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FractRacer <lg.### [at] gmail com> wrote:
> The image seems normal, it is like povray has rendered, it is a night
> scene with a shining star...
> Is, for you, the center of the star white? And the trees dark? If yes,
> all is right.
Yes, that's how it appears to me. The thing that made me question your image's
appearance (on my system) is that I thought I was missing the 'details' of the
image. I took it into Photoshop and used 'levels' to brighten it up somewhat,
and was able to see many more details-- which is what I thought everyone else
was seeing ;-)
> Have you seen the image of Kurt Le Pirate: black and white stripes?
> How appear this image on your screen?
That one appears perfectly normal. I didn't think to check if it was a .png
image; I'll take another look.
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Ger <No.### [at] ThankYou> wrote:
>
> Or for a CRT you could also use http://www.displaycalibration.com/
>
Thanks. I'll check that out. (Before now, I haven't *noticed* any odd problems
with my monitor-- but calibrating it is a good idea.)
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"Pekka Aho" <pek### [at] gmailcom> wrote:
> My latest image was actually quite dark already to begin with, thus what I see
> in the .jpg now here on my end doesn't differ at all from the original .png file
> that I posted.
Thanks; that's a relief to know. (Nice image, BTW!) As I mentioned in another
reply here, I thought I was missing some details that others were seeing (based
on their comments about your image.)
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Alain <kua### [at] videotronca> wrote:
>
> I also have a CTR monitor, and those images also look dark on my side.
> With CTR monitors, you NEED to set the brightness quite low, often to
> the lowest setting, to prevent bluring and bleeding. That's not the case
> when using LCD, or plasms, monitors.
>
> "Normal" settings for CRT are usualy contrast at the highest value and
> brightness set so that a totaly black display stays /just/ black. With
> those settings, the dark images are very dark unless brightned using
> post processing.
That thought occurred to me, that the differences between CRT and LCD/LED
monitors might be part of the problem: creating the image on one type of
monitor, but viewing it on another. Years ago, I bought an LCD monitor-- but
took it back within days, as its color rendition/contrast were just too...
'different'... from what I was used to on my CRT.
>
> As for your images, YOU created them much brighter BECAUSE your display
> is darker.
>
I was wondering about that, too-- even whether my .jpeg screenshot image here
might look different (brighter) on other peoples' monitors than my own!
Posting .png images is something I rarely do (if ever?); I should do a test and
upload a .png here, to see if the *posted* result matches its original
appearance on my system. (But more importantly, to see if its tonal range
matches the 'overall appearance' of other .png's posted on the newsgroup.)
The last POV-Ray image I made and uploaded was my 'matchmoving' experiment, as a
..jpeg-- found here...
http://news.povray.org/*/attachment/%3Cweb.52fd49177094def7c2d977c20%40news.povray.org%3E/matchmoving_still_frame.jpg
On my own system, that one looks identically the same on the newsgroup page (and
as a download) compared to my original. But does it possibly look 'washed out'
on your monitor (and/or on LCD monitors)? That's a subjective question, of
course, but it would be helpful for me to know.
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Ger <No.### [at] ThankYou> wrote:
>
> Or for a CRT you could also use http://www.displaycalibration.com/
>
WELL!!
I'm embarrassed to say that my CRT monitor was *not* well-calibrated, when I
*thought* it was OK. I followed the procedure on that page (and also re-ran my
'Adobe gamma' app, as well as looking again at POV-Rays' gamma documentation
image), and the results are MUCH better-- I can now see the details in the two
..png's that I posted about. (Before, in FractRacer's image, I couldn't see any
details in the background-- the mountain and the dark blue sky were nearly
black!)
Lesson learned: I shouldn't assume that my system is always running perfectly
:-O
So sorry to give FractRacer and Pekka Aho a false impression of their images.
Thanks, everyone, for helping me out with this. I'll be MUCH more careful in the
future ;-)
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"Kenneth" <kdw### [at] gmailcom> wrote:
>
> So sorry to give FractRacer and Pekka Aho a false impression of their images.
>
No worries at all! =)
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On Thu, 10 Apr 2014 23:53:16 EDT, "Kenneth" <kdw### [at] gmailcom>
wrote:
Have a look at this web page or search for "grey scale step wedge"
http://www.pbase.com/jackcnd/1080p_tests
in particular look at the greyscale step images. On a properly
calibratedhigh quality monitor you should be able to see and
differenciate all the steps.
I hope this helps
John
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AQ <AQ### [at] worldcom> wrote:
> On Thu, 10 Apr 2014 23:53:16 EDT, "Kenneth" <kdw### [at] gmailcom>
> wrote:
>
> Have a look at this web page or search for "grey scale step wedge"
>
> http://www.pbase.com/jackcnd/1080p_tests
>
I'm happy to report that my monitor now passes *all* the tests there. Thanks for
the link.
The underlying problem was... human error, naturally. Sometime in the past--
maybe more than a year ago!-- I had actually reduced the brightness AND
contrast-- for the sole purpose of trying to avoid 'burning in' my monitor's
phosphors (IIRC.) That was my thought, anyway-- based on *old* and probably
out-of-date info from decades ago. Then I forgot that I had done it!
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Am 10.04.2014 20:58, schrieb Kenneth:
> I'm beginning to think that there is something wrong with my computer/monitor
> set-up (Windows XP on a CRT monitor): The .png images that various POV-Ray users
> are uploading to the newsgroups look 'dark' on my system, and I have no idea
> what the cause is. (Well, I'm guessing that the images *should* look brighter,
> although I don't know for sure.)
There are various possible reasons:
(A) Personal preference.
Some people simply love playing with darkness and light, and the images
may be intended to be that dark, while you may prefer images to have
less contrast.
(B) Your "display gamma".
In a nutshell, no two computer/display combinations natively show the
same image in the same way, due to hardware tolerances, manufacturer
preferences, and brightness/contrast control settings.
The only way to make sure your computer display shows .png images
exactly the way they are supposed to be (according to the file format
specification and the data in the file) is to /calibrate/ your display,
which in essence means that you teach your computer to auto-correct for
your display's peculiarities.
While proper calibration would require a colorimeter (and would also
account for hue and saturation issues), if proper brightness is all you
want then simple /gamma correction/ will suffice; most display hardware
I know of comes with tools to perform gamma correction, and if I'm not
mistaken Windows 7 and later (maybe also Vista) comes with such tools
onboard.
(C) The author's display gamma.
Just as you can't be sure /you're/ seeing what's officially encoded in
the .png file unless /your/ display is calibrated, you can't be sure
that what's officially encoded in the .png is what the /author/ was
seeing unless /their/ display is calibrated as well. However, in most
cases this is obviously outside your area of influence.
(D) Your display's "black level".
Your display may be unable to show the same level of black that the
original author saw, which might "drown" some almost-but-not-quite black
details. However, while this is a common issue with LCDs, it is rarely
seen in CRT displays.
In real life it's typically a combination of (A)-(C), as well as (D) for
people who have an LCD.
> This dark appearance shows up in a range of applications, not just a specific
> one-- the latest Firefox (v28.0); my older Photoshop; and in Windows' Picture
> And Fax Viewer. My own .png images made in POV-Ray look fine on my system, as do
> ...jpegs.
>
> To better show this, I've made .jpeg screenshots of two recent uploaded images,
> by FractRacer and Pekka Aho. They are accurate reproductions of how the .png
> originals appear on my end. Can someone compare my .jpegs to the original
> uploads, to see if they visually match?
How on earth do you know that those JPEGs are "accurate reproductions of
how the .png originals appear on [your] end"? After all, you'd need a
calibrated display in the first place to be sure that what's encoded in
the JPEGs accurately reproduces what you saw.
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> Am 10.04.2014 20:58, schrieb Kenneth:
>> I'm beginning to think that there is something wrong with my
>> computer/monitor
>> set-up (Windows XP on a CRT monitor): The .png images that various
>> POV-Ray users
>> are uploading to the newsgroups look 'dark' on my system, and I have
>> no idea
>> what the cause is. (Well, I'm guessing that the images *should* look
>> brighter,
>> although I don't know for sure.)
>
> There are various possible reasons:
>
>
> (A) Personal preference.
>
> Some people simply love playing with darkness and light, and the images
> may be intended to be that dark, while you may prefer images to have
> less contrast.
>
>
> (B) Your "display gamma".
>
> In a nutshell, no two computer/display combinations natively show the
> same image in the same way, due to hardware tolerances, manufacturer
> preferences, and brightness/contrast control settings.
>
> The only way to make sure your computer display shows .png images
> exactly the way they are supposed to be (according to the file format
> specification and the data in the file) is to /calibrate/ your display,
> which in essence means that you teach your computer to auto-correct for
> your display's peculiarities.
>
> While proper calibration would require a colorimeter (and would also
> account for hue and saturation issues), if proper brightness is all you
> want then simple /gamma correction/ will suffice; most display hardware
> I know of comes with tools to perform gamma correction, and if I'm not
> mistaken Windows 7 and later (maybe also Vista) comes with such tools
> onboard.
>
>
> (C) The author's display gamma.
>
> Just as you can't be sure /you're/ seeing what's officially encoded in
> the .png file unless /your/ display is calibrated, you can't be sure
> that what's officially encoded in the .png is what the /author/ was
> seeing unless /their/ display is calibrated as well. However, in most
> cases this is obviously outside your area of influence.
>
>
> (D) Your display's "black level".
>
> Your display may be unable to show the same level of black that the
> original author saw, which might "drown" some almost-but-not-quite black
> details. However, while this is a common issue with LCDs, it is rarely
> seen in CRT displays.
>
>
> In real life it's typically a combination of (A)-(C), as well as (D) for
> people who have an LCD.
>
>
(E) Your display's "white" level.
Many CTRs tend to get blurry when the white level is set moderately
high. This forces the user to greatly reduce the overall brightness,
often to the minimum possible level, to prevent the bluring of text and
the eye strain it will cause.
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