Changing resolution gets screen darker
 

Hello,


It's been a long time I ever asked for technical
help on a forum. I'm a little lost right now
about where to ask, but the problem started
when I realized recently that anything in
Dosbox would be slightly darker in fullscreen
mode, not enough to not be able to play, but
enough for it to be annoying.


I then realized that my computer also gets "darker"
when I change the screen to a lower resolution.
Recently, I had played with my NVDIA settings
to get better brigthness and colors, so maybe
I switched something wrong, but there was never
any difference of brightness before when I switched
resolutions.


In a standard Dosbox config, when I switch
full resolution and windows resolution to my
current computer resolution (1152X864), and
change output from "surface" to "overlay", the
image is perfect. That's nice, but doesn't explain
my problem, and not helpful if I want to run
a Win95 Cd in 640X480 resolution (right now I use
gapa to change the brightness, but I didn't need
this before).


Does this problem ring a bell to anyone?
I could just put all my NDVIA settings to
default, but I want to wait before I do this
to see if there is something else I'm missing.
Thanks!

Just a guess, but maybe you changed the color channel from all to any one of the three, or the graph in color settings. I never really touch those as the brightness on my laptop is good as it is.

How big is the difference? It can be normal when resizing and applying anti-aliasing that the color gamut gets shifted a little bit.

Thank you both for your replies.


Scatty:

I checked, but all channels are ok in
NVDIA (you mean red, green and blue,
I think?).


Japo:

If you open gapa, and play with the brightness,
it's like 10% less than 0%. I had never seen such a change
before, and it's annoying enough that colours aren't
fresh. It's like noon looking 7 PM in The Black Gate.
(if you get my drift, lol).


Oh, em: What is anti-aliasing? ;-)

From personal experience, some screens need you to play with the screen option system which is incorporated inside the screen itself and cannot be modified directly thru the OS. Other screens also "remember" different settings for different resolutions.

My advice would then be to try to change the brightness directly on the monitor when you switch to fullscreen or other resolutions and then check if the brightness of your native resolution is affected by this change.

Aliasing is something that can happen when you resize an image, and to fix it anti-aliasing is applied, which can have other modifying side effects.

https://en.wikipedia.org/wiki/Aliasing

Flat screens have only one single resolution, as opposed to old CRTs, so every image is resized to this native resolution. This can be done by software, by the graphic card with whatever settings you have, or by the screen itself if it finally receives an image at a different resolution.

I actually seem to recall old CRTs displaying different brightness depending on resolution.

Thanks, you guys. And I do am using an old
quite large CRT: I just love the "retro" experience.
I just never noticed as important changes in brightness
as of very recently.

I'll look into what anti-aliasing cause might have this effect,
but just to respond to Eagle Of Fire: that's a weird thing, in
that when I use Gapa or NDVIA settings while in Dosbox (or
different rez) and adjust the brightness or gamma, I get a
"whitewashing" effect (or polarization, not sure how to say it).
At max, the screen gets all greyish instead of white, like the
screen refuse to "lighten up", in fact just like a dying monitor.
But if I switch the resolution within Dosbox config, the screen
is as bright as it normally is. So I'm discarding the possibility
that the monitor is simply dying, but...


I see something about "augmenting the PPP" parameters
in the screen prefs, but not sure what it means.



EDIT:

Fixed!!!!

Ah well, it's a little embarassing, but...
It's just the monitor refresh setting in NVIDIA.
It was at 60 hertz. Switched it back to 85 or so,
and everything went back to normal (no diff
whatsoever when switchng resolution). Only
weird size and pincushion effect to adjust on
my main resolution, but all is pretty now.


I recall having changed the monitor refresh
setting to 60 hertz, because of an obscure
Windows 3.1 Cd-Rom that was very difficult
to get playing, and the graphics were always
very polarized. Someone had suggested me
to change the Hertz, though later I realized
I just needed to toggle between desktop
and program to have the graphics look fine.
And of course I forgot about the 60 Hertz,
but maybe something else is involved because
I only noticed the problem above quite recently.


At any rates, in case anyone comes up with
a similar problem, you can check that or color
channelling first.


Cheers! And thanks!


Edit2: Well, ok, a couple hours later, I can notice a slight
difference in Dosbox from small window to fullscreen (using
ALT + Enter), but not as bad as before. The Dosbox image
is never as good as when I just config it to my current resolution. Something else I noticed about the text in Dosbox when it begins to run: when I ALT + Enter to fullscreen (or config to fullscreen=true and resolution to original), the text has slight lines into it, a little like a old "interpolated" monitor effect (I'm thinking of the graphic options in the emulator Gens), and it is slightly greyish, and when I just config to
my current resolution, the text is paper-white, very
vibrant and clear. It's probably always like this, but
I never noticed that before. I guess it's really best in
Dosbox to always configure to current resolution, but
then you can't reduce the window. Ah welll....

If anyone want to experience this, tell me if you see
graphic differences (in the quality of the Dosbox
command text when it starts). Thanks!

I always play fullscreen as I consider window playing "inferior". It's also part nostalgia since I really liked that DOS prompt on my very few first computers. Windows is graphically way better of course but the DOS prompt had that customization niche which always attracted me.

So in fact there might be a difference for me but when I go fullscreen in DOSBox it is as exact as I remember it was back in the days. I can't see a difference this way and I would not bother to check the difference between fullscreen and windowed.

Plus, I do have a serie of buttons on the front of my CRT monitor and I can adjust all the settings there on a spot. :p

If you say you're using an old CRT, maybe it's not entirely compatible with all of the digital signals the graphic card sends to it, depending on how old that CRT actually is.
I remember that when I got a Pentium 4 many years ago and tried to connect an old CRT to it, which I used without problems on an old Pentium 100 previously, it didn't work with that Pentium 4. No display no matter the resolition, I specifically tested later. A new CRT I got after worked without problems, though.

Might have to do something with analogue / digital signal connection, I think older CRT's used analogue signals and somewhere at the year 2000 plus minus (maybe already 1998), graphic cards began using the digital signals, which became the standard for CRT monitors.

Edit: look here for a short info.