already a correct statement, that the black and white tones were
represented by 9 levels in your conversion!
But you adopted this mistake later to prove your own argumentation.
No, I explained why your mistake was a mistake - at no time did I ever
"adopt" it.
Once again: if you look at the plain numbers alone, you're
mathematically correct. But looking onto the purpose of the whole thing,
you're wrong. because numbers are just a snippet of reality.
You're ASSuming, that black (represented by 0) is the bottom of all and
white (represented by 255) is the peak of all. Thi sis true as long as
your world is the world of numbers alone.
No, it is true in the output level from your video card. 255 and 15
represent the same identical peak white output in their relevant scales
- there is no whiter level. Similarly there is nothing blacker than 0
and this is identical in both scales.
But in this particular case,
the numbers are just representations of brightness levels. And a number
of zero does not mean zero photons and a number of 255 does not mean
infinite photons.
Perhaps you will enlighten us all with your interpretation of an output
level which is darker than 0, in either scale, together with outputs
which are lighter than 15 and 255 in their relevant scales!
And the results I gor with real world data proves me right, no matter
how often you repeat that I am mathematically wrong.
No, the results that you got prove that your video card and screen gamma
are incorrectly set! Recall that I have also implemented both
conversions and found the difference to be negligible other than
slightly a coarser conversion in the mid tones using your preferred
method. Of course, you prefer to accuse me of *not* doing this, which
amounts to no more than an accusation of lying! Still, there is little
hope of you actually reading and understanding my posts when you are
patently unable to read and maintain consistency in your own!
This is about scanners and images and image data conversion. This is not
comp.mathematics or something like that.
Precisely, which is why luminance output and *not* which conversion
produces minimum error against an arbitrary mathematical rounding scheme
is what matters. You are the correspondent which has been continually
referring to one conversion producing a lower error than the other, yet
you have only been able to quantify that error in mathematical terms
against some arbitrary numerical reference, rather than in luminance
terms. Even though this is what occurs when a luminance histogram is
examined, you still claim that the mathematical error is the better
assessment! (If in doubt, see your post of 18th June - requoted here
for your benefit:
"The error range in case of truncation is 0..1, while in case of
rounding it is -0.5..0.5. The error is NEVER bigger than 0.5. This is a
mathematical fact..."
Now who was citing differences of mathematical errors between the
techniques? I seem to recall stating some time back in this thread that
the average error of both methods cancelled out in luminance terms, but
I shall leave that to you to find, and read your own ludicrous responses
to those very words.
Depending on the gamma and the calibration and the color temperature of
the used monitor or the settigns of the printer or whatever, none of the
colors is 'crrect' or 'wrong'. But what looks best IS best - no matter
how mathematically correct the calculation was.
Yes, and with a properly calibrated screen you will find that the even
distribution, giving equal weighting to all of the final tones (instead
of slightly over half the weighting to the extreme tones) results in a
matching image.
And that's all what interests people who want to convert images.
Because your eyes are adaptive and easily to fool?
Can you tell light gray from bright white or very dark gray from black
if you only see one of them?
We are not discussing a single tone conversion, so seeing "only one of
them" is irrelevant in this context. You see the complete tonal range
in both an image and a greyscale ramp, so my question still stands - why
do you consider a ramp to be an unsuitable test, particularly when many
real images actually contain full scale and near full scale ramps, with
and without embedded texture?
Ramps are generated and do not need to be converted. If you need a ramp,
generate it.
By coincidence, I have in front of me a Fuji Velvia image, shot in
Havana last year, of a model standing in front of a doorway in a
whitewashed wall. The dark doorway behind the model, a white walled
hallway, shows a near perfect grey ramp from white just behind the model
to deep black in the building interior. No synthetic generation
involved, a totally natural and not uncommon type of image. So I ask
again, why you find a ramp an unsuitable test and what happens when the
image *is* a ramp?
There are so many exaples of generated images (ramps, checker boards,
crossing lines) where your eyes will tell you that the lines are bent,
the white has black dots and whatever. Or images where the lines look
linear and they are not. Put them through a mathematically correct
conversion and you'll swear that the original and the result are two
completely different things.
We are not discussing optical illusions. That is why a histogram is
important - optical illusions only affect one aspect of the view and a
histogram gives another perspective.
Answer the question - this test is *not* an optical illusion.
What's obvious and what not, there we disagree obviously (or will you
deny even that?)
I never suspected your calculator being wrong, only your use of it.
Liar! I quote (from your message of 27th June):
"You can obviously not even _count_ right."
However, as you have already demonstrated, you cannot get a consistent
result from a calculator from one day to the next - or, for that matter,
understand text which clearly states the paradox that "your argument"
produces.
And gives more than lousy results.
Less lousy than an all black or all white? We can only thank God that
Messrs Floyd and Steinberg arrived on the scene before you did and
managed to develop their method of producing an image when only two
output tines are present!
I don't stick on mathematics if reality gives me a better result.
So why has this been the crutch your argument leans on?
If all people would stick on linear mathematics, Newtons mechanics would
be still state-of-the-art and Einstein would have never written his far
superior theories (which proved much better to explain some but not all
things that cannot be explained at all with linear math)
Its obviously news to you that both special and general relativity *are*
linear mathematics! I suggest you read Einstein's 1905 paper in which
he states that the entire theory depends on the known laws of physics
(and hence the mathematics which underpins them) applies in all
reference frames.
Take some free advice: when you are out of your depth, stop digging!
If you don't know a subject then don't introduce it as an analogy.
) and with current compilers you'd use a 32bit